JP2015129829A - imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device that can suppress flickers of an image, which are generated when displaying an image acquired with changing the optical zoom magnification.SOLUTION: An imaging device of the present invention includes: an optical system capable of changing the optical magnification by moving a plurality of lenses in the optical axis direction; a diaphragm having an aperture for allowing subject light taken in by the optical system to pass therethrough, and capable of adjusting the amount of light of the subject light by changing the diameter of the aperture; a detection section for detecting the position of the optical system; an exposure calculation section for calculating the exposure conditions when acquiring an image; and a correction section for correcting the exposure conditions on the basis of the position of the optical system detected by the detection section and the diameter of the aperture adjusted by the diaphragm when the optical magnification of the optical system is changed in the process of continuously acquiring a plurality of images.

Description

  The present invention relates to an imaging apparatus.

  An imaging apparatus typified by a digital camera calculates an exposure condition based on the luminance of a subject, and controls the aperture, shooting sensitivity, and shutter speed so as to satisfy the calculated exposure condition. When a still image is taken with this imaging apparatus, the angle of view is adjusted while observing the image displayed on the display unit. When shooting a moving image, the angle of view is adjusted during the shooting process. Here, the adjustment of the angle of view includes changing the optical magnification (optical zoom magnification) of the imaging optical system by operating a zoom change button provided in the imaging apparatus.

JP 2003-153073 A

  When the optical zoom magnification in the image pickup optical system is changed, the plurality of lenses constituting the image pickup optical system move in the optical axis direction, and the angle of view changes. With this change in the angle of view, the exposure conditions at the time of shooting, such as the aperture value (F value), change. When acquiring a through image obtained in the shooting standby state or when acquiring a moving image, the exposure condition is calculated with a predetermined interval. On the other hand, since the imaging process is executed at a cycle shorter than the cycle for calculating the exposure condition, the imaging apparatus uses the calculated exposure condition across a plurality of imaging processes. When a through image is acquired while changing the optical zoom magnification, or a moving image is acquired, the number of imaging processes executed until the next exposure condition is calculated is calculated as the number of imaging processes increases. The difference in condition between the exposure condition to be performed and the exposure condition assumed when the imaging process is executed increases. Therefore, there is a large brightness difference between the image acquired by the imaging process performed immediately before calculating the new exposure condition and the image acquired by the imaging process using the newly calculated exposure condition. As a result, when these images are displayed, flickering occurs due to a change in brightness between the images.

  An object of the present invention is to suppress flickering of an image that occurs when an acquired image is displayed while changing the optical zoom magnification.

  In order to solve the above-described problems, an imaging apparatus according to the present invention includes an optical system capable of changing an optical magnification by moving a plurality of lenses in the optical axis direction, and subject light captured by the optical system. A diaphragm having an aperture to pass through and capable of adjusting the amount of light of the subject light by changing the aperture diameter of the aperture, a detection unit for detecting the position of the optical system, and an exposure condition at the time of image acquisition An exposure calculation unit that calculates the position of the optical system detected by the detection unit when the optical magnification of the optical system is changed in the process of continuously acquiring the plurality of images, and the position of the optical system And a correction unit that corrects the exposure condition based on the aperture diameter of the diaphragm.

  According to the present invention, it is possible to suppress flickering of an image that occurs when an acquired image is displayed while changing the optical zoom magnification.

It is a functional block diagram which shows an example of the electronic camera which implemented this invention. It is a figure which shows an example of an aperture value table. It is a figure which shows an example of the correspondence of a zoom position and an aperture value (Av value). It is a flowchart which shows the flow at the time of imaging. It is a figure which shows an example of the timing chart in the case of video recording, without changing an optical zoom magnification. It is a figure which shows an example of the timing chart in the case of moving image shooting by changing the optical zoom magnification.

  Hereinafter, an electronic camera will be described as an example of an imaging apparatus embodying the present invention. The electronic camera 10 can perform moving image shooting for shooting moving images in addition to still image shooting for shooting still images. In addition, the electronic camera 10 can display a through image on the display unit 28 described later in a shooting standby state in which a shooting start operation for still image shooting or moving image shooting is not performed. Here, the shooting start operation is to operate a shooting operation unit represented by the release button 43, for example. Furthermore, the electronic camera 10 can display the acquired moving image on the display unit 28 even during moving image shooting.

