JP6890932B2 - Imaging device and control method - Google Patents

Description

The present invention relates to an image pickup apparatus, and more particularly to a technique for calculating a light amount change characteristic of light from a photometric object.

In recent years, the sensitivity of imaging devices such as digital cameras and mobile phones has been increasing. Therefore, even in a relatively dark environment such as indoors, it has become possible to acquire a bright image with suppressed blurring by shooting with a high shutter speed (shortened exposure time).

In addition, fluorescent lamps, which are widely used as indoor light sources, cause flicker, which is a phenomenon in which the illumination light fluctuates periodically due to the influence of the commercial power frequency. When shooting at a high shutter speed under a light source that causes such flicker (hereinafter referred to as a flicker light source), exposure unevenness and color unevenness may occur in one image, or a plurality of shots taken continuously may occur. Exposure and color temperature may vary between images.

In response to such a problem, Patent Document 1 is a technique of detecting a flicker state of illumination light and adjusting the imaging timing so that the center of the exposure time substantially coincides with the timing at which the amount of illumination light shows a maximum value. Has been proposed.

Japanese Unexamined Patent Publication No. 2006-22935

However, Patent Document 1 does not consider the case where exposure unevenness occurs only in a part of the imaging region such as an environment in which natural light and artificial light are mixed. In the case of an environment in which natural light and artificial light are mixed, it is difficult to accurately calculate the light intensity change characteristic of the region irradiated with artificial light due to the influence of natural light when the entire imaging region is evaluated.

Therefore, an object of the present invention is to make it possible to accurately calculate the light amount change characteristic of the light from the photometric object according to the photographing environment.

In order to achieve the above object, the photometric apparatus according to the present invention includes a photometric means for obtaining a photometric value of each of a plurality of photometric areas divided into a main subject area in the photometric area and a other area, and the above-mentioned photometric means. A determination means for comparing the brightness value of the subject based on the photometric result of the photometric means and the threshold value, and a weighting degree corresponding to the plurality of photometric areas when detecting flicker are set based on the determination result of the determination means. It has a setting means for detecting flicker based on a photometric value of each of the plurality of photometric areas and a weighting degree set by the setting means, and the setting means is determined by the determination means. When it is determined that the brightness value of the subject is smaller than the first threshold value, the weighting degrees corresponding to the plurality of photometric areas are substantially the same, and the brightness value of the subject is larger than the first threshold value. When it is determined that the value is equal to or higher than the second threshold value, the main subject region is characterized in that the weighting degree is larger than that of the other regions.

According to the present invention, it is possible to accurately calculate the light amount change characteristic of the light from the photometric object according to the photographing environment.

It is the schematic of the image pickup system which concerns on embodiment of this invention. It is a figure which shows the configuration example of the focus detection sensor. It is a figure which shows the relationship between the light-measuring area of a light-measuring sensor, and the focal point detection position of a focal point detection sensor. It is a block diagram of the image pickup system which concerns on embodiment of this invention. It is a figure which shows the operation about the light emission photographing of the imaging system which concerns on 1st Embodiment of this invention. It is a figure which shows the flicker detection process which concerns on 1st Embodiment of this invention. It is a figure which shows the weighting of each metering area at the time of calculating the subject luminance value for flicker detection according to a shooting environment. It is a figure which shows the operation about the light emission photographing of the imaging system which concerns on 2nd Embodiment of this invention. It is a figure which shows the flicker detection process which concerns on the 2nd Embodiment of this invention. It is a figure which shows the flicker detection process which concerns on 3rd Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the following drawings.

(First Embodiment)
FIG. 1 is a schematic view of an imaging system according to an embodiment of the present invention. The imaging system of FIG. 1 includes a camera body 1 which is an imaging device, an interchangeable lens 2 which is a detachable interchangeable lens of the camera body 1, and a camera. 1 has a flash 3 which is a removable lighting device.

In the camera body 1, 10 is a mechanical shutter, 11 is an optical low-pass filter, and 12 is an image sensor composed of an area storage type photoelectric conversion element such as CMOS or CCD. The image sensor 12 is exposed by retracting the mechanical shutter 10 from the optical path.

Reference numeral 13 is a semitransparent main mirror, 14 is a first reflection mirror, and both the main mirror 13 and the first reflection mirror 14 jump up at the time of shooting and retract from the optical path.

