JP2013130763A - Imaging device, method for controlling the same, and program - Google Patents

Abstract

The accuracy of focus control is improved.
An imaging apparatus includes an acquisition unit and a focus control unit. The acquisition unit acquires a first image generated by the imaging unit at a first timing and a second image generated by the imaging unit at a second timing during a wobbling operation for reciprocating the focus lens in the optical axis direction. To do. Here, the first timing is a timing at which the position of the focus lens reaches one end in the moving range of the wobbling operation. The second timing is a timing when the position of the focus lens reaches the other end in the moving range. The focus control unit performs focus control by estimating the in-focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.
[Selection] Figure 2

Description

  The present technology relates to an imaging apparatus. Specifically, the present invention relates to an imaging apparatus that performs focus control, a control method thereof, and a program that causes a computer to execute the method.

  In recent years, imaging devices such as digital video cameras (for example, a camera-integrated recorder) that capture images of subjects such as landscapes and people to generate images (image data) and record the generated images as image contents have become widespread. ing. In addition, in order to prevent a failure of an imaging operation due to a user operation, many imaging devices that automatically perform focus control have been proposed.

  For example, an imaging apparatus that estimates a position to move a focus lens using two images captured at different focal lengths has been proposed (see, for example, Patent Document 1).

JP 2011-128623 A

  In the above-described conventional technology, since focus control can be performed using two images captured at different focal lengths, it is not necessary to provide an additional device for performing focus control in the imaging apparatus.

  As described above, since the above-described conventional technique uses two images picked up at different focal lengths, it is important to appropriately acquire these two images and improve the accuracy of focus control.

  The present technology has been created in view of such a situation, and aims to improve the accuracy of focus control.

  The present technology has been made to solve the above-described problems. The first aspect of the present technology is that the position of the focus lens is the wobbling operation during the wobbling operation of reciprocating the focus lens in the optical axis direction. The first image generated by the imaging unit at the first timing when reaching one end in the moving range, and the imaging unit at the second timing when the position of the focus lens reaches the other end in the moving range An acquisition unit that acquires the second image generated by the above, and a focus control by estimating a focus position of the focus lens by performing a two-image matching process using the acquired first image and second image. An imaging device including a focus control unit that performs the control, a control method thereof, and a program that causes a computer to execute the methodThus, during the wobbling operation, the first image generated by the imaging unit at the first timing and the second image generated by the imaging unit at the second timing are acquired, and the acquired first image and first image By performing the two-image matching process using the two images, the focus position of the focus lens is estimated and the focus control is performed.

  Further, in the first aspect, the acquisition unit is configured so that the interval between the first timing and the second timing becomes a predetermined interval based on an imaging cycle of the imaging unit and an operation cycle of the wobbling operation. The first timing and the second timing may be determined. Accordingly, the first timing and the second timing are determined based on the imaging period of the imaging unit and the operation period of the wobbling operation so that the interval between the first timing and the second timing becomes a predetermined interval. Bring.

  In addition, according to a second aspect of the present technology, the first image generated at the first timing among the plurality of images generated by the imaging unit, and the amplitude of the light source having a predetermined frequency included in the plurality of images. A two-image matching process using the acquisition unit that acquires the second image generated at the second timing at which the absolute value of the first value is the same as the first timing, and the acquired first image and second image Accordingly, there is provided an imaging apparatus including a focus control unit that performs focus control by estimating a focus position of the focus lens, a control method thereof, and a program that causes a computer to execute the method. Thus, the first image generated at the first timing among the plurality of images generated by the imaging unit and the absolute value of the amplitude of the light source having a predetermined frequency included in the plurality of images are the same as the first timing. The second image generated at the second timing is acquired, and by performing the two-image matching process using the acquired first image and second image, the focus position of the focus lens is estimated. This brings about the effect of performing focus control.

  In the second aspect, the acquisition unit may be configured such that the interval between the first timing and the second timing is a predetermined interval based on the imaging cycle of the imaging unit and the predetermined frequency. The timing and the second timing may be determined. Thereby, the first timing and the second timing are determined based on the imaging cycle of the imaging unit and the predetermined frequency so that the interval between the first timing and the second timing becomes the predetermined interval.

  According to the present technology, it is possible to achieve an excellent effect that the accuracy of focus control can be improved.

1 is a block diagram illustrating an internal configuration example of an imaging apparatus 100 according to a first embodiment of the present technology. It is a block diagram showing an example of functional composition of imaging device 100 in a 1st embodiment of this art. It is a figure showing typically an example of 2 image matching processing by focus control part 280 in a 1st embodiment of this art. It is a figure which shows the fitting curve which shows the correlation with the distance from the focus position of the focus lens in the 1st Embodiment of this technique, and the calculation result of 2 image matching process. It is a figure showing typically acquisition timing of two images used for two image matching processing by focus control part 280 in a 1st embodiment of this art. 12 is a flowchart illustrating an example of a two-image matching AF process procedure by the imaging apparatus 100 according to the first embodiment of the present technology. It is a figure which shows the fitting curve which shows the correlation with the distance from the focus position of the focus lens in the 2nd Embodiment of this technique, and the calculation result of 2 image matching process. It is a figure showing typically acquisition timing of two images used for two image matching processing by focus control part 280 in a 2nd embodiment of this art. 12 is a flowchart illustrating an example of a two-image matching AF process procedure by the imaging apparatus 100 according to the second embodiment of the present technology.

Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order.
1. First Embodiment (Focus control: an example in which two images used for two-image matching processing are acquired at a predetermined timing during a wobbling operation)
2. Second Embodiment (Focus Control: Example in which two images used for two-image matching processing are acquired at a predetermined timing when an artificial light source that is turned on by an AC power source is included in the subject)

<1. First Embodiment>
[Example of internal configuration of imaging device]
FIG. 1 is a block diagram illustrating an internal configuration example of the imaging apparatus 100 according to the first embodiment of the present technology.

  The imaging apparatus 100 includes an imaging lens 101, an imaging element 102, an analog signal processing unit 103, an A / D (Analog / Digital) conversion unit 104, and a digital signal processing unit 105. In addition, the imaging apparatus 100 includes a liquid crystal panel 106, a viewfinder 107, a recording device 108, a subject detection unit 109, a gyro sensor 110, and a control unit 120. The imaging apparatus 100 also includes an EEPROM (Electrically Erasable and Programmable Read Only Memory) 131. Further, the imaging apparatus 100 includes a ROM (Read Only Memory) 132 and a RAM (Random Access Memory) 133. The imaging apparatus 100 also includes an operation unit 140, a TG (Timing Generator) 151, a motor driver 152, a focus lens drive motor 153, and a zoom lens drive motor 154. The imaging apparatus 100 is realized by, for example, a digital still camera or a digital video camera (for example, a camera-integrated recorder) capable of performing AF (Auto Focus) processing.

  The imaging lens 101 is a lens that collects light from a subject and supplies the collected light to the imaging element 102, and includes a zoom lens, a focus lens, an iris, an ND (Neutral Density) mechanism, and a shift image stabilization type. It consists of a camera shake correction lens and the like. The zoom lens is a lens for continuously changing the focal length. The focus lens is a lens for focusing on the subject. The iris is for changing the diameter of the diaphragm. The ND mechanism is a mechanism for inserting an ND filter. The shift image stabilization type camera shake correction lens is a lens for correcting vibrations of the user's hand during the imaging operation. The focus lens is driven by a focus lens drive motor 153 and moves back and forth with respect to the subject. Thereby, the focus function is realized. The zoom lens is driven by a zoom lens drive motor 154 and moves back and forth with respect to the subject. Thereby, a zoom function is realized.

  The imaging element 102 is a photoelectric conversion element that receives light from a subject incident through the imaging lens 101 and converts the light into an electrical signal (image signal), and an image signal (analog signal) generated by the conversion. Is supplied to the analog signal processing unit 103. That is, an optical image of a subject incident through the imaging lens 101 is formed on the imaging surface of the imaging element 102, and the imaging element 102 performs an imaging operation in this state, thereby generating an image signal (analog signal). The The image sensor 102 is driven by the TG 151. As the image sensor 102, a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS), or the like can be used.

  The analog signal processing unit 103 performs analog processing such as noise removal on the image signal (analog signal) supplied from the image sensor 102 based on the control of the control unit 120. Then, the analog signal processing unit 103 supplies the image signal (analog signal) subjected to the analog processing to the A / D conversion unit 104.

  The A / D conversion unit 104 converts the image signal (analog signal) supplied from the analog signal processing unit 103 into a digital signal based on the control of the control unit 120, and this A / D converted image A signal (digital signal) is supplied to the digital signal processing unit 105.

  The digital signal processing unit 105 performs digital processing such as gamma correction on the image signal (digital signal) supplied from the A / D conversion unit 104 based on the control of the control unit 120, and is subjected to digital processing. The obtained image signal (digital signal) is supplied to each unit. For example, the digital signal processing unit 105 supplies an image signal (digital signal) that has been subjected to digital processing to the liquid crystal panel 106 and the viewfinder 107 for display. The digital signal processing unit 105 performs compression processing on the digitally processed image signal (digital signal), and supplies the recording device 108 with the compressed image data (compressed image data) for recording. Let

  The liquid crystal panel 106 is a display panel that displays each image based on the image signal (image data) supplied from the digital signal processing unit 105. For example, the liquid crystal panel 106 displays the image signal (image data) supplied from the digital signal processing unit 105 as a through image. For example, the liquid crystal panel 106 displays the image data recorded in the recording device 108 as a list image. As the liquid crystal panel 106, for example, a display panel such as an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescence) panel can be used.

  The viewfinder 107 is an electronic view finder (EVF) that displays each image based on the image signal (image data) supplied from the digital signal processing unit 105.

  The recording device 108 is a recording device that records the image signal (image data) supplied from the digital signal processing unit 105. In addition, the recording device 108 supplies the recorded image data to the digital signal processing unit 105. Note that the recording device 108 may be built in the imaging apparatus 100 or detachable from the imaging apparatus 100. Further, a flash memory or a DV tape can be used as the recording device 108.

  The subject detection unit 109 analyzes the image signal (image data) supplied from the digital signal processing unit 105 based on the control of the control unit 120 and detects a subject included in the image. The result (detection information) is output to the control unit 120. For example, the subject detection unit 109 detects the face of a person included in an image corresponding to the image signal (image data) supplied from the digital signal processing unit 105, and sends the face information regarding the detected face to the control unit 120. Output. As a face detection method, for example, a face detection method (for example, refer to Japanese Patent Application Laid-Open No. 2004-133737) based on matching between a template in which luminance distribution information of a face is recorded and an actual image, a skin color part included in image data, or a human being A face detection method or the like based on the face feature amount or the like can be used. Further, the face detection information includes the position and size of the detected face on the image. The subject detection unit 109 has a function of recognizing a subject that follows AF with respect to the image signal (image data) supplied from the digital signal processing unit 105.