  As shown in FIG. 1, the electronic camera 10 includes an imaging optical system 15, an imaging device 16, an A / D converter 17, a lens driving unit 19, an aperture driving unit 20, a timing generator (TG) 21, a buffer memory 25, an image. A processing unit 26, a display control unit 27, a display unit 28, a connection I / F 29, a photometric sensor 30, a CPU 40, a built-in memory 41, a work memory 42, a release button 43, an operation unit 44, and the like are provided. Here, the A / D converter 17, the buffer memory 25, the image processing unit 26, the display control unit 27, the photometric sensor 30, the CPU 40, the built-in memory 41 and the work memory 42 are electrically connected via a bus 45. .

  The imaging optical system 15 includes a plurality of lenses such as a zoom lens and a focus lens. Among these lenses, the zoom lens moves in the optical axis (L) direction when the optical zoom magnification is changed. Further, the focus lens slightly moves in the direction of the optical axis (L) when adjusting the focus. The movement of each lens constituting the imaging optical system 15 is executed by the lens driving unit 19. Although not shown, the lens driving unit 19 includes a driving mechanism such as a gear mechanism or a helicoid mechanism in addition to a stepping motor.

  The imaging optical system 15 includes a diaphragm 46. The diaphragm 46 has an aperture through which the subject light taken in by the imaging optical system 15 is transmitted, and the amount of the subject light is adjusted by adjusting the aperture diameter of the aperture. The diaphragm 46 is actuated by the diaphragm driving unit 20 and its opening diameter is adjusted.

  For example, a CCD image sensor or a CMOS image sensor is used as the imaging element 16. The image sensor 16 includes a plurality of pixels. The image sensor 16 receives the subject light (incident light) captured by the imaging optical system 15 at each pixel and converts it into signal charges. A voltage signal based on this signal charge is output as a pixel signal of each pixel. A signal obtained by collecting pixel signals output from the plurality of pixels is an image signal. This image signal is input to the A / D converter 17 after being subjected to processing such as clamping processing and correlated double sampling (CDS) processing. Note that the image sensor 16 is controlled by a timing generator (TG) 21.

  The A / D converter 17 converts the image signal output from the image sensor 16 from an analog signal to a digital signal. This digitized image signal is written in the buffer memory 25 as image data.

  The image processing unit 26 performs image processing such as white balance processing, color interpolation processing, contour compensation processing, and gamma processing on the image data written in the buffer memory 25. The image data subjected to this image processing is stored in the buffer memory 25. When storing an image obtained at the time of shooting, the CPU 40 reads out the image data stored in the buffer memory 25 and writes the image data and information at the time of shooting to the storage medium 47 as one image file. .

  The display unit 28 is composed of, for example, an LCD panel or an EL display panel. The display unit 28 displays an image for setting in addition to a through image and an image (still image and moving image) obtained by photographing. The image display on the display unit 28 is controlled by the display control unit 27.

  The connection I / F 29 is electrically connected to the storage medium 47 attached to the electronic camera 10. By this electrical connection between the connection I / F 29 and the storage medium 47, it is possible to write data to the storage medium 47 and read data stored in the storage medium 47. Examples of the storage medium 47 include a memory card made of a flash memory, an optical disk, and a hard disk drive that can be externally connected to the electronic camera 10.

  The photometric sensor 30 detects the brightness (luminance) of the subject and outputs a detection signal to the CPU 40. In the present embodiment, the luminance of the subject is detected using the photometric sensor 30, but the present invention is not limited to this, and the luminance of the subject is detected using the image signal output from the image sensor 16. Is also possible.

  The CPU 40 controls each unit of the electronic camera 10 by executing a control program stored in the built-in memory 41. When controlling each part of the electronic camera 10, the CPU 40 receives a signal based on the operation of the release button 43 and the operation part 44 and a signal from each part of the electronic camera 10, and the CPU 40 executes processing based on the input signal. To do. The built-in memory 41 stores a control program executed by the CPU 40 and data to be referred to when executing the control program. Here, the CPU 40 executes an imaging process in conjunction with the output of a vertical synchronization signal, for example. If the time interval at which this vertical synchronization signal is output is 1 VD, this 1 VD is, for example, 33 ms. Since the time interval at which the vertical synchronization signal is output is set based on the frame rate at the time of moving image shooting or through image acquisition, the time interval of 1 VD is not limited to 33 ms.

  The built-in memory 41 stores an aperture value table 53. As shown in FIG. 2, the aperture value table 53 is a table in which the zoom position, the aperture diameter of the aperture, and the aperture value determined by these are associated with each other. As is well known, the value indicating the zoom position is set to be smaller as it is closer to the wide-angle end and larger as it is closer to the telephoto end. Further, the aperture is indicated by the number of steps, and is set so that the smaller the number of steps, the closer to the open side (the larger the aperture diameter), and the larger the number of steps, the closer to the smaller aperture (the smaller the aperture diameter).

