JP2018101081A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a file size of a recorded image and improve a reading speed of two image pickup elements for acquiring an image signal for display or recording and detecting a focus. SOLUTION: A light flux passing through a photographing lens is divided into a plurality of light fluxes by a light flux dividing means, one of the plurality of light fluxes is received by a first image pickup element, and the other light flux is received by a second image pickup element. The first and second image pickup devices each have a plurality of pixel units, and each pixel unit has a pair of photoelectric conversion units. The read mode of the pixel signal of the first image sensor and its range are determined according to the result of performing focus detection using the signal acquired by the second image sensor and acquiring the focus information. The read mode is the first and second of the first output signal obtained by independently reading the signals of the plurality of photoelectric conversion units and the second output signal read by adding the signals of the plurality of photoelectric conversion units. It is either a first read mode for reading both of the output signals of the above and a second read mode for reading only the second output signal. [Selection diagram] Fig. 1

Description

  The present invention relates to an imaging device, and more particularly to an imaging device capable of pupil-division focus detection.

  In recent years, multi-functionalization of solid-state imaging devices used in imaging devices such as digital still cameras and digital video cameras has been advanced. In the imaging device of Patent Document 1, a technique capable of pupil-focusing focus detection is disclosed for an imaging device. In this technique, one pixel of an image sensor has two photodiodes, and each photodiode is configured to receive light that has passed through different pupils of a photographing lens by one microlens. Therefore, the phase difference can be detected by comparing the output signals from the two photodiodes.

  Also, by adding the output signals from the two photodiodes, a normal captured image signal can be obtained. In order to perform focus detection using an imaging device in which two photodiodes are provided in one pixel, it is necessary to acquire signals from the two photodiodes. Therefore, when trying to obtain a focus detection signal in the entire range of the pixel region, the amount of signal to be read is doubled compared to a conventional imaging device in which one pixel has only one photodiode, and the readout time is increased. It will increase significantly.

JP 2014-89260 A

  In Patent Document 1, the readout range of the pixel signal and the addition signal and the thinning rate within the range are changed depending on the shooting conditions. However, since the thinning is performed in units of lines, the reduction of the readout time is limited.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus capable of suppressing the file size of a recorded image and improving the reading speed.

  In order to achieve the above object, the present invention includes a first imaging device that has a light beam splitting unit that splits a light beam that has passed through a photographing lens into a plurality of light beams, and that receives one of the divided light beams, In an imaging apparatus having a second imaging element that receives a light beam, each of the first and second imaging elements having a plurality of pixel units, and each pixel unit having a pair of photoelectric conversion units per pixel unit The focus detection is performed using the signal acquired by the second image sensor, the focus information is acquired, and the readout mode and the range of the pixel signal of the first image sensor are determined according to the result of the focus information. And a reading mode in which the first signal output obtained by independently reading the signals of the plurality of photoelectric conversion units and the second output signal read by adding the signals of the plurality of photoelectric conversion units are read. Of which, both the first signal output and the second signal output And wherein the read and the first read mode, which is either the second read mode for reading only the second signal output.

  According to the present invention, it is possible to provide an imaging apparatus capable of suppressing the file size of a recorded image and improving the reading speed.

The figure which shows the flowchart of imaging | photography operation | movement of the imaging device which concerns on 1st Example of this invention. 1 is a schematic diagram of an interchangeable lens camera according to a first embodiment of the present invention. The figure which shows notionally the light beam when the light beam emitted from the exit pupil of the photographing lens enters the unit pixel The figure explaining the read-out mode according to the captured image which concerns on 1st Example of this invention. Schematic diagram of an interchangeable lens camera according to a second embodiment of the present invention The figure which shows the flowchart of imaging | photography operation | movement of the imaging device which concerns on 2nd Example of this invention. The figure which displayed the divided area of the image pick-up elements 102 and 607 based on 2nd Example of this invention in piles.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[Example 1]
FIG. 2 is a schematic diagram of the interchangeable lens camera body 100 according to the first embodiment of the present invention. The interchangeable lens 200 has a lens group and is defined as a photographing lens 201 here. Further, a lens having a focus function among the photographing lenses is defined as a focus lens 210 (not shown).

