JP2019008081A - Imaging device and camera system - Google Patents

Abstract

To provide an imaging device that enables light to be emitted with proper brightness upon rear curtain synchronization light emission picture-taking.SOLUTION: An imaging device has: a light emission device; a first image pick-up element; light emission-amount determination means that conducts pre-light emission prior to picture-taking, and determines an amount of light emission upon the picture-taking on the basis of pre-light emission information; rear curtain synchronization control means that controls light emission in synchronization with rear curtain travelling; light emission-amount correction means that corrects an amount of light emission upon the rear curtain light emission from the amount of light emission determined by the light emission-amount determination means; main subject identification means that identifies a main subject from inside a picture-taking area; and distance distribution information generation means that acquires distance distribution information on the picture-taking area. The main subject identification means is configured to: identify a main subject position upon synchronization light emission from the distance distribution information periodically generated during exposure of the first image pick-up element; and correct an amount of light emission upon the synchronization light emission from main subject position information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus and a camera system, and more particularly to control of a strobe.

  Conventionally, cameras can take clear pictures even in dark places such as at night by using a built-in strobe or a separate strobe as auxiliary light for shooting in a dark place. .

  In such a conventional camera strobe, pre-flash is performed before the actual imaging at the time of release, and the difference between the luminance level of the subject and the appropriate dimming level is obtained from the pre-captured image, and the actual flash level is determined according to the difference. Imaging is performed by determining a light emission amount (main light emission amount) at the time of imaging.

  Patent Document 1 discloses a technique for detecting a face of a subject from an image at the time of pre-flash and calculating a main flash amount according to the detected face area. Patent Document 2 discloses a technique for correcting the main light emission amount from subject distance information at the time of pre-light emission and immediately before photographing.

Japanese Patent Laying-Open No. 2015-184508 JP 2003-66504 A

  However, in the prior art disclosed in the above-mentioned patent document, when the subject moves during exposure in the rear curtain sync flash photography, if the light is emitted with the main flash amount calculated based on the pre-flash, the positional relationship between the camera and the subject The light emission amount may not be appropriate due to the change of.

  As an example of shooting with rear-curtain sync flash, after exposing a light trail such as an LED light held by a person in the dark, the strobe is fired when the person takes a pose for shooting, and the exposure ends. You may shoot like this. In such a case, since the person moves in various directions in order to draw various light trajectories, the person moves during pre-light emission and main light emission, and the light emission amount may be inappropriate.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus capable of emitting light with appropriate brightness at the time of rear curtain sync flash photography.

In order to achieve the above object, an imaging apparatus according to the present invention includes:
A light emitting device;
A first image sensor;
A light emission amount determining means for performing pre-light emission before shooting and determining the light emission amount at the time of shooting based on the pre-flash information;
Rear curtain sync control means for controlling the light emission by synchronizing with the shutter running of the rear curtain;
A light emission amount correcting means for correcting the light emission amount in the rear curtain sync light emission from the light emission amount determined by the light emission amount determining means;
Main subject identification means for identifying the main subject from within the shooting area;
Having distance distribution information generating means for acquiring distance distribution information of the imaging region;
The main subject specifying means specifies a main subject position at the time of sync light emission from the distance distribution information periodically generated during exposure of the first image sensor, and emits light at the time of sync light emission from the main subject position information. It is characterized by correcting the amount.

  According to the present invention, it is possible to provide an imaging apparatus capable of emitting light with appropriate brightness at the time of rear curtain sync flash photography.

Sectional drawing of the camera, the interchangeable lens, and the strobe according to the first embodiment of the present invention 1 is a block diagram showing a schematic configuration of a camera body according to a first embodiment of the present invention. The flowchart which shows operation | movement of the camera of this invention. Flowchart of pre-emission / main emission amount calculation of the present invention Flowchart of main subject position specification of the present invention The figure for demonstrating the light emission correction amount based on the distance information of the main subject Table for calculating the amount of light emission correction based on the position of the main subject in the screen Conceptual diagram of main light emission amount correction of the present invention Conceptual diagram of main light emission amount correction of the present invention Conceptual diagram of main light emission amount correction of the present invention Conceptual diagram of main light emission amount correction of the present invention 1 is a timing chart showing the operation of the camera according to the first embodiment of the present invention. Sectional drawing of the camera, interchangeable lens, and strobe concerning the 2nd Embodiment of this invention The block diagram which shows schematic structure of the camera main body concerning the 2nd Embodiment of this invention. Timing chart showing the operation of the camera according to the second embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a camera, an interchangeable lens, and a strobe according to an embodiment of the present invention.