  The work memory 42 stores various calculation values calculated when the CPU 40 executes the control program and exposure condition data obtained by an exposure calculation described later.

  The release button 43 is operated when performing still image shooting or moving image shooting. The operation unit 44 includes a zoom button, a cross key, an execution button, etc. (not shown). The operation unit 44 is operated when performing initial setting of the electronic camera 10, setting of shooting conditions, and the like.

  The CPU 40 described above includes an exposure calculation unit 51 and a focus evaluation unit 52. The exposure calculation unit 51 calculates an exposure condition in the imaging process by executing an exposure calculation process and an exposure correction calculation process. Here, in moving image shooting or shooting of a through image in the shooting standby state, the exposure calculation processing is executed, for example, every time the vertical synchronization signal is output six times, that is, with a time interval of 6 VD (for example, 200 ms). . Note that the exposure calculation process is executed at a time interval of 6 VD, but it is not necessary to be limited to this as long as the processing time related to the exposure calculation process can be set short. It is also possible to set to an integer multiple, specifically nVD (n: an integer of 3 or more).

  This exposure calculation process is executed in the following procedure. The exposure calculation unit 51 calculates subject luminance based on the detection signal from the photometric sensor 30. Then, the exposure calculation unit 51 obtains the aperture value, shutter speed, and shooting sensitivity, respectively, using the calculated subject brightness. The exposure calculation unit 51 writes the calculated subject brightness, aperture value, shutter speed, and shooting sensitivity in the work memory 42.

  The exposure correction calculation processing is executed each time a vertical synchronization signal is output, for example, when the optical zoom magnification of the imaging optical system 15 is changed in moving image shooting or shooting of a through image in a shooting standby state. That is, the time interval of the exposure correction calculation process is set to 1VD. Although the time interval of the exposure correction calculation process is 1 VD, it is not limited to this, and may be mVD (m: an integer of 2 or more).

  This exposure correction calculation process is executed in the following procedure. The exposure calculation unit 51 obtains a correction value for the aperture value based on the zoom position at the time of the exposure calculation process, the aperture value obtained by the exposure calculation process, and the zoom position acquired when the exposure correction calculation process is started. .

  When the exposure condition obtained by the exposure calculation process is calculated, the CPU 40 reads the aperture value table 53 stored in the built-in memory 41. The CPU 40 reads the aperture value associated with each of the calculated aperture value and the zoom position from the aperture value table 53. The CPU 40 outputs a drive signal to the aperture drive unit 20. In response to this, the diaphragm drive unit 20 operates the diaphragm 46 so that the read aperture diameter is obtained. At the same time, the CPU 40 adjusts the shooting sensitivity of the image sensor 16 via the TG 21. In addition, when the release button 43 is operated, the CPU 40 causes the TG 21 to execute accumulation and readout of signal charges with respect to each pixel of the image sensor 16 based on the shutter speed obtained by the exposure calculation process described above. Output a control signal.

As described above, the lens driving unit 19 includes a stepping motor. The stepping motor is driven by receiving an electric pulse signal. Therefore, the exposure calculation unit 51 counts the number of electric pulse signals (hereinafter, the number of steps) when the stepping motor is driven, and uses the counted number of steps to position the zoom lens of the imaging optical system 15 (hereinafter, the zoom). (Referred to as position). When the obtained zoom position is between the zoom positions Z _n , Z _{n + 1} (n = 0, 1, 2,...), The exposure calculation unit 51 sets the aperture value (Av value) for the zoom position as follows ( 1) It calculates | requires using linear interpolation by Formula.

Av = Av _n + (Av _{n + 1} −Av _n ) × α (1)
Here, the coefficient α indicates the ratio of the distance from the zoom position Z _n to the obtained zoom position with respect to the distance from the zoom position Z _n to the zoom position Z _{n + 1} . The coefficient α uses the number of steps when the zoom lens moves from the zoom position Z _n to the zoom position Z _{n + 1} and the number of steps when the zoom lens moves from the zoom position Z _n to the obtained zoom position. Is required. The exposure calculation unit 51 obtains a correction value for the aperture value by subtracting the aperture value obtained by the exposure calculation process from the aperture value obtained by the expression (1).