  The gyro sensor 110 detects the angular velocity of the imaging device 100 and outputs the detected angular velocity to the control unit 120. By detecting the angular velocity of the imaging apparatus 100 by the gyro sensor 110, a change in the attitude of the imaging apparatus 100 is detected. It should be noted that the acceleration, movement, tilt, etc. of the imaging apparatus 100 are detected using a sensor other than the gyro sensor (for example, an acceleration sensor), and the orientation of the imaging apparatus 100 and its change are detected based on the detection result. May do

  The control unit 120 includes a CPU (Central Processing Unit), and controls various processes executed by the imaging apparatus 100 based on a program stored in the ROM 132. For example, the control unit 120 performs each process for realizing each function such as an AF function for focusing on a subject, an AE (Auto Exposure) function for adjusting brightness, and a WB (White Balance) function for white balance. Do. Further, the control unit 120 outputs to the motor driver 152 control information related to the focus lens based on focus tracking according to AF, manual operation, and zoom operation, control information related to the zoom lens based on the zoom operation, and the like.

  The EEPROM 131 is a non-volatile memory that can hold data even when the imaging apparatus 100 is powered off, and stores image data, various auxiliary information, and various setting information.

  The ROM 132 is a memory that stores programs used by the control unit 120, operation parameters, and the like.

  The RAM 133 is a working memory that stores programs used by the control unit 120, parameters that change as appropriate during the execution, and the like.

  The operation unit 140 receives operation input from the user such as a REC button (recording button), zoom operation, touch panel operation, and the like, and supplies the content of the received operation input to the control unit 120.

  The TG 151 generates a drive control signal for driving the image sensor 102 based on the control of the control unit 120 and drives the image sensor 102.

  The motor driver 152 drives each lens (focus lens, zoom lens, etc.) by driving the focus lens driving motor 153 and the zoom lens driving motor 154 based on the control of the control unit 120. That is, the motor driver 152 converts a control signal (control information for moving each motor) output from the control unit 120 into a voltage, and the converted voltage is a focus lens driving motor 153 and a zoom lens driving motor 154. Output to. The motor driver 152 drives each motor to drive each lens.

  The focus lens drive motor 153 is a motor that moves the focus lens based on the voltage output from the motor driver 152. The zoom lens drive motor 154 is a motor that moves the zoom lens based on the voltage output from the motor driver 152.

[Functional configuration example of imaging device]
FIG. 2 is a block diagram illustrating a functional configuration example of the imaging apparatus 100 according to the first embodiment of the present technology.

  The imaging apparatus 100 includes an imaging unit 210, an image processing unit 220, a recording control unit 230, a content storage unit 240, a display control unit 250, a display unit 260, a control unit 270, an image holding unit 271, A focus control unit 280 and an operation reception unit 290 are provided.

  The imaging unit 210 generates image data (image signal), and outputs the generated image data to the image processing unit 220. Further, the imaging unit 210 realizes an AF function by moving the focus lens based on the control of the focus control unit 280. Note that the imaging unit 210 corresponds to, for example, the imaging lens 101, the imaging element 102, the focus lens driving motor 153, and the zoom lens driving motor 154 shown in FIG.

  The image processing unit 220 performs various image processing on the image data output from the imaging unit 210 based on an instruction from the control unit 270. The image processing unit 220 displays the image data subjected to the various image processing, The data is output to the control unit 250 and the control unit 270. The image processing unit 220 corresponds to, for example, the analog signal processing unit 103, the A / D conversion unit 104, and the digital signal processing unit 105 illustrated in FIG.

  The recording control unit 230 performs recording control on the content storage unit 240 based on an instruction from the control unit 270. For example, the recording control unit 230 causes the content storage unit 240 to record the image data output from the image processing unit 220 as image content (a still image file or a moving image file). Note that the recording control unit 230 corresponds to, for example, the digital signal processing unit 105 and the control unit 270 illustrated in FIG.

  The content storage unit 240 is a recording medium that stores various types of information (such as image content) based on the control of the recording control unit 230. The content storage unit 240 corresponds to, for example, the recording device 108 illustrated in FIG.

  The display control unit 250 displays the image output from the image processing unit 220 on the display unit 260 based on an instruction from the control unit 270. The display control unit 250 corresponds to, for example, the digital signal processing unit 105 and the control unit 120 illustrated in FIG.

  The display unit 260 is a display panel that displays each image based on the control of the display control unit 250. The display unit 260 corresponds to, for example, the liquid crystal panel 106 and the viewfinder 107 illustrated in FIG.

  The control unit 270 controls each unit in the imaging apparatus 100 based on a control program stored in a memory (not shown). For example, the control unit 270 acquires two images used for the two-image matching process at a predetermined timing, and outputs the acquired two images to the focus control unit 280. This acquisition method will be described in detail with reference to FIGS. The control unit 270 corresponds to, for example, the control unit 120 illustrated in FIG. The control unit 270 is an example of an acquisition unit described in the claims.

  The image holding unit 271 is a holding unit that temporarily holds an image acquired by the control unit 270. Note that the image holding unit 271 corresponds to, for example, the RAM 133 illustrated in FIG.

  The focus control unit 280 performs the two-image matching process using the two images (first image and second image) acquired by the control unit 270, thereby estimating the focus position of the focus lens and performing focus control. Is what you do. The two-image matching process will be described in detail with reference to FIG. The focus control unit 280 corresponds to, for example, the control unit 120 and the motor driver 152 illustrated in FIG.