  The configuration of the camera according to the first embodiment of the present invention will be described below with reference to FIG. This figure shows the configuration of a camera with interchangeable lenses.

  In FIG. 1, 1 is a camera body, 2 is an interchangeable lens, and 3 is a detachable strobe. Reference numeral 315 denotes a lens mount contact portion for lens connection, and 314 denotes a connection portion to which a strobe is attached. The light flux from the subject incident through the photographing lens 2 forms an image on the image sensor 206, and the subject image is exposed.

  Reference numeral 209 denotes a distance sensor, for example, a sensor that acquires distance information using a TOF (Time Of Flight) method. In the TOF method, distance information is acquired by measuring a delay time from light projection onto a subject to reception of reflected light.

A display unit 210 displays captured still images, moving images, and the like. Reference numeral 316 denotes a shutter mechanism that controls exposure time and shields an optical image that has passed through the photographing lens 2.
Further, the present invention does not require a lens or strobe to be detachable, and can also be applied to a lens-fixed camera or a camera incorporating a strobe function.

  FIG. 2 is a block diagram showing a schematic configuration of the camera body.

  Connected to the camera microcomputer (CPU) 100 are a signal input circuit 204 for detecting a switch group 214 for various operations of the camera, and an image sensor (image sensor) 206 composed of a CMOS sensor, a CCD, or the like. Yes. In addition, a shutter control circuit 208 for controlling the shutter magnets 218a and 218b is connected. The photographic lens 2 controls the focal position and the aperture through the lens communication circuit 205 and the lens mount contact portion 315. Further, the flash unit 3 controls the light emission timing and the light emission amount through the flash communication circuit 205 and the flash connection unit 314.

  The operation of the camera is determined by the photographer operating the switch group 214. The switch group 214 includes a release button, a dial, and the like.

  The CPU 100 controls the image sensor 206 to detect the brightness of the subject and determines the aperture value and shutter speed of the taking lens 2. Further, the CPU 100 detects the focus state of the photographing lens by controlling the image sensor 206 and controls the photographing lens 2 so as to be in an appropriate focus state. Further, the CPU 100 controls the distance sensor 209 to acquire distance distribution information of the shooting area. Then, the aperture value of the photographing lens 300 is controlled via the lens communication circuit 205, the shutter speed is controlled by adjusting the energization time of the magnets 218a and 218b via the shutter control circuit 208, and the image sensor 206 is further controlled. The shooting operation is performed.

  The strobe flash shooting operation of the camera configured as described above will be described with reference to the flowchart shown in FIG. Here, it is assumed that the rear curtain sync flash mode is set by the photographer's setting operation. The trailing curtain sync light emission is a mode in which light is emitted immediately before the shutter starts to close during photographing. In many cases, the rear curtain sync shooting is performed in a low illumination environment. However, in this embodiment, since the distance distribution information is acquired by a TOF type distance sensor, the influence is small even if the ambient light intensity is low.

  In step S300, the CPU 100 monitors the state of the switch SW1 that is turned on when the release button is pushed down to the first stroke. If the switch SW1 is on, the process proceeds to step S301, and AF and AE operations are performed. The AF operation is an operation of adjusting the focus state by driving the lens by performing AF calculation for detecting the focus state of the photographing lens from the signal obtained from the image sensor 206. The AE operation is to calculate subject luminance from a signal obtained from the image sensor 206.

  Next, in step S302, the CPU 100 monitors the state of the switch SW2 that is turned on when the release button is pushed down to the second stroke. When the switch SW2 is turned on, the process proceeds to step S303, where the pre-light emission and the main light emission amount are detected. Perform the operation.

  FIG. 4 is a flowchart of pre-light emission and main light emission amount calculation.

  In step S <b> 400, the CPU 100 controls the image sensor 206 so as to accumulate a signal for photometry before pre-emission and to read a photometry signal. The signal accumulation for photometry before pre-flash is a signal accumulation process for controlling the accumulation of the image sensor 206 without causing the strobe to emit light and calculating the luminance value of the subject due to the external light that is not the strobe light.