  The light beam that has passed through the photographing lens 201 of the interchangeable lens 200 is incident on the main mirror 101 in a mirror unit (not shown) provided in the camera body 100. The main mirror 101 which is a light beam splitting unit is a half mirror in this embodiment, but may not be a half mirror as long as it can split a light beam. As the half mirror, for example, a pellicle mirror is used. However, the half mirror is not limited thereto, and a half mirror configured using a glass plate or the like may be used.

  The pellicle mirror is configured, for example, by coating a thin transflective film such as polyethylene terephthalate (PET) so that desired transmittance and reflectance can be obtained. The transmittance and reflectance of the half mirror are not limited to 50% and 50%, respectively, and may be other values.

  One of the light beams divided by the main mirror 101 passes through the main mirror 101 and is guided to the first image sensor 102. The other of the light beams divided by the main mirror 101 is reflected by the main mirror 101 and guided to the second image sensor 103.

  The first image sensor 102 and the second image sensor 103 made of CMOS area sensors have pixel portions arranged in a matrix that converts a subject image into an electrical signal. The plurality of pixel portions 102a and 103a included in each of the first image sensor 102 and the second image sensor 103 can acquire both a focus detection signal and an image signal for recording or display. The structure of the pixel portion will be described later. The image signal converted into the electrical signal is subjected to image processing, correction processing, and conversion processing into a recorded image by the camera CPU 107.

  The display image and various setting states of the camera main body 100 are displayed on the external display unit 109 which is an external monitor configured by an LCD (liquid crystal display) or a finder internal display unit 106 described later. The finder unit 104 is configured by combining an eyepiece unit 105 and a finder internal display unit 106.

  The finder internal display unit 106 displays the display image converted by the first image sensor 102 on the screen, thereby performing finder display (EVF). At the time of shooting, imaging information processed by a correction processing unit 107a (not shown) including an image correction processing unit inside the camera CPU 107 is recorded in a recording device 108 including an internal memory or an external memory card.

  In the present embodiment, since the subject image is picked up by the first image pickup device 102 and recorded, an image pickup device with a larger number of pixels, high density and high accuracy is required. On the other hand, since the second image sensor 103 is mainly used for focus detection of the in-focus position, the number of pixels is not as large as that of the first image sensor 102. Therefore, the size of the entire image sensor is substantially the same for the first image sensor 102 and the second image sensor 103, but the light receiving area per pixel is larger than that of the first image sensor 102. . Therefore, the second image sensor 103 has a lower pixel density, and the number of pixels per unit area is smaller than that of the first image sensor 102.

  Then, the data amount of the image signal imaged by the second image sensor 103 is reduced, and the processing time for calculating the focus evaluation value is further reduced. Thereby, the maximum detection time of the focus evaluation value is shortened. Further, by performing focus detection with only one image sensor, it is not necessary to drive for focus detection of one image sensor depending on the brightness of the subject and the degree of defocus, so that power consumption can be suppressed.

  Based on the defocus amount, the camera CPU 107 calculates a lens driving amount for moving the photographing lens 201 to a position where the photographing lens 201 is brought into focus. The lens driving amount is transmitted to the lens CPU 203 through the lens communication unit 204. However, the lens CPU 203 may calculate the lens driving amount based on the defocus amount obtained by the focus detection calculation unit 107b.

  In this case, the lens CPU 203 receives the defocus amount from the camera CPU 107. The lens CPU 203 controls the actuator 202 to drive the focus lens 210 to adjust the focus.

[Pixel structure]
The structure of a plurality of pixel portions included in the first and second imaging elements 102 and 103 will be described with reference to FIG. FIG. 3 is a diagram conceptually showing a light beam when a light beam emitted from the exit pupil of the photographing lens enters the unit pixel. In the figure, reference numeral 300 denotes a unit pixel, which includes a first photodiode 301A and a second photodiode 301B. Reference numeral 302 denotes a color filter, 303 denotes a microlens, and 304 denotes an exit pupil of the photographing lens.

  Assuming that the optical axis 305 is the center of the light beam emitted from the exit pupil with respect to the unit pixel having the micro lens 303, the light passing through the exit pupil enters the unit pixel 300 with the optical axis 305 as the center. As shown in FIG. 3, when 306 and 307 are partial regions of the exit pupil of the photographing lens, the light beam passing through the pupil region 306 is received by the photodiode 301A through the microlens 303.