15 is a paraxial imaging surface conjugated to the image pickup surface of the image pickup element 12 by the first reflection mirror 14, 16 is a second reflection mirror, 17 is an infrared cut filter, and 18 is an aperture having two openings. Reference numeral 19 is a secondary image pickup lens, and reference numeral 20 denotes a focus detection sensor (AF sensor). The focus detection sensor 20 is composed of an area storage type photoelectric conversion element such as CMOS. FIG. 2 is a diagram showing a configuration example of the focus detection sensor 20, and as shown in FIG. 2, two pairs of light receiving sensor units 20A and 20B are divided into a large number corresponding to the two openings of the diaphragm 18. It is composed of the area of. Further, in addition to the light receiving sensor units 20A and 20B, a signal storage unit, a peripheral circuit for signal processing, and the like are mounted as integrated circuits on the same chip. The configuration from the first reflection mirror 14 to the focus detection sensor 20 enables focus detection by a phase difference detection method at a plurality of positions in the imaging region.

21 is a diffusive focus plate, 22 is a pentaprism, 23 is an eyepiece, 24 is a third reflection mirror, 25 is a condenser lens, and 26 is a photometric sensor (AE sensor) for obtaining information on the brightness of the subject. ). The finder optical system is composed of the focus plate 21, the pentaprism 22, and the eyepiece 23. A part of the light rays reflected by the main mirror 13 and diffused by the focus plate 21 is incident on the photometric sensor 26 outside the optical axis.

The photometric sensor 26 is composed of an area storage type photoelectric conversion element such as CMOS. FIG. 3A is a diagram showing a configuration example of the photometric sensor 26, and as shown in FIG. 3A, the luminance information and color information of the subject are divided into a plurality of regions (photometric areas) in the light receiving region. Can be output. In this example, the plurality of divided areas are divided into 35 of 7 columns × 5 rows, and each of the 35 divided areas is referred to as PD1 to PD35. Although not shown, each divided region of PD1 to PD35 is further divided into finer light receiving unit pixels, and each pixel is provided with a color filter in a fixed arrangement. Subject detection information can be obtained based on the output information of the photometric sensor 26 having such a configuration. The subject detection information may be face detection information of a person based on the detailed pixel output of the light receiving unit of the photometric sensor 26, or color information of the main subject based on the color detection information of the photometric sensor 26. FIG. 3B is a diagram showing the relationship between the photometric area of the photometric sensor 26 and the focus detection position of the focus detection sensor 20. In this example, the focus detection position in the imaging region by the focus detection sensor 20 is set to 11 points from FA10 to FA26, and each focus detection position matches the PD10 to PD26 portion of the metering area by the photometric sensor 26. It is supposed to be.

27 is a mount portion to which the interchangeable lens 2 is attached, 28 is a contact portion for performing information communication with the interchangeable lens 2, and 29 is a connection portion to which the flash 3 can be attached.

In the interchangeable lens 2, 30a to 30e are optical lenses constituting the photographing lens, 31 is an aperture, 32 is a contact portion for information communication with the camera body 1, and 33 is a mount portion for being attached to the camera body 1. is there.

In the flash 3, 34 is a xenon tube as a light source, 35 is a reflecting member that reflects the light emitted by the light source in a predetermined direction, and 36 is a Fresnel lens that collects the light from the xenon tube 34 and the light reflected by the reflecting member 35. Is. Reference numeral 37 is a monitor sensor for monitoring the amount of light emitted from the xenon tube 34, and 38 is an attachment portion for attaching the flash 3 to the camera body 1.

FIG. 4 is a block diagram of the imaging system shown in FIG. 1, and the same parts as those in FIG. 1 have the same reference numerals as those in FIG.

In the camera body 1, for example, 41 is a one-chip microcomputer (microcomputer) having an ALU, ROM, RAM, A / D converter, timer, serial communication port (SPI), etc. built in, and controls the entire camera imaging system. ..

The output signals of the focus detection sensor 20 and the photometric sensor 26 are connected to the A / D converter input terminal of the microcomputer 41. Reference numeral 42 denotes a timing generator that generates a timing signal or the like for controlling the accumulation and reading of the photometric sensor 26.

Reference numeral 43 denotes a signal processing circuit, which controls the image sensor 12 according to the instruction of the microcomputer 41, inputs the image sensor output by the image sensor 12 while performing A / D conversion, performs signal processing, and obtains an image signal. Further, in recording the obtained image signal, necessary image processing such as compression is performed. Reference numeral 44 denotes a memory such as a DRAM, which is used as a work memory when the signal processing circuit 43 performs various signal processing, or as a VRAM when displaying an image on the display 45 described later. Reference numeral 45 denotes a display unit composed of a liquid crystal panel or the like and displaying various shooting information and captured images, and lighting control is performed according to an instruction from the microcomputer 41. Reference numeral 46 denotes a storage means using a flash memory, an optical disk, or the like, and the captured image signal is input from the signal processing circuit 43 and stored.

