Imaging device

Abstract

To provide an imaging apparatus capable of capturing a natural moving image continuously even if brightness changes.SOLUTION: In the imaging apparatus whose exposure condition is set on the basis of the characteristic of a transmittance control element, a first exposure condition range is calculated on the basis of light measurement by the imaging apparatus. It is determined whether the calculated first exposure condition range is included in a second exposure condition range to which a control range acquired by the transmittance control element is applicable. If the calculated first exposure condition range is not included in the second exposure condition range, the exposure condition of the imaging apparatus is changed such that the first exposure condition range is included in the second exposure condition range.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an imaging device, and more particularly to an imaging device that captures moving images. [Background technology]

[0002] BACKGROUND ART Techniques for controlling exposure using a transmittance control element such as a variable neutral density filter (ND filter) are known (Patent Documents 1 to 3, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-191310 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-62466 [Patent Document 3] International Publication No. 2013 / 031429 Summary of the Invention

[0004] One embodiment of the technique of the present disclosure provides an imaging device that can capture natural moving images continuously even when the brightness changes. [Means for solving the problem]

[0005] (1) An imaging device in which exposure conditions are set based on the characteristics of a transmittance control element, comprising a processor, wherein the processor calculates a first exposure condition range based on the photometry of the imaging device, and if the first exposure condition range is not included in a second exposure condition range to which the control range acquired by the transmittance control element can be applied, changes the exposure conditions of the imaging device so that the calculated first exposure condition range is included in the second exposure condition range.

[0006] (2) The imaging device of (1), wherein the processor determines imaging scene information based on photometry of the imaging device, and calculates a first exposure condition range based on the determined imaging scene information.

[0007] (3) The imaging device of (1) or (2), wherein the processor controls exposure using the transmittance control element in the second exposure condition range during imaging.

[0008] (4) An imaging device according to (3), wherein, during imaging, if a third exposure condition range calculated based on the photometry of the imaging device differs from the first exposure condition range, the processor changes the exposure conditions of the imaging device so that the second exposure condition range is included in the third exposure condition range.

[0009] (5) The imaging device according to any one of (1) to (4), wherein the exposure conditions are an aperture control amount, a shutter speed control amount, and a sensitivity control amount.

[0010] (6) The imaging device according to (5), wherein the processor determines the exposure control mode, and if the exposure control mode is the aperture priority mode, fixes the aperture control amount and sets the exposure conditions.

[0011] (7) The imaging device according to (5), wherein the processor determines the exposure control mode, and if the exposure control mode is the shutter speed priority mode, fixes the shutter speed control amount and sets the exposure conditions.

[0012] (8) The imaging device of (5), wherein the processor determines the exposure control mode, and if the exposure control mode is manual, fixes the aperture control amount and the shutter speed control amount to set the exposure conditions.

[0013] (9) The imaging device of (5), wherein the processor determines the exposure control mode, and when the exposure control mode is the auto mode, sets the transmittance control element to the median value of the movable range.

[0014] (10) The imaging device of (9), wherein the processor changes the aperture control amount, shutter speed control amount, and sensitivity control amount in a predetermined order of priority when the transmittance control element is out of a settable range during imaging.

[0015] (11) The imaging device of (10), wherein the order of priority is the shutter speed control amount in the range from the maximum value to half the maximum value, the sensitivity control amount, the shutter speed control amount at half the maximum value, and the aperture control amount.

[0016] (12) An imaging device according to any one of (1) to (11), wherein the processor measures the fluctuation range of the exposure when capturing a video, records information on the measured fluctuation range of the exposure in memory, and sets the first exposure condition range based on the historical information on the fluctuation range of the exposure recorded in the memory.

[0017] (13) An imaging device according to any one of (1) to (11), wherein the processor acquires in advance information on the expected fluctuation range of exposure when capturing a video, and sets the first exposure condition range based on the acquired information on the fluctuation range of exposure.