  Similarly, the light beam passing through the pupil region 307 is received by the photodiode 301 </ b> B through the microlens 303. Accordingly, each of the photodiodes 301A and 301B receives light from different areas of the exit pupil of the photographing lens, and the phase difference can be detected by comparing the signals of the photodiodes 301A and 301B. Here, the signal obtained from the photodiode 301A is defined as an A image (first image), the signal obtained from the photodiode 301B is defined as a B image (second image), and the addition of adding the A image and the B image together. If the signal is an A + B image, this A + B image can be used as a captured image.

  Next, the distance distribution of the subject is calculated by a known means from the acquired A and B images by distance calculation processing. For example, a part of a pair of AB images is cut out, an image shift amount is obtained by correlation calculation in the cut out window, and the baseline length is calculated from the interval between the center of gravity of the pupil region 306 transmittance distribution and the center of gravity of the transmittance distribution of the pupil region 307. Ask for. The distance can be calculated by obtaining the defocus amount from the obtained image shift amount and the base line length. If the correlation calculation is performed while shifting the window, the distance distribution of the subject can be acquired.

  Subsequently, the refocus plane and the amount of blur to be added are set. At this time, the acquired image and the obtained distance distribution may be displayed on the display unit, and the photographer (user) may manually set the refocus plane and the amount of blur. The imaging apparatus 100 may automatically set the refocus plane and the amount of blur from the acquired image and the acquired distance distribution. For example, it is possible to determine a main subject with respect to the acquired image using a known face recognition technique and set a refocus plane in accordance with the main subject.

[Operation in shooting mode]
FIG. 1 is a diagram illustrating a flowchart of a shooting operation of the imaging apparatus according to the present embodiment. This operation starts when the user operates an operation member (not shown) of the camera 100 to turn on the power switch and set the shooting mode by the shooting mode selector. In the present embodiment, the person photographing mode is described, but the present embodiment can also be implemented in other photographing modes.

  In step S401, it is determined whether the person photographing mode is selected by the mode selector of the operation member. In the portrait shooting mode, there are a method in which the camera recognizes the main subject, a method in accordance with the user's manual setting operation, and a method in which the camera automatically recognizes. Here, the description is continued assuming that the camera adopts a method of automatically recognizing the main subject.

  If the person photographing mode is set in step S401, the process proceeds to step S402, and the focus state of the photographing lens 200 is detected using the second image sensor 103. From the focus detection result in step S402, the defocus amount of the photographing lens 200 is calculated in step S403, and the driving amount of the photographing lens 200 is determined based on the defocus amount. In step S404, the actuator 202 as an adjusting unit drives the focus lens 210 based on the lens driving amount. In step S405, the face of the person and its position are detected using a known face recognition technique.

  Next, the process proceeds to step S406, in which the face reading mode is set in step S407 when the face is detected, and in step S417 when the face is not detected, respectively. In step S408, imaging is performed using the first imaging element 102 in accordance with the readout mode in each pixel.

  Here, a signal reading mode will be described with reference to FIG. FIG. 4A is a diagram in which the light receiving areas of the first and second imaging elements 102 and 103 of the imaging apparatus of this embodiment are divided into 64 areas of 8 × 8. Each divided area is referred to as a divided area 501, and a divided area corresponding to the upper left of the screen is set as d00, respectively, as shown in FIG. 4A, d00 to d77.

  Here, it is assumed that the second image sensor 103 has substantially the same light receiving area as the first image sensor 102 and has a smaller number of pixels than the first image sensor 102. In addition, the positions of the subjects in the divided areas correspond to the first image sensor 102 and the second image sensor 103, respectively.

  FIG. 4B is an example of an image captured by the image capturing apparatus of the present embodiment on the second image sensor 103. In FIG. 4B, two faces that are main subjects are detected. FIG. 4C shows the readout mode region of the corresponding first image sensor 102 from the focus detection result of the second image sensor 103.

  The features of the imaging apparatus of the present embodiment are as follows. First, the divided area determined to be the main subject and the surrounding divided areas are areas that may be subjected to refocus processing that focuses on the subject in that area when the refocus image is generated later. It is done. Therefore, an A image (or B image) and an A + B image are read out as output signals of the divided pixels of the regions 503 and 504, which are the divided regions in FIG. Here, the mode in which the A image and the A + B image are read is referred to as a first reading mode.

  In the above description, only the signals of the divided pixels included in the divided area including the subject are read out in the first readout mode. However, the present invention is not limited to this, and is included in the divided area 504 adjacent to the divided area. The signal of the divided pixel may be read out in the first reading mode.