  In step S <b> 401, the CPU 100 controls the image sensor 206 so as to accumulate the pre-emission reflected light photometric accumulation signal. The pre-emission reflected light metering accumulation is a signal accumulation process for calculating the luminance value of the subject by the reflected light of the strobe light by controlling the accumulation of the image sensor 206 by emitting the strobe light. At this time, the signal accumulated in the image sensor 206 is a mixture of strobe light emission reflected light and non-strobe light outside light.

  In step S402, the CPU 100 detects a human face position from the image acquired by the imaging sensor 206 in step S401.

  In step S <b> 403, the CPU 100 acquires distance distribution information of the imaging region from a signal obtained from the distance sensor 209.

  In step S404, the CPU 100 determines the number of faces detected in step S402. If the number is “0”, the process proceeds to step S405. If the number is “1”, the process proceeds to step S406. Advances the process to step S407.

  In step S <b> 405, the CPU 100 calculates the luminance in the area using the area that matches the AF area as the main subject area. The “AF area” is an AF area selected by the photographer or an AF area determined by the “AF / AE operation” in step S301.

  In S <b> 406, the CPU 100 calculates the luminance in the area by setting the area where the face is detected as the main subject area.

  In S407, based on the distance distribution information of the shooting area obtained in S403, the CPU 100 sets the area where the closest face is detected as the main subject area, and calculates the luminance in the area.

  In step S408, the CPU 100 calculates a strobe light emission amount (main light emission amount) at which the luminance in the main subject area at the time of shooting is appropriate. For example, if the image signal level of pre-imaging by pre-emission is an appropriate level, the same amount of light emission as that of pre-emission may be used. Processing such as setting the light emission amount to double is performed. Pre-emission reflected light from which external light that is not strobe light is removed is calculated from the difference between the signals obtained in steps S400 and S401, and a strobe light emission amount (main light emission amount) at the time of photographing is calculated.

  Returning to FIG. 3, in steps S <b> 304 and S <b> 305, the CPU 100 controls the shutter 316 and the image sensor 206 to perform the exposure operation of the image sensor 206.

  In step S306, the CPU 100 acquires distance distribution information of the imaging region from a signal obtained from the distance sensor 209.

  In step S307, the CPU 100 specifies the position of the main subject from the temporal change in the distance distribution information of the shooting area.

  FIG. 5 shows a flowchart for specifying the main subject position.

  In step S500, the CPU 100 calculates frame correlation information of the distance distribution information of the shooting area acquired immediately before and the distance distribution information of the shooting area acquired so far.

  In step S501, the CPU 100 specifies the position of the main subject from the frame correlation information calculated in step S500.

  In step S502, the CPU 100 determines whether or not the main subject has been out of frame from the shooting area. If the main subject position cannot be specified in step S501, it is determined that the frame is out of the shooting area. If the main subject is out of the frame from the shooting area, the CPU 100 advances the process to step S503. On the other hand, if the main subject is not out of the frame of the shooting area, the CPU 100 advances the process to step S504.

  In step S503, the CPU 100 determines whether or not another moving object exists in the screen in which the main subject is out of the shooting area. If there is no moving object, the CPU 100 advances the process to step S505 to set an area that matches the AF area as the main subject area. If there is a moving object, the CPU 100 advances the processing to step S506, and identifies the moving object having the closest distance among the detected moving objects as the main subject.

  In step S504, the CPU 100 determines whether there is a moving object other than the main subject. If there is a moving object, the CPU 100 advances the process to step S507, and identifies the main object up to that point and the detected moving object that is closer to the camera as the main object. By using the main subject as the main subject that is closer to the camera, it is possible to prevent overexposure due to light emission when a subject other than the original main subject enters the frame. If there is no moving object, the CPU 100 does not update the main subject and ends the main subject position specification.