  The operation reception unit 290 is an operation reception unit that receives an operation performed by the user, and outputs a control signal (operation signal) corresponding to the received operation content to the control unit 270. Note that the operation reception unit 290 corresponds to, for example, the operation unit 140 illustrated in FIG.

[Two image matching processing example]
FIG. 3 is a diagram schematically illustrating an example of the two-image matching process performed by the focus control unit 280 according to the first embodiment of the present technology. Note that the horizontal axis shown in FIG. 3 is an axis indicating the position of the focus lens.

  The two-image matching process is a process of estimating the in-focus position by matching two images generated by shifting the position of the focus lens (see, for example, Japanese Patent Application Laid-Open No. 2011-128623). The two-image matching AF process is an AF process that moves the focus lens based on the in-focus position estimated by the two-image matching process (see, for example, Japanese Patent Application Laid-Open No. 2011-128623).

  In FIG. 3, the images 331 and 332 generated by the imaging unit 210 are shown at the position of the focus lens at the time of generation. The image 331 is generated at the position A of the focus lens, and the image 332 is generated at the position B of the focus lens. Note that the image 331 is clearer than the image 332.

  In the two-image matching process, the distance (arrow 336) to the in-focus position (arrow 335) is estimated using two images 331 and 332 generated at the positions of two different focus lenses. Further, the accuracy can be improved by performing this calculation a plurality of times.

Here, the blur change regarding the images 331 and 332 can be modeled by the image conversion function P given by the following Expression 1. In Equation 1, it shows an image 331 at _{f A,} shows an image 332 at _{f B.}
f _A * P = f _B ... Formula 1

Here, * represents a two-dimensional convolution. Further, the image conversion function P can be approximated by using a series of convolutions by the blur kernel K as shown in the following Expression 2.
P = K * K * K * ... * K ... Equation 2

As the blur kernel K, for example, the following matrix can be used.

  Here, the amount of blur difference between the images 331 and 332 can be measured by the number of convolutions in Equation 2. That is, it can be measured by the number of convolutions until the images 331 and 332 match. An example of calculation results of this measurement is shown in FIG. In the actual measurement, it is preferable that the blur difference between the two images is obtained using an iterative process.

[Applicable curve example]
FIG. 4 is a diagram illustrating a fitting curve indicating the correlation between the distance from the focus position of the focus lens and the calculation result of the two-image matching process according to the first embodiment of the present technology. The horizontal axis shown in FIG. 4 indicates the position of the focus lens, and the vertical axis indicates the number of iterations (the number of convolutions in Equation 2).

  FIG. 4A shows an example of a fitting curve when the position of the focus lens is close (when the width is narrow) when two images used for the two-image matching process are acquired.

  FIG. 4B shows an example of a fitting curve when the position of the focus lens is far (when the width is wide) when acquiring two images used for two-image matching.

  Here, the number of repetitions of the vertical axis shown in FIG. 4 (the number of convolutions in Equation 2) is a value corresponding to the distance to the focus position of the focus lens. Specifically, when the number of repetitions on the vertical axis shown in FIG. 4 is “0”, it means that the position of the focus lens is the in-focus position. For example, in FIG. 4A, the vicinity of “10” on the horizontal axis is a position where the number of repetitions on the vertical axis is “0”. In FIG. 4B, the vicinity of the horizontal axis “4” is a position where the number of repetitions on the vertical axis is “0”. Further, it means that the position of the focus lens moves away from the in-focus position as the number of repetitions moves away from “0”. In this case, the positive / negative value of the number of repetitions means the moving direction of the focus lens.

  Here, comparing FIGS. 4A and 4B, when the width of the image used for the two-image matching is wide, the accuracy is obtained, whereas the width of the image used for the two-image matching is the same. If it is narrow, the accuracy cannot be obtained.

  Thus, the two-image matching process is performed using two images. Further, the two images used in the two-image matching process are acquired, for example, during a moving image capturing operation. In this case, it is important to provide a sufficient difference in the position of the focus lens at the time of acquisition of the two images to increase the accuracy of the estimated focus position. Therefore, in the first embodiment of the present technology, an example in which two images used for the two-image matching process are acquired with a sufficient difference in the position of the focus lens is shown.

[Two image acquisition timing examples]
FIG. 5 is a diagram schematically illustrating acquisition timings of two images used for the two-image matching process by the focus control unit 280 according to the first embodiment of the present technology.

  FIG. 5A shows the transition of the focus lens in time series. FIG. 5B shows images 1 to 12 generated by the imaging unit 210 in time series. In addition, the horizontal axis shown to Fig.5 (a) and (b) shows a time axis. The vertical axis shown in FIG. 5A indicates the position of the focus lens. FIG. 5B shows the relationship between the images 1 to 12 and the processes (411 to 413) connected by arrows.

  In the first embodiment of the present technology, the focus control unit 280 causes the focus lens to perform a wobbling operation during the moving image capturing operation. Here, the wobbling operation is an operation of reciprocating the focus lens in the optical axis direction as shown in FIG. For example, when the operating frequency of wobbling is 15 Hz, it means that the focus lens reciprocates 15 times per second in the optical axis direction.

  For example, it is assumed that the imaging frequency (image cycle) of the imaging unit 210 is 60 fps (frame per second) and the wobbling operating frequency is 15 Hz. In this case, the wobbling operation is performed for one cycle while four images are captured by the imaging unit 210.