  On the other hand, other divided areas, which are determined to have no main subject, are considered to be areas that will not be refocused later. Therefore, in the readout mode, the signal of the divided pixels in the divided area is read out as an addition signal of the A + B image. Even when the main subject is not detected in step S406, it is considered that the region is not subjected to refocus processing later, so step S417 reads the entire region as an addition signal of the A + B image. As a result, it is possible to suppress the read signal and suppress the size of the generated image file.

  Next, when the person photographing mode is not set in step S401, the process proceeds to step S412 and the focus state of the photographing lens 200 is detected using the second image sensor 103. From the focus detection result in step S412, the defocus amount of the taking lens 200 is calculated in step S413, and the drive amount of the taking lens 200 is determined based on the defocus amount. In step S414, the actuator 202 as an adjusting unit drives the focus lens 210 based on the lens driving amount.

  Thereafter, in step S415, it is determined that the output signal of the first image sensor 102 is read out in the A + B image or the first readout mode, and the first image sensor 102 performs imaging in step S408.

  As mentioned above, although embodiment of the imaging device concerning embodiment of this invention was described using FIGS. 2-4, this invention is not limited to this and can take various forms. .

[Example 2]
Next, an imaging apparatus according to the second embodiment will be described. A description of the same configuration as that of the first embodiment will be omitted, and differences will be mainly described.

[Description of imaging device]
FIG. 5 is a schematic view of the interchangeable lens camera of the present embodiment. A light beam from a subject (not shown) is guided to a main mirror 601 in the imaging apparatus 600 via a focus lens 201 in the photographing lens 200. The main mirror 601 is disposed obliquely with respect to the optical axis in the photographing optical path, and guides the light beam from the subject to the finder optical system disposed above and outside the photographing optical path. It is possible to move to the second position for retraction.

  The central portion of the main mirror 601 is a half mirror, and when the main mirror 601 is down to the first position, a part of the light beam from the subject is transmitted through the half mirror portion. The transmitted light beam is reflected by a sub mirror 602 provided on the back side of the main mirror 601 and guided to a second image sensor 607 having a focus detection unit. On the other hand, the light beam reflected by the main mirror 601 forms an image on a focus plate 603 disposed at a position optically conjugate with the first image sensor 102.

  In the present embodiment, the size of the entire image sensor of the second image sensor 607 used for focus detection is smaller than that of the first image sensor 102 used for imaging. However, the pixel pitch is substantially the same in order to facilitate the pixel position comparison of each image sensor. More specifically, the size of each pixel is substantially the same, but the size of the image sensor is made smaller than that of the first image sensor 102. Therefore, the pixel density is substantially the same, but the number of pixels of the entire image sensor is smaller than that of the first image sensor 102.

  With such a configuration, the amount of image signal data captured by the second image sensor 607 is reduced, and the calculation processing time for focus evaluation is further reduced. Furthermore, since the size of the second image sensor 607 is reduced, the manufacturing cost and assembly cost of the second image sensor 607 are reduced.

  Next, the light (subject image) diffused by the focus plate 603 and transmitted therethrough is converted into an erect image by the penta roof prism 604. The erect image is magnified by the eyepiece 605 and observed by the user. When the main mirror 601 is raised to the second position, the sub mirror 602 is also folded with respect to the main mirror 601 and retracted out of the photographing optical path, and the light flux from the photographing lens 201 is changed to the first image sensor 102. To.

[Operation in portrait mode]
FIG. 6 is a diagram illustrating a flowchart of the shooting operation of the imaging apparatus according to the present embodiment. In the figure, the same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof is omitted.

  This operation starts when the user operates an operation member (not shown) of the camera 100 to turn on the power switch and set the shooting mode by the shooting mode selector. At this time, the main mirror 601 is lowered to the first position.

  Steps S401 to S406 are the same as in the first embodiment. In step S401, it is determined whether the person shooting mode is selected. If it is set, the process proceeds to step S402, where the second image sensor 607 is selected. To detect the focus. From this result, the defocus amount of the taking lens 200 is calculated in step S403, and the focus lens 210 is driven in step S404.