Reference numeral 47 denotes a first motor driver, which is connected to the output terminal of the microcomputer 41 and is controlled to perform the up / down of the main mirror 13 and the first reflection mirror 14 and the charging of the mechanical shutter 10. Drives the motor 48. Reference numeral 49 denotes a release switch for instructing the start of shooting.

Reference numeral 28 denotes a contact portion with the interchangeable lens 2, to which the input / output signals of the serial communication port of the microcomputer 41 are connected. Reference numeral 29 denotes a connection portion with the flash 3, and the input / output signals of the serial communication port of the microcomputer 41 are connected so as to be able to communicate with the flash 3. Reference numeral 50 denotes a shutter driving means, which is connected to the output terminal of the microcomputer 41 to drive the mechanical shutter 10.

In the interchangeable lens 2, 51 is a lens microcomputer by a one-chip microcomputer having an ALU, ROM, RAM, timer, serial communication port (SPI), etc. built in, for example.

Reference numeral 52 denotes a second motor driver, which is connected to the output terminal of the lens microcomputer 51 and is controlled to drive the second motor 53 for adjusting the focus. Reference numeral 54 denotes a third motor driver, which is connected to the output terminal of the lens microcomputer 51 and is controlled to drive the third motor 55 for controlling the aperture 31. Reference numeral 56 denotes a distance encoder for obtaining information on the amount of extension of the focus adjustment lens (focus lens), that is, the subject distance, and is connected to the input terminal of the lens microcomputer 51. Reference numeral 57 denotes a zoom encoder for obtaining focal length information at the time of shooting when the interchangeable lens 2 is a zoom lens, and is connected to an input terminal of the lens microcomputer 51. Reference numeral 32 denotes a contact portion with the camera body 1, to which the input / output signals of the serial communication port of the lens microcomputer 51 are connected.

When the interchangeable lens 2 is attached to the camera body 1, the contact portions 28 and 32 are connected to each other, and the lens microcomputer 51 can perform data communication with the microcomputer 41 of the camera body 1. Lens-specific optical information required for the camera body 1 microcomputer 41 to perform focus detection and exposure calculation is output from the lens microcomputer 51 to the camera body 1 microcomputer 41 by data communication. Further, information about the subject distance or focal length information based on the distance encoder 56 or the zoom encoder 57 is output from the lens microcomputer 51 to the microcomputer 41 of the camera body 1 by data communication. Further, the focus adjustment information and the aperture information obtained as a result of the focus detection and the exposure calculation performed by the microcomputer 41 of the camera body 1 are output from the microcomputer 41 of the camera body 1 to the lens microcomputer 51 by data communication. Then, the lens microcomputer 51 controls the second motor driver 52 according to the focus adjustment information, and controls the third motor driver 54 according to the aperture information.

In the flash 3, the 61 is, for example, a flash microcomputer by a one-chip microcomputer having an ALU, a ROM, a RAM, an A / D converter, a timer, a serial communication port (SPI), and the like inside. Reference numeral 62 denotes a step-up unit that includes a capacitor and has a function of creating a high voltage of about 300 V required for light emission of the xenon tube 34 and charging the high voltage to the capacitor.

When the flash 3 is attached to the camera body 1, the connection portions 38 and 29 are connected to each other, and the flash microcomputer 61 can perform data communication with the microcomputer 41 of the camera body 1. The flash microcomputer 61 controls the booster 62 according to the communication content from the microcomputer 41 of the camera body 1 to start and stop the light emission of the xenon tube 34, and at the same time, the detection amount of the monitor sensor 37 is transmitted to the microcomputer 41 of the camera body 1. And output.

Next, the operation related to luminescence photography of the imaging system of the present embodiment will be described with reference to FIG. FIG. 5 is a diagram showing an operation related to light emission photographing of the imaging system of the present embodiment, and when the power switch (not shown) of the camera body 1 is turned on and the microcomputer 41 can operate, the operation shown in FIG. 5 starts. Will be done.

In step S101, the microcomputer 41 communicates with the flash microcomputer 61 to operate the booster unit 62 to instruct the capacitor to be sufficiently charged to emit light from the flash 3.

In step S102, the microcomputer 41 communicates with the lens microcomputer 51 to obtain various lens information necessary for distance measurement and light measurement.

In step S103, the microcomputer 41 outputs a control signal to the focus detection sensor 20. Then, when the signal storage of the focus detection sensor 20 is completed, the microcomputer 41 reads the signal stored in the focus detection sensor 20 and performs A / D conversion, and it is necessary to perform shading or the like for each read digital data. Various data corrections are performed.