  As described above, in order to increase the accuracy of the two-image matching process, it is important to separate the position of the focus lens when acquiring the two images used for the two-image matching process.

  Therefore, when the wobbling operation is performed on the focus lens, the image is displayed at the timing when the position of the focus lens becomes the near side (Near) and the timing when the position of the focus lens becomes the far side (Far). It is preferable to obtain.

  For example, a case is assumed where the imaging frequency of the imaging unit 210 is 60 fps and the wobbling operating frequency is 15 Hz. In this case, the wobbling operation is performed for one cycle while four images are captured by the imaging unit 210. For this reason, it is preferable to acquire two images at intervals of “2 + 4 × n frames” (n = 0, 1, 2, 3,...). FIG. 5A shows an example in which two images are acquired at intervals of “2 frames” (that is, n = 0) as indicated by arrows 421 to 426.

  Thus, for example, during the wobbling operation, the control unit 270 acquires the first image generated by the imaging unit 210 at the first timing and the second image generated by the imaging unit 210 at the second timing. . Here, the first timing is, for example, a timing at which the position of the focus lens reaches one end (for example, near side (Near)) in the moving range of the wobbling operation. The second timing is a timing at which the position of the focus lens reaches another end (for example, far side (Far)) in the moving range of the wobbling operation.

  Note that the acquisition timing of the two images may be set in the imaging apparatus 100 in advance or may be set by a user operation. For example, the control unit 270 determines the first timing and the second timing so that the interval between the first timing and the second timing becomes a predetermined interval based on the imaging cycle of the imaging unit 210 and the operation cycle of the wobbling operation. You may make it do.

  In this way, the focus control unit 280 performs the two-image matching processing 411 to 413 using two images acquired at intervals of “2 + 4 × n frames” (n = 0, 1, 2, 3,...). Thereby, the precision of an estimated focus position can be improved. Further, the focus control unit 280 performs AF processing (two-image matching AF processing) based on the obtained information about the estimated in-focus position. That is, the focus control unit 280 performs focus control so as to move the focus lens to the estimated focus position.

  Here, an image used for the two-image matching process will be described. In the case of performing the two-image matching process, for example, a center area (a certain ratio) in the captured image can be cut out and used for calculation during AF of a moving image. However, instead of the central area in the captured image, a specified area (area (for example, rectangular area) in the captured image) specified by the user of the imaging apparatus 100 may be cut out and used for the calculation. In this case, the user can focus on the subject that the user wants to focus on. However, at the outer periphery of the captured image, the focus position estimation accuracy deteriorates due to a phenomenon called lens aberration, and there is a possibility that the time required in the two-image matching AF mode in which AF processing is performed only by the two-image matching processing may be extended. For this reason, it is preferable to designate an area closer to the center in the captured image as the designated area.

[Operation example of imaging device]
FIG. 6 is a flowchart illustrating an example of a two-image matching AF process procedure performed by the imaging apparatus 100 according to the first embodiment of the present technology. In this processing procedure, an example is shown in which each time an image is generated by the imaging unit 210 when the moving image imaging mode is set. In this processing procedure, an example in which two images are acquired at an interval of “2 frames” (that is, n = 0) is shown.

  First, the control unit 270 determines whether one image (first image) used for the two-image matching process has been acquired (step S901). If the first image has not been acquired (step S901), the control unit 270 determines whether the position of the focus lens has reached either the near side or the far side peak of the wobbling operation. (Step S902). If the position of the focus lens has not reached any peak (step S902), the operation of the two-image matching AF process is terminated.

  In addition, when the position of the focus lens has reached either the near side or the far side peak of the wobbling operation (step S902), the control unit 270 selects an image (first image) used for the two-image matching process. Obtain (step S903). The first image acquired in this way is temporarily held in the image holding unit 271. Step S903 is an example of a first acquisition procedure described in the claims.

  If the first image has been acquired (step S901), the control unit 270 determines whether the position of the focus lens at the time of acquiring the first image is near or far from the wobbling operation. (Step S904).

  When the position of the focus lens at the time of acquiring the first image is near the wobbling operation (step S904), the control unit 270 determines whether or not the position of the focus lens has reached the far side peak of the wobbling operation. Is determined (step S905). If the position of the focus lens has not reached the peak on the far side (step S905), the two-image matching AF processing operation is terminated. If the position of the focus lens has reached the far side peak (step S905), the control unit 270 acquires an image (second image) used for the two-image matching process (step S906). Subsequently, the focus control unit 280 performs focus control by estimating the focus position of the focus lens by performing two-image matching processing using the acquired first image and second image (step S907).

  When the position of the focus lens at the time of acquisition of the first image is on the far side of the wobbling operation (step S904), the control unit 270 determines whether or not the position of the focus lens has reached a peak near the wobbling operation. Is determined (step S908). When the position of the focus lens has not reached the peak on the near side (step S908), the operation of the two-image matching AF process is terminated. When the position of the focus lens has reached the peak on the near side (step S908), the control unit 270 acquires an image (second image) used for the two-image matching process (step S909). Steps S906 and S909 are an example of a second acquisition procedure described in the claims.

  Subsequently, the focus control unit 280 performs focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image (step S910). Note that steps S907 and S910 are an example of a focus control procedure described in the claims.

  As described above, according to the first embodiment of the present technology, two images having a large difference in the position of the focus lens necessary for the two-image matching process can be acquired during the moving image capturing operation. Thereby, the accuracy of the two-image matching process during the moving image capturing operation can be improved. That is, the in-focus position can be estimated with high accuracy, and the accuracy of focus control can be improved.