  Next, face detection is performed in step S405, and in step S406, if a face that is a main subject is detected in the second imaging element 607 region, step S1002 is performed. If not detected, step S1003 is performed. A reading mode of the first image sensor 102 described later is selected. In step S1004, the main mirror 601 is moved to the second position where the main mirror 601 is retracted out of the photographing optical path. In step S408, the first image sensor 102 reads an output signal in accordance with the selected reading mode and performs imaging. .

  Here, a signal reading mode will be described with reference to FIG. FIG. 7 shows the divided areas of the first image sensor 102 and the second image sensor 607 of the image pickup apparatus according to the present embodiment superimposed on each other. The first image sensor 102 divides the light receiving area into 64 × 8 × 8 areas, and the divided area is referred to as a divided area 801. A divided area corresponding to the upper left of the screen is d00, and d00 to d77 as shown in FIG. The second image sensor 607 is smaller than the first image sensor 102, and the light receiving area is referred to as a 6 × 6 36-divided area 802. The divided areas are d11 to d66, and are substantially at the same positions as the divided areas of the first image sensor.

  Here, in order to make the structure easy to understand, each division is defined, but it is not limited to this. As an example, when FIG. 4B is captured, the area 503 and the area 504 shown in FIG. 4C are read in the first readout mode. The other areas are read as A + B images. Here, the entire regions d11 to d66, which are positions overlapping with the second image sensor 607, may be read in the first readout mode, and the other regions may be read in the A + B image.

  On the other hand, if no face is detected in step S406, the first image sensor 102 determines that there is no main subject in the areas d11 to d66 overlapping with the second image sensor 607. In the reading mode in step S1003, reading is performed as an A + B image. Then, the other areas are read as the first reading mode. As a result, it is possible to suppress the read signal and suppress the size of the generated image file.

  Next, when the person photographing mode is not set in step S401, the process proceeds to step S412 and the focus state of the photographing lens 200 is detected using the second image sensor 103. From the focus detection result in step S412, the defocus amount of the taking lens 200 is calculated in step S413, and the drive amount of the taking lens 200 is determined based on the defocus amount. In step S414, the focus lens 210 is driven. Thereafter, in step S415, it is determined that the output signal of the first image sensor 102 is read out in the A + B image or the first readout mode, and the first image sensor 102 performs imaging in step S408.

  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.

DESCRIPTION OF SYMBOLS 100 Camera main body 101 Main mirror 102 1st image sensor 103 2nd image sensor 107 Camera CPU
201 Photographic Lens 300 Pixel Unit of Image Sensor 301 Photoelectric Conversion Unit of Pixel Unit of Image Sensor 303 Micro Lens

Claims (6)

A light beam splitting means (101) for splitting the light beam (305) that has passed through the taking lens into a plurality of light beams;
A first image sensor (102) that receives one of the divided light beams (305), and a second image sensor (103) that receives the other light beam;
Each of the first and second image sensors (102) and (103) has a plurality of pixel portions (300), and the pixel portion (300) has a pair of photoelectric conversion portions (301A, 301B) per one pixel portion. )
Focus detection is performed using the signal acquired by the second image sensor (103), and focus information is acquired.
In accordance with the result of the focus information, the image sensor includes a determination unit that determines a pixel signal readout mode and a range of the first image sensor (102),
In the readout mode, the first signal output obtained by independently reading the signals of the plurality of photoelectric conversion units (301A, 301B) and the second output signal read out by adding the signals of the plurality of photoelectric conversion units are read. Among these, the imaging is characterized in that either the first readout mode for reading out both the first signal output and the second signal output or the second readout mode for reading out only the second signal output. apparatus. The result of the focus information is to recognize the main subject by processing the focus detection result. When the main subject is detected in the second image sensor region, a region near the main subject The imaging apparatus according to claim 1, wherein the image reading device is read in the first read mode, and another area is read in the second read mode. 3. The image pickup apparatus according to claim 1, wherein when the main subject is not detected in the second image pickup device region, reading is performed in the second read mode.
The second image sensor (103) has the same light receiving area as the first image sensor (102), and has a smaller number of pixels than the first image sensor. The imaging device according to any one of the above. When the main subject is not detected in the second image sensor area, the area of the first image sensor (102) overlapping the second image sensor (103) is the second readout mode. The imaging apparatus according to claim 1, wherein reading and other areas are read in the first reading mode. The imaging apparatus according to any one of claims 1 to 5, wherein the second imaging element (607) has a light receiving area smaller than that of the first imaging element (102).