  The aperture value for the detected zoom position is obtained by linear interpolation according to the following equation (1). However, the present invention is not limited to this, and each zoom position and the aperture value corresponding to these zoom positions are determined. It is also possible to obtain an approximate expression for the aperture value, and obtain the aperture value for the detected zoom position using the obtained approximate expression.

As shown in FIG. 3, when the zoom position when performing the exposure correction calculation process is the position of the arrow in FIG. 3, the coefficient α is α = 0.4. Therefore, the aperture value at this time is Av = Av ₂ + (Av ₃ −Av ₂ ) × 0.4 = 2.90 + (3.05-2.90) × 0.4 = 2. 96. If the zoom position at the time of exposure calculation process is a Z _2, the aperture value in this case is 2.90. Accordingly, exposure calculation unit 51, the determined aperture value, zoom position is subtracted aperture in Z _2, obtains the correction value of the aperture value (0.06). Incidentally, when the zoom position at the time of exposure calculation processing is the position shown in Figure 3 in Z ₁ is the exposure calculating section 51, the determined aperture value, that the zoom position is subtracted aperture at the position indicated by Z ₁ The aperture value correction value is obtained.

  After obtaining the aperture value correction value, the exposure calculation unit 51 uses the aperture value correction value to obtain the shutter speed and imaging sensitivity correction values. The exposure calculation unit 51 corrects the exposure condition obtained in the exposure calculation process using the correction value obtained in the exposure correction calculation process. The exposure calculation unit 51 writes the corrected exposure condition in the work memory 42.

  When the correction value is obtained by the exposure correction calculation process, the exposure calculation unit 51 reads the exposure condition obtained by the exposure calculation process from the work memory 42. Then, the exposure calculation unit 51 corrects the read exposure condition using the obtained correction value.

  When the exposure condition is corrected, the CPU 40 reads the aperture value table 53 stored in the built-in memory 41. The CPU 40 reads the aperture value associated with each of the calculated aperture value and the zoom position from the aperture value table 53. The CPU 40 outputs a drive signal to the aperture drive unit 20. In response to this, the diaphragm drive unit 20 operates the diaphragm 46 so that the read aperture diameter is obtained. At the same time, the CPU 40 adjusts the shooting sensitivity of the image sensor 16 via the TG 21. In addition, when the release button 43 is operated, the CPU 40 causes the TG 21 to execute accumulation and readout of signal charges with respect to each pixel of the image sensor 16 based on the shutter speed obtained by the exposure calculation process described above. Output a control signal.

  For example, if the focus adjustment method in the electronic camera 10 is a contrast detection method, the focus evaluation unit 52 evaluates the focus evaluation value obtained when the focus lens is moved minutely, and obtains the position of the focus lens with the best focus. . Further, when the focus adjustment method is not the contrast detection method but the phase difference detection method, the focus evaluation unit 52 evaluates the interval between the two images formed by dividing the two-divided light and focuses the focus. Find the position of the focus lens that best matches.

  Next, the flow of processing during moving image shooting will be described based on the flowchart of FIG.

  Step S101 is processing for determining whether or not to start image acquisition. For example, when the release button 43 is operated, this operation signal is input to the CPU 40. Depending on whether or not this operation signal is input, the CPU 40 determines whether or not to start image acquisition. For example, when the operation signal described above is input, the CPU 40 sets the result of the determination process in step S101 to Yes. In this case, the process proceeds to step S102. On the other hand, when the above-described operation signal is not input, the CPU 40 sets the result of the determination process in step S101 to No. In this case, the process of the flowchart in FIG. 4 ends. Note that it is not necessary to start moving image capturing by operating the release button 43. For example, an operation button for moving image shooting is provided separately from the release button 43, and moving image shooting is performed when the operation button for moving image shooting is operated. It is also possible to do so. In this case, as the determination process in step S101, the CPU 40 may determine whether or not an operation button for moving image shooting has been operated.

  Step S102 is photometry processing. The CPU 40 operates the photometric sensor 30. Thereby, photometric processing is performed. The detection signal detected by the photometric sensor 30 is input to the CPU 40. The CPU 40 obtains the subject brightness using the detection signal from the photometric sensor 30.

  Step S103 is exposure calculation processing. The CPU 40 obtains the luminous intensity from the subject luminance obtained in step S102 and the set photographing sensitivity. Then, the CPU 40 obtains the aperture value and the shutter speed so that the obtained light intensity and the exposure value are equal. In this way, the exposure calculation is executed and the exposure condition is determined. The obtained exposure conditions are written in the work memory 42. The CPU 40 performs exposure control based on the determined exposure condition.