[0018] (14) An imaging device according to any one of (1) to (11), wherein the processor acquires information on the fluctuation range of the exposure of the area where the video is captured in advance, and sets the first exposure condition range based on the acquired information on the fluctuation range of the exposure. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an imaging device; [Figure 2] Block diagram of exposure control functions [Figure 3] FIG. 10 is a diagram showing an example of region division. [Figure 4] Conceptual diagram of determining whether correction is necessary [Figure 5] Conceptual diagram of determining whether correction is necessary [Figure 6] Conceptual diagram of variable ND filter setting correction [Figure 7] A flowchart showing a procedure for setting an exposure control amount when starting imaging. [Figure 8] Flowchart showing the procedure for exposure control during imaging [Figure 9] 1 is a flowchart showing the procedure for exposure control during image capture when the exposure control mode is auto mode. [Figure 10] 10 is a flowchart showing the procedure for setting the exposure control amount. [Figure 11] Conceptual diagram of calculation of estimated exposure fluctuation range [Figure 12] FIG. 10 is a diagram showing an example of a margin added to an estimated exposure change amount; [Figure 13] FIG. 1 is a diagram showing an example of the relationship between exposure and scene. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] [First embodiment] When shooting video, it is undesirable for the depth of field, sense of motion, and graininess to change during shooting, except when aiming for a special expression. Generally, depth of field changes with aperture value, sense of motion with shutter speed, and graininess with imaging sensitivity. By using a transmittance control element such as a variable ND filter, it is possible to control exposure without changing aperture value, shutter speed, or imaging sensitivity during shooting. This makes it possible to capture natural-looking video continuously even when the brightness changes.

[0022] However, the movable range of the transmittance control element is limited. Therefore, if the transmittance control element is set near the upper or lower limit of its movable range when starting to capture a moving image, there is a risk that the exposure cannot be controlled by the transmittance control element alone during capture. On the other hand, if the transmittance control element is forcibly set to the middle value of its movable range, it will be impossible to capture a moving image under the exposure conditions (aperture value, shutter speed, and imaging sensitivity) desired by the user.

[0023] In this embodiment, an imaging device is provided that can continuously capture natural moving images even when the brightness changes, while maintaining the exposure conditions set by the user as much as possible.

[0024] [Device configuration] FIG. 1 is a diagram showing a schematic configuration of an imaging device.

[0025] As shown in the figure, the imaging device 1 of this embodiment mainly includes an imaging lens 10, an imaging element 20, an imaging element driving unit 22, an analog signal processing unit 24, an ADC (Analog to Digital Converter) 26, a main memory unit 28, a digital signal processing unit 30, an auxiliary memory unit 32, a display unit 34, an operation unit 36, and a system control unit 40.

[0026] The imaging lens 10 mainly includes a lens 11, an aperture 12, a variable ND filter 13, a lens driver 14, an aperture driver 15, and an ND filter driver 16. For convenience, only one lens 11 is shown in Fig. 1, but the imaging lens 10 actually includes multiple lenses.

[0027] The imaging lens 10 is, for example, a zoom lens. The imaging lens 10 zooms by moving the zoom lens group back and forth along the optical axis. The imaging lens 10 also has a focus adjustment mechanism, and the focus is adjusted by moving the focus lens group back and forth along the optical axis. A lens driver 14 moves the zoom lens group and the focus lens group back and forth along the optical axis.

[0028] The diaphragm 12 is configured as, for example, an iris diaphragm. The diaphragm 12 is disposed in the optical path of the imaging lens 10 and adjusts the amount of light passing through the imaging lens 10. The diaphragm 12 is driven by a diaphragm driver 15 to change the amount of opening.

[0029] The variable ND filter 13 is disposed in the optical path of the imaging lens 10 and uniformly reduces the amount of light passing through the imaging lens 10. The variable ND filter 13 is an ND filter with a variable rate of reduction in the amount of light. The imaging device 1 of this embodiment uses an electronic variable ND filter 13. The rate of reduction in the amount of light of an electronic variable ND filter changes depending on the voltage applied to it. The imaging device 1 of this embodiment uses, as an example, a variable ND filter 13 whose rate of reduction in the amount of light changes in the range from 1 / 4 to 1 / 128. The variable ND filter 13 is an example of a transmittance control element. The variable ND filter 13 is driven by the ND filter driver 16 to change the rate of reduction in the amount of light.

[0030] The image sensor 20 is configured as a color area image sensor. The image sensor may be, for example, a CMOS (Complementary Metal-Oxide Semiconductor) type or a CCD (Charged Coupled Device) type image sensor having a predetermined color filter array (e.g., a Bayer array). The image sensor 20 operates by being driven by an image sensor driver 22. The imaging device 1 adjusts the exposure time (shutter speed) by electronically controlling the on / off of the image sensor 20 (so-called electronic shutter function).