<2. Second Embodiment>
In the first embodiment of the present technology, an example in which two images having a large difference in the position of the focus lens necessary for the two-image matching process is acquired during the moving image capturing operation has been described. Here, when an artificial light source that is turned on by an AC power supply is included in a subject, a phenomenon called flicker (flicker phenomenon) may occur depending on the combination of the video frequency of the imaging apparatus and the commercial power supply frequency. . This flicker phenomenon occurs because the voltage varies with time in an AC power supply. That is, it occurs because the intensity of the light source changes in accordance with the fluctuation of the voltage in the AC power source according to the time.

  For example, it is assumed that the two-image matching process is performed when the flicker phenomenon occurs. In this case, if two images are acquired at different times, there is a possibility that light of different intensity is captured in each image even with the same light source. In this case, the accuracy of the two-image matching process may be reduced.

  Therefore, in the second embodiment of the present technology, an example in which the in-focus position is accurately estimated when the two-image matching process is performed in a state where the flicker phenomenon occurs is shown. Note that the configuration of the imaging device according to the second embodiment of the present technology is substantially the same as the example illustrated in FIGS. For this reason, a part of description is abbreviate | omitted about the part which is common in 1st Embodiment of this technique.

[Applicable curve example]
FIG. 7 is a diagram illustrating a fitting curve indicating the correlation between the distance from the focus position of the focus lens and the calculation result of the two-image matching process according to the second embodiment of the present technology. The fitting curve shown in FIG. 7 is the same as the fitting curve shown in FIG. 4, the horizontal axis indicates the position of the focus lens, and the vertical axis indicates the number of iterations (the number of convolutions in Equation 2).

  FIG. 7A shows an example of a fitting curve when the two-image matching process is performed on a subject including a light source with flicker.

  FIG. 7B shows an example of a fitting curve when the two-image matching process is performed on a subject including a light source without flicker.

  Here, comparing FIGS. 7A and 7B, when the two-image matching process is performed on a subject including a light source without flicker, the calculation result is relatively stable. In contrast, when the two-image matching process is performed on a subject including a light source with flicker, the calculation result is very unstable. For this reason, it is important to improve the accuracy of the two-image matching process even when a subject including a flicker light source is an imaging target.

  Therefore, in the second embodiment of the present technology, an example in which two optimal images necessary for the two-image matching process are acquired during a moving image capturing operation when a subject including a flicker light source is an imaging target is shown. .

[Two image acquisition timing examples]
FIG. 8 is a diagram schematically illustrating acquisition timings of two images used for the two-image matching process by the focus control unit 280 according to the second embodiment of the present technology.

  FIG. 8A shows voltage transitions in time series. Further, FIG. 8B shows images 1 to 12 generated by the imaging unit 210 in time series. In addition, the horizontal axis shown to Fig.8 (a) and (b) shows a time axis. Moreover, the vertical axis | shaft shown to Fig.8 (a) shows the value of a voltage. FIG. 8B shows the relationship between the images 1 to 12 and the processes (451 to 453) by arrows, as in FIG. 5B.

  In the second embodiment of the present technology, the control unit 270 performs two-image matching at a timing at which the brightness (absolute voltage value) of two images matches for an assumed flicker light source during a moving image capturing operation. Two images used for processing are acquired. Hereinafter, these acquisition timings will be described in detail.

[Example of acquisition timing when imaging frequency of imaging apparatus 100 is 60 fps]
Here, a case where the imaging frequency of the imaging apparatus 100 is 60 fps will be described as an example.

  First, a light source driven by a 50 Hz AC power source is assumed. In this case, since the same brightness is obtained at intervals of 0.01 seconds, it is preferable to acquire two images at a time interval of (3/60) × n seconds (n = 1, 2, 3,...). . That is, as shown in FIG. 8B, it is preferable to acquire two images at intervals of 3 × n frames (n = 1, 2, 3,...) (Arrows 461 to 464). Two images acquired at such time intervals have the same brightness from the same light source.

  Next, a light source driven by a 60 Hz AC power supply is assumed. In this case, since the imaging frequency (60 fps) of the imaging device 100 and the AC power supply frequency (60 Hz) are the same, the two images are the same no matter what time interval is acquired. The light source has the same brightness.

[Example of acquisition timing when imaging frequency of imaging apparatus 100 is 50 fps]
Next, the case where the imaging frequency of the imaging apparatus 100 is 50 fps will be described as an example.

  First, a light source driven by a 50 Hz AC power source is assumed. In this case, since the imaging frequency (50 fps) of the imaging apparatus 100 and the frequency of the AC power supply (50 Hz) are the same, the two images are the same no matter what time interval is acquired. The light source has the same brightness.

  Next, a light source driven by a 60 Hz AC power supply is assumed. In this case, it is preferable to acquire two images at a time interval of (5/50) × n seconds (n = 1, 2, 3,...). That is, it is preferable to acquire two images at intervals of 5 × n frames (n = 1, 2, 3,...). Two images acquired at such time intervals have the same brightness from the same light source.

[Example of acquisition timing when imaging frequency of imaging device 100 is 48 fps]
Next, the case where the imaging frequency of the imaging apparatus 100 is 48 fps will be described as an example.

  First, a light source driven by a 50 Hz AC power source is assumed. In this case, it is preferable to acquire two images at a time interval of (12/48) × n seconds (n = 1, 2, 3,...). That is, it is preferable to acquire two images at intervals of 12 × n frames (n = 1, 2, 3,...). Two images acquired at such time intervals have the same brightness from the same light source.