In step S104, the microcomputer 41 calculates the focal state of each focus detection position in the imaging region based on the lens information obtained in step S102 and the digital data obtained in step S103, and the region to be focused in the imaging region ( (Focus target area) is determined. If there is an area designated in advance by an operation member (not shown) included in the camera body 1, the focus target area may follow the designation.

Then, the microcomputer 41 calculates the lens movement amount for focusing according to the focal state in the determined focusing target region, and outputs the calculated lens movement amount to the lens microcomputer 51. The lens microcomputer 51 outputs a signal to the second motor driver 52 so as to drive the focus adjusting lens based on the amount of lens movement acquired from the microcomputer 41, and drives the second motor 53. The subject in the in-focus target area determined by this is in the in-focus state. Here, since the information of the distance encoder 56 is changed by driving the focus adjusting lens, the microcomputer 41 communicates with the lens microcomputer 51 and updates various lens information. Further, the microcomputer 41 again calculates the signal accumulation and signal readout of the focus detection sensor 20 and the focus state of each focus detection position in the imaging region after the subject in the focus target region is in focus. ..

In step S105, the microcomputer 41 controls the timing generator 42 to perform predetermined storage control and signal reading control of the photometric sensor 26. Here, the first photometric information for subject detection processing and the exposure calculation for determining the exposure at the time of shooting, and the second photometric information for calculating the light amount change characteristic (light amount change period and phase) of the light measurement target. Is controlled so that

In order to obtain the second photometric information, for example, the accumulation control and the signal read-out control are repeated a plurality of times at intervals sufficiently shorter than the assumed light amount change period. The microcomputer 41 sequentially reads a plurality of stored signals from the photometric sensor 26, performs A / D conversion, and stores the stored signals in the RAM.

It should be noted that there may be an example in which the accumulation for obtaining the first photometric information and the accumulation for obtaining the second photometric information are performed independently, and the photometric information obtained from the accumulation for obtaining the second photometric information. Can be added to obtain the accumulated information for obtaining the first metering information.

In step S106, the microcomputer 41 performs subject detection processing and exposure calculation processing based on the first photometric information stored in the RAM. The subject detection process includes face detection of a person, color detection of a subject, and the like.For example, during continuous shooting, it is possible to feed back this information at the next focus detection so that the same subject can be focused. is there.

In the exposure calculation process, for example, the metering value of each of the 35 divided metering areas is calculated from the first metering information, and each metering area is calculated based on the subject detection information and the information of the focusing target area determined in step S104. Calculate the weighting factor of. Then, the subject brightness is calculated by a well-known method such as weighting and averaging the photometric values for each photometric area. Once the subject brightness is calculated, exposure conditions such as shutter speed, aperture value, and shooting sensitivity that enable appropriate shooting for that brightness are determined.

In step S107, the microcomputer 41 calculates the light amount change characteristic of the photometric object based on the second photometric information. In the following, calculating the light intensity change characteristic of the photometric object will be referred to as flicker detection. The details of the flicker detection process executed in step S107 will be described later.

In step S108, the microcomputer 41 waits for the release switch 49 to be turned on. If it is not turned on, the process proceeds to step S101, and if the release switch 49 is turned on, the process proceeds to step S109.

In step S109, the microcomputer 41 instructs the flash microcomputer 61 to perform preliminary light emission of the flash 3. According to the instruction from the microcomputer 41, the flash microcomputer 61 causes the xenon tube 34 to emit light by a predetermined preliminary emission amount based on the output signal of the monitor sensor 37. In order to obtain the light measurement information (light measurement information at the time of preliminary light emission) of the subject during the preliminary light emission, the microcomputer 41 controls the timing generator 42 to perform predetermined accumulation control and signal reading control by the light measurement sensor 26. Do. When the signal storage of the photometric sensor 26 is completed, the microcomputer 41 reads out the signal stored in the photometric sensor 26, performs A / D conversion, and stores the signal in the RAM. The microcomputer 41 performs an operation of determining the main light emission amount of the flash 3 by a well-known method based on the stored signal information of the photometric sensor 26 stored in the RAM.

In step S110, the microcomputer 41 outputs a control signal to the first motor driver 47, drives the first motor 48, and flips up the main mirror 13 and the first reflection mirror 14. Subsequently, the microcomputer 41 outputs the aperture value information calculated in step S106 to the lens microcomputer 51. According to this information, the lens microcomputer 51 outputs a signal to the third motor driver 54 so as to drive the aperture 31, and drives the third motor 55.