  Returning to FIG. 3, in step S308, the CPU 100 determines whether or not the exposure time has elapsed. The predetermined time is determined according to the shutter speed set by the photographer. Steps S306, S307, and S308 are repeated until a predetermined time elapses, and the distance distribution information of the imaging region is periodically acquired to continue specifying the main subject position. By periodically specifying the main subject position, the position of the main subject can be specified with high accuracy. For example, as shown in FIG. 8B, a person is positioned in front of an obstacle during pre-flash and the person is identified as a main subject, and then the person moves and is positioned behind the obstacle during main flash. To do. At this time, since the image sensor 206 is under exposure, face detection using the image of the image sensor 206 is impossible. Further, when the distance distribution information is acquired only after the pre-light emission and immediately before the main light emission, it cannot be determined whether or not the object located at a short distance detected from the distance distribution information is a person. As described above, if the subject information is acquired only at the time of the main light emission, the movement of the person cannot be captured, and there is a possibility that the obstacle is erroneously recognized as the main subject. On the other hand, by periodically acquiring the distance distribution information of the shooting region and continuing to specify the main subject position, the movement of the main subject can be supplemented continuously, and erroneous recognition of the main subject can be prevented. it can. If it is determined in step S308 that the predetermined time has elapsed, the CPU 100 advances the process to step S309.

  In step S309, the CPU 100 corrects the main light emission amount determined in step S303 based on the main subject position specified by repeating steps S306 and S307. First, the main light emission amount is corrected based on the distance in the depth direction (Z1) between the camera and the main subject position acquired during pre-flash and the distance in the depth direction (Z2) between the camera and the main subject position when a predetermined time has elapsed. FIG. 6 shows the relationship between the distance ratio Z2 / Z1 in the depth direction and the light emission correction amount. For example, when the main subject moves away during main light emission and Z2 / Z1 = √2, the light reflected and arrived from the subject during main light emission is attenuated to ½. Therefore, the main light emission amount is corrected by a factor of two.

  Next, the main light emission amount is corrected based on the on-screen position (XY direction) of the subject at the time of pre-emission and the elapse of a predetermined time and the light distribution characteristics of the strobe. FIG. 7 is a table for correction based on the strobe light distribution characteristic.

  For example, when the position of the main subject on the screen at the time of pre-emission is (X, Y) = (− 3, −2), the value of the correction table is 2.5. On the other hand, when the position of the main subject on the screen when the predetermined time has elapsed is (X, Y) = (1, 0), the value of the correction table is 0.5. Therefore, the main light emission amount is corrected to ¼ (= 2 ^ (0.5−2.5)). The light distribution characteristic information of the strobe is generated for each strobe based on the strobe information acquired by communication between the camera and the strobe.

  The correction amount calculated from the distance between the camera and the subject position calculated as described above and the correction amount calculated from the on-screen position of the subject are combined, and the main flash amount at the time of rear curtain sync flash is calculated from the main flash amount calculated from the pre-flash amount. Correct the flash output. In the above-described example, the light emission amount that is 1/2 (= 2 × 1/4) from the main light emission amount calculated by the pre-light emission amount is set as the main light emission amount in the rear curtain sync light emission.

  FIGS. 8A to 8D show conceptual diagrams of main subject identification and light emission amount correction as described above. When the main subject approaches the camera, the light emission amount is reduced, and when the main subject moves away from the camera, the light emission amount is increased. When the main subject moves to the center of the screen, the light emission amount is reduced, and when the main subject moves to the peripheral area of the screen, the light emission amount is increased. The light emission amount may be corrected by predicting the subject position at the main light emission timing from the continuously acquired distance information distribution history.

  In step 310, the CPU 100 controls a strobe for photographing and performs main light emission control for photographing.

  In step 311, the CPU 100 ends the exposure of the image sensor 206, closes the shutter, and ends the shooting operation.

  FIG. 9 shows a timing chart of the operation described above.

  The distance sensor 209 continues to acquire the distance distribution information history from the pre-light emission to the main light emission, and continues to specify the main subject position during the exposure of the image sensor 206.

  As described above, according to the first embodiment of the present invention, during the second curtain synchronization, during the exposure of the image sensor, the distance distribution information of both photographing devices is acquired from the distance sensor, and the main subject position is specified. Based on the main subject position information, the main light emission amount determined by the pre-light emission is corrected. As a result, even if the subject moves during the exposure of the image sensor, the strobe can be emitted with an appropriate amount of light emission, and a good image can be taken.