  Step S104 is an imaging process. The CPU 40 performs an imaging process using the exposure condition obtained by performing the process of step S103. Thereby, the frame image which comprises a moving image is acquired. The acquired frame image is subjected to image processing by the image processing unit 26 and then output to the display control unit 27. The display control unit 27 displays the input frame image on the display unit 28.

  Step S105 is processing for determining whether or not to perform exposure calculation processing. As described above, the exposure calculation process is executed with a time interval of 6 VD. The CPU 40 includes a counter (not shown). When the count number of the output vertical synchronization signal is 6, the CPU 40 determines that it is time to perform the exposure calculation process. That is, the CPU 40 sets the result of the determination process in step S105 to Yes. In this case, the process proceeds to step S106. On the other hand, if the count number of the output vertical synchronization signal is less than 6, the CPU 40 determines that it is not time to perform the exposure calculation process. That is, the CPU 40 sets the result of the determination process in step S105 to No. In this case, the process proceeds to step S110.

  Step S106 is photometry processing. The process in step S106 is the same as the process in step S102.

  Step S107 is exposure calculation processing. The process in step S107 is the same as that in step S103. Thereby, a new exposure condition is calculated.

  Step S108 is an imaging process. The process of step S108 is the same process as step S104. By performing the process of step S108, a new frame image is acquired. The frame image obtained in step S108 is subjected to image processing by the image processing unit 26 and then output to the display control unit 27. The display control unit 27 displays the input frame image on the display unit 28 as a newly displayed image.

  Step S109 is processing to determine whether or not to end image acquisition. When the release button 43 is operated again, an operation signal is input to the CPU 40. When this operation signal is input, the CPU 40 ends the moving image shooting. Therefore, the CPU 40 determines whether or not to end the image acquisition depending on whether or not this operation signal is input. For example, when the operation signal described above is input again, the CPU 40 sets the result of the determination process in step S109 to Yes. In this case, the process of the flowchart shown in FIG. On the other hand, when the operation signal described above is not input again, the CPU 40 sets the result of the determination process in step S109 to No. In this case, the process proceeds to step S105. Therefore, when the result of the determination process in step S109 is No, moving image shooting is continued.

  If the determination result in step S105 described above is No, in other words, if the exposure calculation process is not executed, the process proceeds to step S110.

  Step S110 is a process for determining whether or not to execute the exposure correction calculation process. As described above, the CPU 40 executes the exposure correction calculation process with a time interval of 1 VD. The time interval of 1 VD coincides with the output interval of the vertical synchronization signal. Therefore, the CPU 40 refers to the count number of the counter described above, and executes the determination process of step S110 depending on whether the count number of the counter is incremented. When the count number of the counter is incremented, the CPU 40 determines that the exposure correction calculation process is to be executed, and sets the result of the determination process in step S110 to Yes. In this case, the process proceeds to step S111. On the other hand, when the count number of the counter is not incremented, the CPU 40 determines not to execute the exposure correction calculation process, and sets the result of the determination process in step S110 to No. In this case, the process proceeds to step S109.

  Step S111 is processing to determine whether or not there is a zoom operation. When the user operates the operation unit 44 to change the optical zoom magnification, an operation signal is output from the operation unit 44 to the CPU 40. If the CPU 40 determines from the input operation signal that a signal indicating a change in the optical zoom magnification has been input, the CPU 40 sets the determination processing result in step S111 to Yes. In this case, the process proceeds to step S112.

  On the other hand, if the CPU 40 determines that the signal indicating the change of the optical zoom magnification is not input, the CPU 40 sets the result of the determination process in step S111 to No. In this case, the process proceeds to step S108. If the result of the determination process in step S111 is No, the exposure correction calculation process in step S112 is not executed. Therefore, the CPU 40 executes the imaging process using the exposure condition obtained in the exposure calculation process in step S103 or the exposure calculation process in step S107 as the imaging process in step S108.

  In step S111, it is determined whether or not a signal indicating a change in optical zoom magnification is input from the operation unit 44. If an operation signal is input from the operation unit 44, the CPU 40 indicates a flag indicating that. Is written in the work memory 42. Therefore, the CPU 40 can execute the determination process in step S111 after referring to whether or not the work memory 42 has a flag.