[0031] The analog signal processing unit 24 performs predetermined signal processing on the analog image signal output from the imaging element 20. The analog signal processing unit 24 includes a sample-and-hold circuit, a color separation circuit, an AGC (Automatic Gain Control) circuit, etc. The AGC circuit functions as a sensitivity adjustment unit that adjusts the imaging sensitivity (ISO sensitivity (ISO: International Organization for Standardization)).

[0032] The ADC 26 converts the analog image signal that has been subjected to predetermined signal processing by the analog signal processing unit 24 into a digital image signal.

[0033] When the imaging element 20 is configured as a CMOS image sensor, the imaging element driver 22, the analog signal processor 24, and the ADC 26 are often included in the imaging element 20. When the imaging element 20 is configured as a CMOS image sensor, a digital image sensor signal processor is often provided instead of the analog signal processor 24.

[0034] When the imaging element 20 is configured as a CMOS image sensor including an ADC and a digital image sensor signal processing unit, the imaging element 20 outputs a signal from each pixel as follows: The signal from each pixel is amplified by an analog amplifier provided for each pixel or for each set of pixels, and then read out row by row and supplied to the ADC. The ADC converts the supplied signal from each pixel into a digital signal and supplies it to the image sensor signal processing unit. The image sensor signal processing unit performs various signal processing such as digital correlated double sampling, digital gain processing, and correction processing on the supplied digital signal from each pixel. The signal that has undergone various signal processing in the signal processing unit is output from the imaging element 20.

[0035] The main memory unit 28 is used as a temporary storage area for data. The image signal output from the imaging element 20 passes through the analog signal processor 24 and the ADC 26 and is stored in the main memory unit 28 for each frame.

[0036] The digital signal processing unit 30 generates image data by performing signal processing such as offset processing, gamma correction processing, demosaic processing, and RGB / YCrCb conversion processing on the digitally converted image signal. The digital signal processing unit 30 is formed by, for example, a microprocessor.

[0037] The auxiliary storage unit 32 mainly stores image data obtained by capturing images. The auxiliary storage unit 32 is composed of an internal memory and / or an external memory. The internal memory is a memory built into the main body of the imaging device 1. The internal memory is composed of, for example, a non-volatile semiconductor memory. The external memory is composed of, for example, a memory card, which is inserted into a card slot provided in the main body of the imaging device.

[0038] The display unit 34 is used to play back captured images and to display live view images during image capture. It is also used as a setting screen when configuring various settings. The display unit 34 is configured with a display such as an LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Diode).

[0039] The operation unit 36 ​​includes various operation members for operating the imaging device 1. The operation members include an operation member (power button) for turning the imaging device 1 on and off, an operation member (record button) for instructing the start and end of imaging, and operation members for making various settings. The operation members for making various settings include, for example, an operation member for setting the exposure control mode, an operation member for setting the aperture value, an operation member for setting the shutter speed, and an operation member for setting the imaging sensitivity. The operation member for setting the exposure control mode is, for example, a mode dial. The exposure control modes include, for example, auto mode, aperture priority mode, shutter speed priority mode, and manual mode. Auto mode is a mode in which the aperture value, shutter speed, and imaging sensitivity are automatically set. Aperture priority mode is a mode in which the shutter speed and imaging sensitivity are automatically set according to the set aperture value. Shutter speed priority mode is a mode in which the aperture value and imaging sensitivity are automatically set according to the set shutter speed. Manual mode is a mode in which the aperture value and shutter speed are manually set. The operation member for setting the aperture value is, for example, an aperture ring. The operation member for setting the shutter speed is, for example, a shutter speed dial. The operation member for setting the image sensitivity is, for example, a image sensitivity dial. These settings can also be configured to be set on the screen using the display unit 34 and operation members such as a cross key. The operation unit 36 ​​outputs signals to the system control unit 40 in response to the operation of each operation member.