In step S111, the microcomputer 41 adjusts the exposure timing when flicker is detected by the flicker detection in step S107 (the amount of light to be measured changes in a predetermined cycle). In the exposure timing adjustment, the flicker light source is used so that exposure unevenness and color unevenness do not occur in the image due to the influence of the change in the amount of light of the flicker light source, and exposure and color temperature do not vary among multiple images taken continuously. The exposure timing is adjusted to a predetermined phase in the change in the amount of light. For example, the degree of change in the amount of light is the smallest in the vicinity of the peak phase of the change in the amount of light in the flicker light source. Therefore, in the present embodiment, the exposure timing is adjusted to the peak timing in the change in the amount of light of the flicker light source. As a method of adjusting the exposure timing to the peak timing of the change in the amount of light of the flicker light source, for example, a known method such as the method described in Japanese Patent Application Laid-Open No. 2015-210283 may be used, and detailed description thereof will be omitted.

In step S112, the microcomputer 41 outputs a signal to the shutter driving means 50 to open the mechanical shutter 10. As a result, the light transmitted through the interchangeable lens 2 is incident on the image sensor 12 (exposure state). The microcomputer 41 refers to the signal processing circuit 43 so that the image sensor 12 is set to the storage time according to the shutter speed calculated in step S106 and the read gain according to the predetermined image sensitivity, and the signal is stored. Give instructions. Further, a flash 3 main flash instruction is output to the flash microcomputer 61 so that the flash 3 fires in synchronization with the exposure timing in order to take a flash image. The flash microcomputer 61 causes the xenon tube 34 to emit light based on the output signal of the monitor sensor 37 so as to have a light emission amount corresponding to the main light emission amount calculated in step S109 according to the main light emission instruction from the microcomputer 41. As described above, the imaging accompanied by the light emission of the flash 3 is executed.

When the accumulation time corresponding to the shutter speed calculated in step S106 elapses, the microcomputer 41 outputs a signal to the shutter driving means 50 and puts the mechanical shutter 10 in a light-shielding state. As a result, the light transmitted through the interchangeable lens 2 with respect to the image sensor 12 is blocked.

In step S113, the microcomputer 41 outputs information to the lens microcomputer 51 so as to open the aperture 31. According to the information from the microcomputer 4, the lens microcomputer 51 outputs a signal to the third motor driver 54 so as to drive the aperture 31, and drives the third motor 55. Further, the microcomputer 41 outputs a control signal to the first motor driver 47 to drive the first motor 48 to bring down the main mirror 13 and the first reflection mirror 14.

In step S114, the microcomputer 41 reads out the captured image information from the image pickup element 12 while performing A / D conversion, and issues an instruction to the signal processing circuit 43 to perform necessary correction processing and interpolation processing.

In step S115, the microcomputer 41 issues an instruction to the signal processing circuit 43 to adjust the white balance with respect to the captured image information. Specifically, the image based on the captured image information is divided into a plurality of regions, and the white region of the subject is extracted from the color difference signal for each region. Further, the gain of the red channel and the blue channel of the entire image is corrected based on the signal of the extracted region, and the white balance is adjusted.

In step S116, the microcomputer 41 issues an instruction to the signal processing circuit 43 to compress and convert the captured image information for which the white balance has been adjusted into a recording file format and store it in the storage means 46. The above is a series of operations related to luminescence photography.

Next, the operation related to the flicker detection process in step S107 will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram showing an operation related to the flicker detection process, and FIG. 7 is a diagram showing the weighting of each photometric area when calculating the subject brightness value for flicker detection according to the shooting environment.

In step S151, the microcomputer 41 recalculates after the subject in the focus target area is in focus in step S104, based on the focus state of each focus detection position in the imaging region, and the main subject area and the main subject area. The background area that can be regarded as being farther from the subject is discriminated. The main subject area is an area corresponding to the subject in the focusing target area, and the detection result of the subject detection process in step S106 may be added to the determination of the main subject area.

In step S152, the microcomputer 41 determines, based on the subject brightness value calculated in step S106, whether or not the subject brightness is such that it can be regarded as shooting in a high brightness environment such as outdoors during the daytime. Specifically, for example, it is determined whether or not the subject luminance value calculated in step S106 is equal to or greater than a preset first threshold value. The determination may be made based on the subject luminance value calculated in step S106 and the exposure condition determined in step S106. If the subject luminance value is less than the first threshold value, the process proceeds to step S153, and if the subject luminance value is equal to or greater than the first threshold value, the process proceeds to step S156.

In step S153, the microcomputer 41 determines, based on the subject brightness value calculated in step S106, whether or not the subject brightness is such that it can be regarded as shooting in a relatively bright indoor or other medium-luminance environment. Specifically, for example, it is determined whether or not the subject luminance value calculated in step S106 is equal to or greater than a preset second threshold value. The second threshold value is smaller than the first threshold value. The determination may be made based on the subject luminance value calculated in step S106 and the exposure condition determined in step S106. If the subject luminance value is less than the second threshold value, the process proceeds to step S154, and if the subject luminance value is equal to or greater than the second threshold value, the process proceeds to step S155.