  Step S112 is exposure correction calculation processing. The CPU 40 obtains the zoom position with reference to the number of drive pulse signals of the stepping motor constituting the lens drive unit 19. Then, the CPU 40 reads the aperture value table 53 stored in the built-in memory 41. The CPU 40 refers to the read aperture value table 53 and the obtained zoom position, and obtains the aperture value (Av value) using the above-described equation (1). The CPU 40 calculates a correction value for the aperture value by subtracting the aperture value obtained in the exposure calculation process from the obtained aperture value. The CPU 40 calculates the shutter speed and photographing sensitivity correction values based on the calculated aperture value correction values. Then, the CPU 40 reads the exposure condition from the work memory 42 and corrects the read exposure condition using the obtained correction value. When step S112 ends, the process proceeds to step S108. Therefore, in the imaging process of step S108 executed after the process of step S112 is performed, the CPU 40 performs the imaging process using the corrected exposure condition.

  FIG. 5 is a timing chart when a moving image is captured without changing the optical zoom magnification. When shooting a moving image, the CPU 40 performs an exposure calculation process with a time interval of 6 VD. When the exposure calculation process is started, the CPU 40 drives the photometric sensor 30 to start the photometric process. The photometric process includes a light receiving process (“light reception” in FIG. 5) in the photometric sensor 30, a process of reading signal charges based on the received light (“read” in FIG. 5), and an AE evaluation value from a voltage signal based on the read signal charges. Each process of the process of calculating ("Calculation" in FIG. 5). The CPU 40 executes these processes with a time interval of 1 VD. After this photometry processing, the CPU 40 executes photometry calculation processing and exposure calculation processing. Here, in FIG. 5, Tv_n−1 [0], Tv_n [0], and Tv_n + 1 [0] are shutter speeds obtained in the exposure calculation process that is executed with a time interval of 6 VD. In FIG. 5, Sv_n−1 [0], Sv_n [0], and Tv_n + 1 [0] are imaging sensitivities obtained in the exposure calculation process with a time interval of 6 VD.

  As described above, in moving image shooting, imaging processing is executed with a time interval of 1 VD. Therefore, when the optical zoom magnification is not changed, the CPU 40 executes the imaging process with a time interval of 1 VD using the exposure condition obtained by the exposure calculation process. Then, when 6 VD has elapsed, the CPU 40 newly performs an exposure calculation process. Therefore, when the optical zoom magnification is not changed during shooting of a moving image, the CPU 40 executes an imaging process using the exposure condition calculated every 6 VD time interval with a 1 VD time interval.

  FIG. 6 is a timing chart when the optical zoom magnification is changed in moving image shooting. Even when the optical zoom magnification is changed in moving image shooting, the CPU 40 performs the exposure calculation process with a time interval of 6 VD, as in the case where the optical zoom magnification is not changed. As described above, when the optical zoom magnification is changed in moving image shooting, the CPU 40 executes the exposure correction calculation process with a time interval of 1 VD.

  For example, consider the case where the shutter speed (Tv value) is set to Tv_n−1 [0] and the photographing sensitivity (Sv value) is set to Sv_n−1 [0] by the exposure calculation process. At this time, when the optical zoom magnification is not changed, the CPU 40 executes the imaging process using the calculated exposure condition with a time interval of 1 VD until a new exposure calculation process is executed. For example, when the optical zoom magnification is changed at the timing indicated by the arrow in FIG. 6 while shooting a moving image, the CPU 40 executes an exposure correction calculation process in accordance with the output of the vertical synchronization signal. By this exposure correction calculation processing, for example, the shutter speed is corrected to Tv_n−1 [4]. Further, the photographing sensitivity is corrected to Sv_N−1 [4]. Further, every time the time interval of 1 VD elapses, the CPU 40 executes an exposure correction calculation process. In FIG. 6, the shutter speed corrected by the exposure correction calculation process is indicated by Tv_n-1 [5], and the photographing sensitivity is indicated by Sv_n-1 [5].

  When the time interval of 6 VD elapses after the exposure calculation process is executed, the CPU 40 newly executes the exposure calculation process. If the zoom magnification is changed after the exposure calculation process, the CPU 40 executes the exposure correction calculation process every time a time interval of 1 VD elapses. As described above, the CPU 40 corrects the exposure condition obtained by the exposure calculation process executed with a time interval of 6 VD, for example, every time the time interval of 1 VD elapses. In this exposure correction calculation processing, the CPU 40 calculates a change amount (correction value) of the aperture value based on the variation amount of the optical zoom magnification using the aperture value table, and then calculates the shutter speed and the shutter speed based on the change amount of the aperture value. The (correction value) of the shooting sensitivity is obtained. The correction value obtained by the exposure correction calculation process is a correction value for the exposure condition obtained by the exposure calculation process described above.