[0040] The system control unit 40 controls the operation of each unit of the imaging device 1 and centrally controls the overall operation of the imaging device 1. The system control unit 40 also performs processes such as calculating physical quantities required for control. The system control unit 40 is configured, for example, by a microcomputer equipped with a processor and memory. The processor is configured, for example, by a CPU (Central Processing Unit) or the like. The memory is configured, for example, by a RAM (Random Access Memory) and a ROM (Read Only Memory) or the like. The memory stores programs executed by the processor and various data.

[0041] The control performed by the system control unit 40 includes exposure control. In the imaging device 1 of this embodiment, exposure is controlled by the aperture 12, shutter speed, imaging sensitivity, and variable ND filter 13. Below, we will explain the exposure control performed when capturing a moving image with the imaging device 1 of this embodiment.

[0042] FIG. 2 is a block diagram of functions related to exposure control.

[0043] As shown in the figure, the system control unit 40 functions as an exposure control mode discriminator 40A, a photometry unit 40B, an exposure control amount setting unit 40C, an exposure change amount estimator 40D, and an exposure control amount corrector 40E with respect to exposure control.

[0044] The exposure control mode discrimination unit 40A discriminates the currently set exposure control mode. The exposure control mode discrimination unit 40A discriminates the exposure control mode based on information from the operation unit 36. Specifically, the exposure control mode discrimination unit 40A discriminates the currently set exposure control mode (auto mode, aperture priority mode, shutter speed priority mode, manual mode, etc.) based on the setting of the mode dial.

[0045] The photometry unit 40B measures the brightness of the subject based on the image signal output from the image sensor 20. The photometry unit 40B measures the brightness of the subject and calculates the amount of exposure. The amount of exposure is calculated, for example, as an EV (Exposure Value). In the image sensor 1 of this embodiment, the light receiving surface of the image sensor 20 is divided into a plurality of regions, and photometry is performed for each region to calculate the amount of exposure. FIG. 3 is a diagram showing an example of region division. As shown in the figure, in the image sensor of this embodiment, the light receiving surface 20A of the image sensor 20 is equally divided into 8×8 regions a11 to a88.

[0046] The exposure control amount setting unit 40C sets the exposure control amount. That is, it sets the aperture value, shutter speed, imaging sensitivity, and light intensity reduction rate. In particular, the aperture value, shutter speed, and imaging sensitivity are set as exposure conditions. The aperture value is an example of an aperture control amount. The shutter speed is an example of a shutter speed control amount. The imaging sensitivity is an example of a sensitivity control amount. The exposure control amount setting unit 40C sets the exposure control amount to achieve the desired brightness based on the photometry results of the photometry unit 40B. For example, the exposure control amount setting unit 40C weights the photometry results of each area to determine the overall exposure amount, and sets the exposure control amount to achieve the desired brightness based on the determined overall exposure amount. The desired brightness is, for example, a brightness that results in appropriate exposure. Normally, each exposure control amount is set to achieve appropriate exposure. Furthermore, for example, if exposure correction or the like is performed, each exposure control amount is set to achieve the corrected exposure.

[0047] When setting the exposure control amount, the exposure control amount setting unit 40C sets each exposure control amount according to the currently set exposure control mode. In auto mode, the variable ND filter 13 is set to the median value of its movable range and each exposure control amount is set. In aperture priority mode, the aperture value is fixed and each exposure control amount is set. In shutter speed priority mode, the shutter speed is fixed and each exposure control amount is set. In manual mode, the aperture value and shutter speed are fixed and each exposure control amount is set. In each mode, the exposure control amount is set according to a predetermined standard to achieve the desired brightness. For example, it is set according to a program diagram or the like.

[0048] The exposure change estimating unit 40D estimates the exposure change of the scene to be captured. The exposure change estimating unit 40D estimates the exposure change based on the photometry results (exposure of each area a11 to a88) of the photometry unit 40B. In this embodiment, the exposure change is estimated as follows: First, exposure information for each area a11 to a88 is obtained. Next, the darkest area and the brightest area are identified based on the obtained exposure information for each area a11 to a88. Next, an exposure range that covers the identified darkest area to the brightest area is obtained. The obtained range is used as the estimated exposure change. In this case, for example, if the exposure of the darkest area is 10 EV and the exposure of the brightest area is 15 EV, the range of 10 EV to 15 EV is calculated as the estimated exposure change.