When shifting to S154, it can be regarded as shooting in a low-brightness environment such as outdoors at night. When flash photography is performed in a low-brightness environment, as shown in FIG. 7A, the main subject to which the light of the flash 3 reaches is bright, and the background to which the light of the flash 3 does not reach becomes dark. In this way, when shooting with light emission in a low-brightness environment, even if the light source of the ambient light is a flicker light source, it has very little effect on the image, so the detection area for flicker detection is not distinguished between the main subject and the background. .. Therefore, in step S154, the microcomputer 41 equalizes the weighting of each of the 35 divided photometric areas as shown in FIG. 7B, and calculates the subject luminance value for flicker detection by simple averaging. Then, the subject brightness values for a plurality of flicker detections based on the plurality of second photometric information are compared, and the light amount change period of the photometric object is calculated. Further, the peak timing of the light amount in the change in the light amount of the photometric object is calculated from the change tendency of the subject brightness values for detecting a plurality of flickers. As a method for calculating the light intensity change cycle and the peak timing of the photometric object, for example, a known method such as the method described in Japanese Patent Application Laid-Open No. 2015-210283 may be used, and detailed description thereof will be omitted.

As shown in FIG. 7C, when flash photography is performed in a medium-brightness environment, the subject to which the light of the flash 3 reaches becomes brighter, which is the same as in a low-brightness environment. It becomes bright to some extent due to the ambient light. In such a medium-brightness environment, the ambient light also reaches the subject to which the flash 3 light reaches, but the ambient light reaches the subject less than the flash 3 light, so the ambient light source is a flicker light source. However, the effect on the subject is small. On the other hand, the background that the light of the flash 3 does not reach has a large influence when the light source of the ambient light is a flicker light source. Therefore, in step S155, the microcomputer 41 attaches importance to the background area at the time of flicker detection, and as shown in FIG. 7D, weights the photometric area of the background area more than the photometric area of the main subject area and performs weighted averaging. Calculates the subject brightness value for flicker detection. Since the method of calculating the peak timing of the amount of light in the change of the amount of light to be measured is the same as in step S154, the description thereof will be omitted.

When flash photography is performed in a high-brightness environment, the subject to which the light of the flash 3 reaches becomes bright as shown in FIG. 7 (e), which is the same as in a low-brightness environment or a medium-brightness environment, but the light of the flash 3 is emitted. Even the background that cannot be reached becomes uniform brightness due to the ambient light. In such a high-brightness environment, the ambient light also reaches the subject to which the light of the flash 3 reaches, and the amount of the ambient light reaches the subject is larger than that of the light of the flash 3. Therefore, if the light source of the ambient light is a flicker light source, the light of the flash 3 has a great influence on the subject to which the light reaches. If the light source of the ambient light is a flicker light source, the background that the light of the flash 3 does not reach is further affected because more ambient light reaches than the medium-luminance environment. However, what the photographer wants to take clearly is the main subject rather than the background. Therefore, in step S156, the microcomputer 41 attaches importance to the main subject area at the time of flicker detection, makes the photometric area of the main subject area larger than the weighting of the photometric area of the background area, and weights the average. Then, the subject brightness value for flicker detection is calculated. Since the method of calculating the peak timing of the amount of light in the change of the amount of light to be measured is the same as in step S154, the description thereof will be omitted.

As described above, by setting the weighting for each photometric area when calculating the subject brightness value for flicker detection according to the shooting environment, the light intensity change characteristic of the light from the photometric target can be accurately adjusted according to the shooting environment. Can be calculated. Although an example of setting the weighting for each photometric area according to the shooting environment has been described with reference to FIG. 7, the weighting value is not limited to the value shown in FIG. For example, the weighting value of the region in which the weighting value is “1” in FIGS. 7 (d) and 7 (f) may be set to “0”. Setting the weighting value to "0" means that the photometric value of the photometric area is not used when calculating the subject luminance value for flicker detection. That is, setting the weighting for each photometric area when calculating the subject luminance value for flicker detection also includes selecting the photometric area used when calculating the subject luminance value for flicker detection.

(Second Embodiment)
In the first embodiment, an example of discriminating between the main subject area and the background area using the focus state information has been described in order to set the weighting for each photometric area when calculating the subject luminance value for flicker detection. .. In the second embodiment, an example of discriminating between the main subject area and the background area by a method different from the method using the focus state information will be described. Since the imaging system of the present embodiment is the same as the imaging system of the first embodiment, detailed description thereof will be omitted.