  In the description in FIG. 6, the symbols Tv_n [1], Tv_n [2], Tv_n [3], Tv_n [4], and Tv_n [5] indicate the shutter speed Tv_n [0] obtained by the exposure calculation process. The shutter speed corrected using each of the correction values obtained by the exposure correction calculation process executed with a time interval of 1 VD is shown. Similarly, the symbols Tv_n + 1 [1], Tv_n + 1 [2], Tv_n + 1 [3], Tv_n + 1 [4], and Tv_n + 1 [5] set the shutter speed Tv_n + 1 [0] obtained by the exposure calculation process to a time interval of 1VD. The shutter speed corrected using each of the correction values obtained by the exposure correction calculation process executed in the sky is shown.

  In addition, in the description in FIG. 6, symbols Sv_n [1], Sv_n [2], Sv_n [3], Sv_n [4], and Sv_n [5] indicate the shutter speed Sv_n [0] obtained by the exposure calculation process. The imaging sensitivity corrected using each of the correction values obtained by the exposure correction calculation process executed with a time interval of 1 VD is shown. Similarly, the codes Sv_n + 1 [1], Sv_n + 1 [2], Sv_n + 1 [3], Sv_n + 1 [4], and Sv_n + 1 [5] set the photographing sensitivity Sv_n + 1 [0] obtained by the exposure calculation process to the time interval of 1VD. The photographing sensitivity corrected using each of the correction values obtained by the exposure correction calculation process executed at an interval is shown.

  Therefore, in the method of calculating the exposure condition by performing the exposure calculation process for one imaging process, the load related to the calculation process is large, but in the method of calculating the correction value by the exposure correction calculation process described above, the calculated correction is performed. It is only necessary to correct the exposure condition obtained in the exposure calculation process using the value, and the load related to the calculation process can be reduced.

  In addition, conventionally, since the exposure condition obtained in the exposure calculation process executed at a predetermined cycle is used in a plurality of imaging processes, the exposure condition obtained in the exposure calculation process and the time of each imaging process The exposure condition becomes farther away as the number of imaging processes increases. Therefore, there is a large difference in exposure conditions between the image obtained by the imaging process using the exposure condition obtained in the next exposure calculation process and the image obtained by the imaging process immediately before performing the exposure calculation process. When these images are displayed, image flickering occurs.

  In the present embodiment, exposure correction calculation processing is performed at a predetermined time period such as a time interval of 1 VD during exposure calculation processing executed with a time interval of 6 VD, and imaging processing is performed using the corrected exposure conditions. Run. Since this exposure correction calculation process corrects (adjusts) the exposure condition in each imaging process to an appropriate exposure condition, it is executed immediately before the exposure condition determined by the next exposure calculation process and this exposure calculation process. The difference from the exposure condition corrected by the exposure correction calculation process can be reduced. Therefore, when an image obtained by the imaging process is displayed, it is possible to suppress the occurrence of image flickering due to the difference in exposure conditions.

  In this embodiment, the case where moving image shooting is performed is described as an example. However, the present invention can also be applied to a case where a through image obtained in a shooting standby state is acquired. In the case of acquiring a through image, the CPU 40 sets the operation mode of the electronic camera 10 to the moving image shooting mode or the still image shooting mode as a determination process in step S101 of the flowchart shown in FIG. It is determined whether or not the release button is not operated. In this case, when it is determined that the operation mode of the electronic camera 10 is set to the moving image shooting mode or the still image shooting mode, and the release button for starting the shooting is not operated, the CPU 40 proceeds to step S101. The result of the determination process may be set to Yes.

  In addition, in the determination process in step S109 of the flowchart illustrated in FIG. 4, the operation mode of the electronic camera 10 is set to the setting mode for changing the setting of the electronic camera 10 or the acquired image from the moving image shooting mode or the still image shooting mode described above. It is determined whether or not the playback mode has been changed to playback. In this case, the CPU 40 determines that the operation mode of the electronic camera 10 has been changed from the moving image shooting mode or the still image shooting mode described above to a setting mode for changing the setting of the electronic camera 10 or a playback mode for reproducing the acquired image. In such a case, the result of the determination process in step S109 may be Yes.

  In this embodiment, a lens driving unit including a stepping motor is taken as an example, and the zoom position is calculated based on the count value of the number of driving steps when driving the stepping motor. However, it is necessary to limit to this. For example, a detection sensor for detecting the position of the zoom lens may be provided, and the zoom position may be obtained based on a detection signal from the detection sensor.