  Next, a light source driven by a 60 Hz AC power supply is assumed. In this case, it is preferable to acquire two images at a time interval of (4/48) × n seconds (n = 1, 2, 3,...). That is, it is preferable to acquire two images at intervals of 4 × n frames (n = 1, 2, 3,...). Two images acquired at such time intervals have the same brightness from the same light source.

  As described above, the control unit 270 acquires two images generated at the first timing and the second timing among the plurality of images generated by the imaging unit 210. Here, when the first timing is an arbitrary timing, the absolute value of the amplitude (voltage absolute value) of the light source having a predetermined frequency included in the plurality of images is the same as the first timing. Is the timing.

  As described above, the accuracy of the estimated in-focus position can be increased by performing the two-image matching processing 451 to 453 using the two images acquired at predetermined intervals.

  Note that the acquisition timing of the two images may be set in the imaging apparatus 100 in advance or may be set by a user operation. Further, information regarding a location where the imaging apparatus 100 exists may be acquired and the imaging apparatus 100 may automatically set the information. For example, the location where the imaging device 100 exists can be estimated based on position information (latitude, longitude, altitude, etc.) calculated by a GPS (Global Positioning System) unit. And the control part 270 can acquire the frequency of the alternating current power supply of the location based on the estimation result, and can determine the acquisition timing of two images according to the frequency of this alternating current power supply.

  That is, the control unit 270 determines the first timing and the second timing so that the interval between the first timing and the second timing becomes a predetermined interval based on the imaging cycle of the imaging unit 210 and a predetermined frequency. Can do.

[Operation example of imaging device]
FIG. 9 is a flowchart illustrating an example of a two-image matching AF process procedure performed by the imaging apparatus 100 according to the second embodiment of the present technology. In this processing procedure, an example is shown in which each time an image is generated by the imaging unit 210 when the moving image imaging mode is set. Further, in this processing procedure, an example is shown in which an imaging frequency of the imaging apparatus 100 is 60 fps and an object including a light source driven by a 50 Hz AC power source is imaged.

  First, the control unit 270 determines whether one image (first image) used for the two-image matching process has been acquired (step S921). If the first image has not been acquired (step S921), the control unit 270 acquires an image (first image) used for the two-image matching process (step S922). The first image acquired in this way is temporarily held in the image holding unit 271. Step S922 is an example of a first acquisition procedure described in the claims. Subsequently, the control unit 270 sets the image acquisition counter to 0 (step S923).

  If the first image has been acquired (step S921), the control unit 270 adds 1 to the image acquisition counter (step S924), and determines whether the image acquisition counter is a multiple of 3. Judgment is made (step S925). If the image acquisition counter is not a multiple of 3 (step S925), the two-image matching AF processing operation is terminated.

  If the image acquisition counter is a multiple of 3 (step S925), the control unit 270 acquires an image (second image) used for the two-image matching process (step S926). Note that step S926 is an example of a first acquisition procedure described in the claims. Subsequently, the focus control unit 280 performs focus control by estimating the focus position of the focus lens by performing two-image matching processing using the acquired first image and second image (step S927). Step S927 is an example of the focus control procedure described in the claims.

  As described above, according to the second embodiment of the present technology, even when a subject including a flicker light source is an imaging target, two optimal images necessary for the two-image matching processing are acquired during the imaging operation of the moving image. can do. Thereby, the accuracy of the two-image matching process during the moving image capturing operation can be improved. That is, the in-focus position can be estimated with high accuracy, and the accuracy of focus control can be improved.

  That is, according to the embodiment of the present technology, when performing the two-image matching process, the acquisition timing of the two images used for the two-image matching process can be optimized. Thereby, the in-focus position can be estimated with high accuracy, and the accuracy of focus control can be improved.

  In the embodiment of the present technology, the imaging device 100 including the imaging unit 210 has been described as an example. However, the embodiment of the present technology may be applied to an imaging device (electronic device) to which the imaging unit can be attached and detached. it can. The embodiment of the present technology can be applied to electronic devices such as a mobile phone with an imaging function and a mobile terminal device with an imaging function (for example, a smartphone).

  The above-described embodiment shows an example for embodying the present technology, and the matters in the embodiment and the invention-specific matters in the claims have a corresponding relationship. Similarly, the invention specific matter in the claims and the matter in the embodiment of the present technology having the same name as this have a corresponding relationship. However, the present technology is not limited to the embodiment, and can be embodied by making various modifications to the embodiment without departing from the gist thereof.

  Further, the processing procedure described in the above embodiment may be regarded as a method having a series of these procedures, and a program for causing a computer to execute these series of procedures or a recording medium storing the program. You may catch it. As this recording medium, for example, a CD (Compact Disc), an MD (MiniDisc), a DVD (Digital Versatile Disk), a memory card, a Blu-ray Disc (registered trademark), or the like can be used.