The operation related to luminescence photography of the imaging system of the present embodiment will be described with reference to FIG. FIG. 8 is a diagram showing an operation related to light emission photographing of the imaging system of the present embodiment, and when the power switch (not shown) of the camera body 1 is turned on and the microcomputer 41 can operate, the operation shown in FIG. 8 starts. Will be done.

Since steps S201 to S206 are the same as steps S101 to S106 of FIG. 5, description thereof will be omitted.

After performing the subject detection process and the exposure calculation process in step S206, the microcomputer 41 waits for the release switch 49 to be turned on in step S207. Since steps S207 to S209 are the same as steps S108 to S110 of FIG. 5, description thereof will be omitted.

After that, in step S210, the microcomputer 41 performs the flicker detection process. The details of the flicker detection process executed in step S210 will be described later.

Since steps S211 to S216 are the same as steps S111 to S116 of FIG. 5, the description thereof will be omitted.

Next, the operation related to the flicker detection process in step S210 will be described with reference to FIG. FIG. 9 is a diagram showing an operation related to the flicker detection process, and step S251 is different from step S151 of FIG. 6 as compared with FIG.

In step S251, the microcomputer 41 determines the main subject area and the background area based on the photometric information of the subject during the preliminary light emission obtained in step S208. For example, based on the subject's metering information while the preliminary emission is being performed, the area where the metering value exceeds a predetermined value in each metering area is determined to be the area where the preliminary emission has arrived, and is used as the main subject area, and other areas. The area is used as the background area. Here, by using the difference between the photometric information of the subject during the preliminary light emission and the photometric information of the subject when the preliminary light emission is not performed, the reflected light component of the preliminary light emission can be extracted, so that the preliminary light emission can be extracted. The photometric information of the subject may be acquired immediately before or after.

Subsequent steps S252 to S256 are the same as steps S152 to S156 of FIG. 5, and thus the description thereof will be omitted.

As described above, in the present embodiment, since the main subject area and the background area are discriminated based on the photometric information of the subject while the preliminary light emission is being performed, the main subject area and the background area are mainly determined even for the area where the focal state cannot be obtained. The subject area and the background area can be discriminated.

Further, since the pre-emission is actually performed and the region brightened by the pre-emission is set as the main subject, the main subject region and the background region can be discriminated regardless of the accuracy of the information regarding the focal state.

(Third Embodiment)
In this embodiment, the method of setting the weighting for each photometric area when calculating the subject luminance value for flicker detection is different from that of the first embodiment and the second embodiment. Since the imaging system of the present embodiment is the same as the imaging system of the first embodiment, detailed description thereof will be omitted. Further, the operation related to the light emission photography of the imaging system of the present embodiment differs from that of the second embodiment only in the method of setting the weighting for each photometric area when calculating the subject luminance value for flicker detection, and the flicker detection process. The description other than the operation related to is omitted.

The operation related to the flicker detection process of the present embodiment will be described with reference to FIG. FIG. 10 is a diagram showing an operation related to the flicker detection process, and a step (step S352) for calculating the ambient light contribution rate as compared with FIG. 9 is added.

In step S351, the microcomputer 41 determines the main subject area and the background area based on the photometric information of the subject during the preliminary light emission obtained in step S208.

In step S352, the microcomputer 41 subtracts the subject brightness value calculated in step S206 from the subject brightness value obtained from the exposure conditions (shutter speed, aperture value, shooting sensitivity) at the time of shooting determined in step S206, and the ambient light. Determine the contribution rate.

If the result of subtracting the subject brightness value calculated in step S206 from the subject brightness value obtained from the exposure conditions at the time of shooting (subtraction result) is small, even if the flash 3 is not fired and only ambient light is used for shooting. The main subject will be photographed with almost appropriate brightness. For example, a case where the flash 3 is fired in order to put a catch light in the eyes of a person who is the main subject in a bright shooting environment outdoors in the daytime is applicable. In the present embodiment, if the subtraction result is less than the first threshold value, the scene has a large environmental light contribution rate.

On the other hand, when the subtraction result is large, the main subject is photographed darkly when the image is taken only with ambient light without firing the flash 3. In the present embodiment, if the subtraction result is greater than or equal to the second threshold value than the first threshold value, the scene has a small ambient light contribution rate, and if the subtraction result is greater than or equal to the first threshold value and less than the second threshold value, the environment is defined. The scene is in the light contribution rate. In addition, instead of classifying the ambient light contribution rate as described above, it may be obtained as a specific value. For example, if the reciprocal of the subtraction result is defined as the ambient light contribution rate, the ambient light contribution rate can be a specific value, and the ambient light contribution rate thus obtained may be compared with the threshold value.