  In the present embodiment, details of the speed when changing the optical zoom magnification are omitted. The speed at which the optical zoom magnification is changed may be a constant speed, or may be variable in multiple stages such as two stages. For example, in the form in which the speed when changing the optical zoom magnification is two steps, for example, if the optical zoom magnification is changed at high speed, the exposure calculation process may not be able to follow the optical zoom magnification. Therefore, for example, when the optical zoom magnification is changed at high speed, the present invention can be used.

  In this embodiment, the exposure correction calculation process is performed at a time interval of 1 VD with respect to the exposure calculation process executed at a time period of 6 VD. However, the present invention is not limited to this. It is also possible to perform exposure calculation processing at intervals. For example, when the speed at which the optical zoom magnification is changed is high, the change in the exposure condition is also large. Therefore, for example, exposure correction calculation processing is performed at a time interval of 2 VD. Since it is small, exposure correction calculation processing is performed at time intervals of 1 VD.

  DESCRIPTION OF SYMBOLS 10 ... Electronic camera, 15 ... Imaging optical system, 16 ... Imaging element, 19 ... Lens drive part, 20 ... Aperture drive part, 30 ... Photometric sensor, 40 ... CPU, 41 ... Built-in memory, 46 ... Aperture, 51 ... Exposure calculation , 52... Focus evaluation unit, 53... Aperture value table

Claims (9)

An optical system capable of changing the optical magnification by moving a plurality of lenses in the optical axis direction;
An aperture having an aperture through which subject light captured by the optical system passes, and the amount of the subject light can be adjusted by changing the aperture diameter of the aperture; and
A detection unit for detecting the position of the optical system;
An exposure calculation unit for calculating exposure conditions at the time of image acquisition;
Based on the position of the optical system and the aperture diameter of the diaphragm detected by the detection unit when the optical magnification of the optical system is changed in the process of continuously acquiring the plurality of images. A correction unit for correcting the exposure condition;
An imaging apparatus comprising: The imaging device according to claim 1,
The positions of the diaphragms associated with the positions of the different optical systems, the aperture diameters of the different diaphragms, the positions of the different optical systems and the aperture diameters of the different diaphragms, respectively. It has a storage unit that stores table data that summarizes aperture values.
The correction unit calculates a correction value of the aperture value when the optical magnification of the optical system is changed using the position of the optical system, the aperture diameter of the aperture, and the table data. An imaging apparatus, wherein the exposure condition is corrected based on a correction value of the aperture value. The imaging device according to claim 2,
The correction unit includes the position of the optical system in a range including the position of the optical system detected by the detection unit among the positions of the plurality of different optical systems, and the position corresponding to the position of the optical system. The aperture diameter of the aperture is read from the table data, the aperture value of the aperture with respect to the position of the optical system detected by the detection unit is obtained, and then obtained by the exposure calculation unit from the obtained aperture value of the aperture. In addition, the correction value of the aperture value is obtained by subtracting the aperture value of the aperture. The imaging device according to claim 3.
The correction unit performs linear interpolation using the position of the optical system in a range including the position of the optical system detected by the detection unit, and the aperture diameter of the diaphragm corresponding to the position of the optical system, An imaging apparatus, wherein an aperture value of the aperture at a position of the optical system detected by the detection unit is obtained. In the imaging device according to any one of claims 1 to 4,
The exposure calculation unit calculates the exposure condition at a first time interval when acquiring the plurality of images continuously,
The imaging apparatus corrects the exposure condition at a second time interval that is different from the first time interval and shorter than the first time interval. The imaging apparatus according to claim 5,
There are multiple speeds for changing the optical magnification of the optical system,
The imaging device, wherein the correction unit changes the second time interval according to a speed at which the optical magnification of the optical system is changed. In the imaging device according to claim 5 or 6,
An image sensor for receiving subject light captured by the optical system;
An exposure control unit that performs exposure control based on the exposure condition calculated by the exposure calculation unit or the exposure condition corrected by the correction unit;
An imaging control unit for controlling the operation of the imaging element;
An imaging apparatus comprising: The imaging apparatus according to claim 7,
The imaging control unit is capable of acquiring a plurality of images continuously by controlling the operation of the imaging element at predetermined time intervals.
The imaging apparatus according to claim 1, wherein the first time interval and the second time interval are an integral multiple of the predetermined time interval. In the imaging device according to any one of claims 1 to 8,
A display unit for displaying the image;
An imaging apparatus, further comprising: a display control unit that causes the display unit to display the plurality of images continuously acquired by the imaging element.

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