In addition, this technique can also take the following structures.
(1) During the wobbling operation for reciprocating the focus lens in the optical axis direction, the first generated by the imaging unit at the first timing when the position of the focus lens reaches one end in the moving range of the wobbling operation. An acquisition unit that acquires an image and a second image generated by the imaging unit at a second timing when the position of the focus lens reaches the other end in the movement range;
An imaging apparatus comprising: a focus control unit that performs focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.
(2) The acquisition unit is configured to set the first timing and the second timing such that an interval between the first timing and the second timing is a predetermined interval based on an imaging cycle of the imaging unit and an operation cycle of the wobbling operation. The imaging apparatus according to (1), wherein two timings are determined.
(3) A first image generated at a first timing among a plurality of images generated by the imaging unit, and an absolute value of an amplitude of a light source having a predetermined frequency included in the plurality of images is the first timing. An acquisition unit that acquires a second image generated at a second timing that is the same as
An imaging apparatus comprising: a focus control unit that performs focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.
(4) The acquisition unit may be configured such that the first timing and the second timing are set such that an interval between the first timing and the second timing is a predetermined interval based on an imaging cycle of the imaging unit and the predetermined frequency. The imaging device according to (3), wherein:
(5) During the wobbling operation for reciprocating the focus lens in the optical axis direction, the first generated by the imaging unit at the first timing when the position of the focus lens reaches one end in the moving range of the wobbling operation. A first acquisition procedure for acquiring an image;
A second acquisition procedure for acquiring a second image generated by the imaging unit at a second timing when the position of the focus lens reaches the other end in the moving range during the wobbling operation;
A control method for an imaging apparatus, comprising: a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.
(6) a first acquisition procedure for acquiring a first image generated at a first timing among a plurality of images generated by the imaging unit;
A second acquisition procedure for acquiring a second image generated at a second timing at which an absolute value of an amplitude of a light source having a predetermined frequency included in the plurality of images is the same as the first timing;
A control method for an imaging apparatus, comprising: a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.
(7) During the wobbling operation for reciprocating the focus lens in the optical axis direction, the first generated by the imaging unit at the first timing when the position of the focus lens reaches one end in the moving range of the wobbling operation. A first acquisition procedure for acquiring an image;
A second acquisition procedure for acquiring a second image generated by the imaging unit at a second timing when the position of the focus lens reaches the other end in the moving range during the wobbling operation;
A program that causes a computer to execute a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.
(8) a first acquisition procedure for acquiring a first image generated at a first timing among a plurality of images generated by the imaging unit;
A second acquisition procedure for acquiring a second image generated at a second timing at which an absolute value of an amplitude of a light source having a predetermined frequency included in the plurality of images is the same as the first timing;
A program that causes a computer to execute a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.

DESCRIPTION OF SYMBOLS 100 Imaging device 101 Imaging lens 102 Imaging element 103 Analog signal processing part 104 A / D conversion part 105 Digital signal processing part 106 Liquid crystal panel 107 Viewfinder 108 Recording device 109 Subject detection part 110 Gyro sensor 120 Control part 131 EEPROM
132 ROM
133 RAM
140 Operation unit 151 TG
152 motor driver 153 focus lens driving motor 154 zoom lens driving motor 210 imaging unit 220 image processing unit 230 recording control unit 240 content storage unit 250 display control unit 260 display unit 270 control unit 271 image holding unit 280 focus control unit 290 operation reception unit

Claims (8)

During a wobbling operation for reciprocating the focus lens in the optical axis direction, a first image generated by the imaging unit at a first timing when the position of the focus lens reaches one end in the moving range of the wobbling operation; An acquisition unit that acquires a second image generated by the imaging unit at a second timing when the position of the focus lens reaches the other end in the moving range;
An imaging apparatus comprising: a focus control unit that performs focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.   The acquisition unit sets the first timing and the second timing so that an interval between the first timing and the second timing becomes a predetermined interval based on an imaging cycle of the imaging unit and an operation cycle of the wobbling operation. The imaging device according to claim 1 to be determined. The first image generated at the first timing among the plurality of images generated by the imaging unit and the absolute value of the amplitude of the light source having a predetermined frequency included in the plurality of images are the same as the first timing. An acquisition unit that acquires the second image generated at the second timing,
An imaging apparatus comprising: a focus control unit that performs focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.   The acquisition unit determines the first timing and the second timing so that an interval between the first timing and the second timing becomes a predetermined interval based on an imaging cycle of the imaging unit and the predetermined frequency. The imaging device according to claim 3. During the wobbling operation for reciprocating the focus lens in the optical axis direction, the first image generated by the imaging unit is acquired at the first timing when the position of the focus lens reaches one end in the moving range of the wobbling operation. A first acquisition procedure,
A second acquisition procedure for acquiring a second image generated by the imaging unit at a second timing when the position of the focus lens reaches the other end in the moving range during the wobbling operation;
A control method for an imaging apparatus, comprising: a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image. A first acquisition procedure for acquiring a first image generated at a first timing among a plurality of images generated by the imaging unit;
A second acquisition procedure for acquiring a second image generated at a second timing at which an absolute value of an amplitude of a light source having a predetermined frequency included in the plurality of images is the same as the first timing;
A control method for an imaging apparatus, comprising: a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image. During the wobbling operation for reciprocating the focus lens in the optical axis direction, the first image generated by the imaging unit is acquired at the first timing when the position of the focus lens reaches one end in the moving range of the wobbling operation. A first acquisition procedure,
A second acquisition procedure for acquiring a second image generated by the imaging unit at a second timing when the position of the focus lens reaches the other end in the moving range during the wobbling operation;
A program that causes a computer to execute a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image. A first acquisition procedure for acquiring a first image generated at a first timing among a plurality of images generated by the imaging unit;
A second acquisition procedure for acquiring a second image generated at a second timing at which an absolute value of an amplitude of a light source having a predetermined frequency included in the plurality of images is the same as the first timing;
A program that causes a computer to execute a focus control procedure for performing focus control by estimating a focus position of the focus lens by performing two-image matching processing using the acquired first image and second image.