In step S353, the microcomputer 41 determines whether or not the ambient light contribution rate is large, and if the ambient light contribution rate is not large, the process proceeds to step S354, and if the ambient light contribution rate is large, the process proceeds to step S357.

In step S354, the microcomputer 41 determines whether or not the ambient light contribution rate is medium, and if the ambient light contribution rate is not medium, the process proceeds to step S355, and if the environmental light contribution rate is medium, the process proceeds to step S356.

Since steps S355 to S357 are the same as steps S154 to S156 of FIG. 5, the description thereof will be omitted.

As described above, in the present embodiment, by changing the weighting for each photometric area when calculating the subject luminance value for flicker detection according to the ambient light contribution rate, each of them is affected by the flicker light source. The weighting for the metering area can be changed. Therefore, it is possible to accurately calculate the light amount change characteristic of the light from the photometric object according to the environment.

In the present embodiment, the main subject area and the background area are discriminated by the same method as in the second embodiment, but the main subject area and the background area are discriminated by the same method as in the first embodiment. You may.

Further, in the above three embodiments, an example in which the weighting for each photometric area when calculating the subject luminance value for flicker detection is changed by three patterns has been described, but it depends on the subject luminance and the ambient light contribution rate. It may be changed in four or more patterns. Alternatively, one of two of the three patterns (for example, simple average and background-oriented, background-oriented and main subject-oriented, etc.) may be selected according to the subject brightness and the ambient light contribution rate.

Further, in the above three embodiments, the image pickup system in which the illumination device is attached to the image pickup device has been described as an example, but the image pickup device may include the illumination device.

Further, in the above three embodiments, the light amount change characteristic of the photometric object is calculated based on the photometric information obtained by using the photometric sensor 26, but it is based on the photometric information obtained by driving the image sensor 12. The light amount change characteristic of the photometric object may be calculated. The photometric information obtained by driving the image sensor 12 may also be used in the calculation of the subject luminance value and the determination of the ambient light contribution rate.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

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

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

1 Camera body 2 Interchangeable lens 3 Flash 20 Focus detection sensor 26 Photometric sensor 41 Microcomputer 51 Lens microcomputer 61 Flash microcomputer

Claims (5)

A photometric means for obtaining the photometric values of each of the plurality of photometric areas divided into the main subject area and the other areas in the imaging area.
A determination means for comparing the brightness value of the subject and the threshold value based on the photometric result of the photometric means, and
Based on the determination result of the determination means, the setting means for setting the weighting degree corresponding to the plurality of measurement areas when detecting the flicker, and the setting means.
It has a detecting means for detecting flicker based on a metering value of each of the plurality of metering areas and a weighting degree set by the setting means.
When the determination means determines that the brightness value of the subject is smaller than the first threshold value, the setting means sets the weighting degree corresponding to the plurality of photometric areas to be substantially the same, and the brightness value of the subject. The imaging apparatus is characterized in that when it is determined that is equal to or greater than a second threshold value larger than the first threshold value, the weighting degree of the main subject region is larger than that of the other regions. When the setting means determines that the brightness value of the subject is equal to or higher than the first threshold value and smaller than the second threshold value, the weighting degree is larger in the other regions than in the main subject region. The imaging apparatus according to claim 1, wherein the image pickup apparatus is used. It said plurality of light metering areas on the basis of the focus state of each focus detection position of the imaging area, an imaging apparatus according to claim 1 or 2, characterized in that it is divided into the main object area and background area .. The imaging device according to any one of claims 1 to 3, wherein the detecting means detects flicker based on a light amount change characteristic of a subject calculated based on a photometric result of the photometric means. A metering step for obtaining the metering values of each of the plurality of metering areas divided into the main subject area and the other areas in the imaging area.
A determining step of comparing the luminance value and the threshold value of the subject based on the photometry result of the photometry step,
Based on the determination result of the determination step, a setting step for setting the weighting degree corresponding to the plurality of measurement areas when detecting flicker, and a setting step.
It has a detection step for detecting flicker based on the measurement value of each of the plurality of measurement areas and the weighting degree set in the setting step.
In the setting step, when it is determined in the determination step that the brightness value of the subject is smaller than the first threshold value, the weighting degrees corresponding to the plurality of photometric areas are substantially the same, and the brightness value of the subject is set to be substantially the same. Control of the image pickup apparatus, characterized in that, when it is determined that is greater than or equal to the second threshold value larger than the first threshold value, the weighting degree of the main subject region is larger than that of the other regions. Method.

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