[0049] The exposure control amount corrector 40E corrects the exposure control amounts set by the exposure control amount setting unit 40C as necessary. The exposure control amount corrector 40E determines whether correction is necessary based on the characteristics of the variable ND filter 13, the setting value of the variable ND filter 13, the amount of exposure change estimated by the exposure change amount estimator 40D (estimated amount of exposure change), and the amount of exposure when the exposure control amount was set. Here, the characteristics of the variable ND filter 13 specifically refer to the control range of the variable ND filter 13. The control range of the variable ND filter 13 is specified as the movable range of the variable ND filter 13. The movable range of the variable ND filter 13 is what is called a movable width, and is the range of the light amount reduction rate that can be changed. In the case of the variable ND filter 13 of this embodiment, the movable range is between 1 / 4 and 1 / 128.

[0050] 4 and 5 are conceptual diagrams of determining whether correction is necessary. Fig. 4 shows an example of a case where correction is unnecessary, and Fig. 5 shows an example of a case where correction is necessary.

[0051] If the estimated exposure fluctuation range S is not included in the settable range R of the variable ND filter 13, the exposure control amount correction unit 40E determines that correction is necessary.

[0052] The estimated exposure fluctuation range S is the predicted fluctuation range of exposure when capturing a moving image. The estimated exposure fluctuation range S is calculated by using the exposure M when the exposure control amount is set as a reference, and determining an estimated exposure fluctuation range Sa on the darker side and an estimated exposure fluctuation range Sb on the brighter side. The exposure M when the exposure control amount is set represents the current brightness (exposure) of the subject.

[0053] The estimated exposure variation range S is calculated based on the estimated exposure change amount. For example, if the estimated exposure change amount is Amin to Amax (Amin is the minimum value of the estimated exposure change amount, and Amax is the maximum value of the estimated exposure change amount), the range from Amin to M becomes the estimated exposure variation range Sa on the darker side. Also, the range from M to Amax becomes the estimated exposure variation range Sb on the brighter side. The estimated exposure variation range S is an example of a first exposure condition range.

[0054] The settable range R of the variable ND filter 13 is the range in which the control range of the variable ND filter 13 can be applied. The settable range R of the variable ND filter 13 is calculated by using the current setting value N (currently set light intensity reduction rate) as a reference, and determining the settable range Ra in the direction of decreasing the reduction rate (in the direction of brightening) and the settable range Rb in the direction of increasing the reduction rate (in the direction of darkening). If the movable range of the variable ND filter 13 is 1 / 4 to 1 / 128, the settable range Ra in the direction of decreasing the reduction rate is the range from 1 / 4 to N, and the settable range Rb in the direction of increasing the reduction rate is the range from N to 1 / 128. The settable range R of the variable ND filter 13 is an example of a second exposure condition range.

[0055] 4, the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13. In this case, exposure control during imaging is possible using only the variable ND filter 13. Therefore, when the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13, the exposure control amount correction unit 40E determines that correction of the exposure control amount set by the exposure control amount setting unit 40C is not necessary.

[0056] On the other hand, in the example shown in Figure 5, the estimated exposure fluctuation range S exceeds the settable range R of the variable ND filter 13. In other words, the settable range Rb in the direction of increasing the rate of decrease is insufficient compared to the estimated exposure fluctuation range Sb on the brighter side. In this case, the variable ND filter 13 alone cannot follow the change in brightness. Therefore, in this case, the exposure control amount correction unit 40E determines that the exposure control amount set by the exposure control amount setting unit 40C needs to be corrected.

[0057] If it is determined that exposure control amount correction is necessary, exposure control amount corrector 40E corrects the exposure control amount so that estimated exposure fluctuation range S falls within settable range R of variable ND filter 13. In other words, the exposure control amount is corrected so that estimated exposure fluctuation range Sa on the darker side falls within settable range Ra in the direction that decreases the rate of decrease, and estimated exposure fluctuation range Sb on the brighter side falls within settable range Rb in the direction that increases the rate of decrease. Correction is performed, for example, using the following procedure.

[0058] First, the setting value of the variable ND filter 13 is corrected so that the estimated exposure fluctuation range is included in the settable range of the variable ND filter 13. In other words, the currently set reduction rate of the light amount is corrected.

[0059] 6 is a conceptual diagram of the correction of the variable ND filter settings, showing an example of correction from the state shown in FIG.