  In the present embodiment, the photographer sets the shutter speed in advance, but it is also effective in the bulb photography mode. Even if the photographer releases the release button at an arbitrary timing, the subject position can always be specified, so that the main light emission amount can be corrected based on the subject position at the timing.

  A camera according to the second embodiment of the present invention will be described below with reference to FIGS.

  FIG. 10 is a cross-sectional view of a camera, an interchangeable lens, and a strobe according to the second embodiment, and FIG. 11 is a block diagram illustrating a schematic configuration of a camera body according to the second embodiment. In FIG. 10 and FIG. 11, the description of what overlaps with FIG. 1 is omitted.

  Reference numeral 305 denotes a half mirror that splits an optical image passing through the photographing lens 2 and guides it to the image sensor 206 and the image sensor 207.

  The image sensor 207 is a second image sensor for capturing an optical image of a subject imaged by the photographing lens 2 as an image signal. The imaging sensor 207 is mainly intended to capture moving images and LV (live view), and can periodically acquire images even when the imaging sensor 206 is under exposure. In addition, pixels for focus detection are arranged in the image sensor 207, and it is possible to acquire the defocus state of the lens and the distance distribution information of the imaging region using the signal of the image sensor 207.

  FIG. 12 is a timing chart in the second embodiment.

  The imaging sensor 207 periodically repeats imaging (for example, 30 fps) and continues to acquire an image for LV. For this reason, in the second embodiment, even when the image sensor 206 is under exposure, the second image sensor 207 can acquire the image of the shooting area and can detect the face of the shooting area.

  As described above, according to the second embodiment of the present invention, face position information can be used for specifying the main subject position in the “specifying main subject position” in step S307 in FIG. Specific accuracy can be increased. In the first embodiment, since it is a distance sensor, it cannot be determined whether or not the moving object is a person, and even a person other than a person is identified as a main subject. On the other hand, in the second embodiment, since a face can be detected, it is possible to specify a person as a main subject with priority.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1 camera, 2 interchangeable lens, 3 strobe, 100 CPU,
206 Image sensor, 209 Distance sensor, 316 Shutter

Claims (8)

A light emitting device (3);
A first image sensor (206);
(100) a light emission amount determining means for performing pre-light emission before shooting and determining a light emission amount at the time of shooting based on the pre-flash information;
(100) rear curtain sync control means for controlling the light emission by synchronizing with the shutter running of the rear curtain;
A light emission amount correcting means for correcting the light emission amount at the time of rear curtain sync light emission from the light emission amount determined by the light emission amount determining means; (100, S309)
Main subject specifying means for specifying the main subject from within the imaging region; (100, 206, 209, 207)
Distance distribution information generating means for acquiring distance distribution information of the imaging region; (209, 207)
The main subject specifying means specifies a main subject position at the time of sync light emission from the distance distribution information periodically generated during exposure of the first image sensor, and (S306, S307, S308).
An image pickup apparatus that corrects a light emission amount during synchronized light emission from main subject position information (S309). The imaging apparatus according to claim 1, wherein the main subject specifying unit specifies a main subject from a frame correlation of the distance distribution information generated periodically. 2. The main subject specifying unit, when a subject different from the main subject specified at the time of pre-light emission is detected, specifies the main subject as the one closer to the imaging device. 2. The imaging device according to 2. 4. The main subject position information is a distance between the imaging device and the main subject, and the light emission amount at the time of sync light emission is corrected based on the distance. Imaging device. The main subject position information is a position of a main subject in a screen, and a light emission amount during sync light emission is corrected based on a position of the main subject and a light distribution characteristic of the strobe. Item 5. The imaging device according to any one of Items 4 to 4. The distance distribution information includes a light projecting unit that projects distance measuring light and a distance measuring sensor (209) that receives the distance measuring light that is reflected back to the subject and receives a signal mainly from the distance measuring sensor. The imaging apparatus according to any one of claims 1 to 5, wherein the imaging device is acquired. 6. The image sensor according to claim 1, further comprising a second image sensor (207) having focus detection pixels, wherein the distance distribution information is acquired from a signal acquired from the second image sensor. The imaging device according to any one of the above. It has face detection means (S402), acquires face information from an image obtained from the second image sensor, and the main subject specifying means specifies a main subject based on the face information. The imaging device according to claim 7.