[0060] In the example shown in FIG. 5, the settable range Rb in the direction of increasing the reduction rate is insufficient relative to the estimated exposure fluctuation range Sb on the brighter side. Therefore, in this case, the setting value of the variable ND filter 13 is corrected in the direction of decreasing the reduction rate. In this case, it is preferable to use the minimum amount of correction. This allows the amount of correction to be reduced when correcting other exposure control variables. In other words, it is possible to maintain a state as close to the current exposure conditions as possible.

[0061] In the example shown in FIG. 6, the setting value of the variable ND filter 13 is corrected so that the estimated exposure fluctuation range Sb on the brighter side coincides with the settable range Rb in the direction in which the decrease rate increases.

[0062] After correcting the setting value of the variable ND filter 13, other exposure control variables are corrected. That is, since the setting value of the variable ND filter 13 changes due to the correction, the exposure conditions (aperture value, shutter speed, and imaging sensitivity) are changed so that the desired brightness is achieved under the new setting value (light reduction rate). At this time, each exposure control variable is corrected according to the currently set exposure control mode. That is, when the exposure control mode is set to aperture priority mode, exposure control variables other than aperture value are corrected. Also, when the exposure control mode is set to shutter speed priority mode, exposure control variables other than shutter speed are corrected. Also, when the exposure control mode is set to manual mode, exposure control variables other than aperture value and shutter speed are corrected. Note that in each mode, it is conceivable that the desired brightness cannot be achieved using only the variable exposure control variables. For example, in manual mode, it is conceivable that the desired brightness cannot be achieved by correcting imaging sensitivity alone. In such cases, the fixed exposure control variables are also corrected. Note that in this case, it is preferable to determine the priority of the corrections in advance. The priority may be set by the user.

[0063] If the exposure control amount is corrected by the exposure control amount correction unit 40E, the corrected exposure control amount is used as the exposure control amount when capturing an image. If no correction is made, the exposure control amount set by the exposure control amount setting unit 40C is used as the exposure control amount when capturing an image.

[0064] [Image capture operation] In the imaging device 1 of this embodiment, the exposure conditions (aperture value, shutter speed, and imaging sensitivity) set by the user are maintained as much as possible, while the exposure during imaging is controlled as much as possible using only the variable ND filter 13. To achieve this, in the imaging device 1 of this embodiment, the exposure control amounts at the start of imaging are set as follows:

[0065] FIG. 7 is a flowchart showing the procedure for setting the exposure control amount when starting image capture.

[0066] First, when an instruction to start imaging is given, photometry processing is performed (step S1). The instruction to start imaging is given by pressing the record button. The exposure amount for each area is obtained by photometry.

[0067] Next, an exposure control amount is set based on the photometry result (step S2). This exposure control amount is a temporary exposure control amount. The exposure control amount is set according to the exposure control mode that has been set. Specifically, it is set as follows:

[0068] When the exposure control mode is set to auto mode, the variable ND filter 13 is set to the center value of its movable range, and the remaining exposure control amounts are then set to achieve the desired brightness (for example, proper exposure), i.e., the aperture value, shutter speed, and imaging sensitivity.

[0069] When the exposure control mode is set to aperture priority mode, the aperture value is fixed and the remaining exposure control parameters are set to achieve the desired brightness. That is, the shutter speed, imaging sensitivity, and light reduction rate are set. The aperture value is determined based on information from the operation unit 36.

[0070] When the exposure control mode is set to the shutter speed priority mode, the shutter speed is fixed and the remaining exposure control parameters are set to achieve the desired brightness. That is, the aperture value, imaging sensitivity, and light reduction rate are set. The shutter speed is determined based on information from the operation unit 36.

[0071] When the exposure control mode is set to manual mode, the aperture value and shutter speed are fixed, and the remaining exposure control parameters are set to achieve the desired brightness. That is, the imaging sensitivity and the light reduction rate are set. The aperture value and shutter speed are determined based on information from the operation unit 36.

[0072] Next, an estimated exposure change amount is calculated based on the photometry results (step S3). In this embodiment, the estimated exposure change amount is calculated by determining the exposure range that covers the darkest area to the brightest area in the image based on the photometry results for each area.

[0073] Next, an estimated exposure fluctuation range S is calculated based on the estimated exposure change amount (step S4). The estimated exposure fluctuation range S is calculated by calculating an estimated exposure fluctuation range Sa on the darker side and an estimated exposure fluctuation range Sb on the brighter side, based on the exposure amount M when the exposure control amount was set.

[0074] Next, the settable range R of the variable ND filter 13 is calculated based on the movable range of the variable ND filter 13 (step S5). The settable range R of the variable ND filter 13 is calculated by calculating a settable range Ra in the direction of decreasing the reduction rate and a settable range Rb in the direction of increasing the reduction rate, using the current setting value N of the variable ND filter 13 as a reference.

[0075] Next, based on the calculation results of the estimated exposure fluctuation range S and the settable range R of the variable ND filter 13, it is determined whether or not the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13 (step S6).

[0076] Here, the case where the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13 means that the predicted fluctuation range of the exposure falls within the settable range R of the variable ND filter 13 (see FIG. 4). In this case, exposure can be controlled solely by the variable ND filter 13 during video capture.

[0077] On the other hand, when the estimated exposure fluctuation range S is not included in the settable range R of the variable ND filter 13, this means that the predicted fluctuation range of the exposure amount does not fall within the settable range R of the variable ND filter 13 (see FIG. 5). In this case, exposure cannot be controlled by the variable ND filter 13 alone during video capture. In other words, it becomes necessary to change other exposure control variables during capture.

[0078] Therefore, if it is determined in step S6 that the estimated exposure fluctuation range S is not included in the settable range R of the variable ND filter 13 (the determination in step S6 is "No"), the exposure control amount (provisional exposure control amount) set in step S2 is corrected (step S7). The exposure control amount is corrected, for example, as follows: First, the setting value of the variable ND filter 13 is changed so that the estimated exposure fluctuation range is included in the settable range of the variable ND filter 13. That is, the currently set light amount reduction rate is changed. After the setting value of the variable ND filter 13 is changed, the other exposure control amounts are changed. That is, the aperture value, shutter speed, and imaging sensitivity are changed so that the desired brightness is achieved under the newly set light amount reduction rate. The corrected exposure control amount is used as the exposure control amount when imaging begins. The correction is also performed according to the currently set exposure control mode. Therefore, in aperture priority mode, the shutter speed and imaging sensitivity are corrected. Furthermore, in shutter speed priority mode, the aperture value and imaging sensitivity are corrected. Furthermore, in manual mode, the imaging sensitivity is corrected. If the desired brightness cannot be achieved using only the variable exposure control amount, other exposure control amounts are also corrected. For example, in manual mode, if the desired brightness cannot be achieved using only the imaging sensitivity, the aperture value and shutter speed are also corrected. In this case, each exposure control amount is corrected according to a predetermined priority.

[0079] In step S6, if it is determined that the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13 (if the determination in step S6 is "Yes"), no correction is made, and the set provisional exposure control amount is used as the exposure control amount when imaging begins.

[0080] The above series of steps completes the setting of the exposure control amount when starting image capture. After this, exposure is controlled under the set exposure control amount, and image capture begins.

[0081] As described above, according to the imaging device 1 of this embodiment, the exposure variation range is estimated, and based on the estimation result, it is determined in advance whether exposure can be controlled using only the variable ND filter. If it is determined that exposure cannot be controlled using only the variable ND filter, the exposure control amount is corrected and reset so that exposure can be controlled using only the variable ND filter. This makes it possible to capture moving images by controlling exposure using only the variable ND filter 13 while maintaining the exposure conditions set by the user as much as possible. This also makes it possible to capture natural-looking moving images continuously even when the brightness changes. In other words, since exposure can be controlled using only the variable ND filter 13 as much as possible, it is possible to capture natural-looking moving images continuously even when the brightness changes.

[0082] [Variations] In the imaging device 1 of the above embodiment, when the exposure control mode is the auto mode, the variable ND filter 13 is set to the median value of the movable range, but it may also be configured to be set to a value other than the median value.

[0083] In auto mode, when the variable ND filter 13 is set to the median value of its movable range, there is no need to determine whether or not the exposure control amount needs to be corrected. Therefore, when the exposure control mode is set to auto mode, the subsequent process of determining whether or not the exposure control amount needs to be corrected can be omitted.

[0084] Furthermore, in aperture priority mode, shutter speed priority mode, and manual mode, if the image capture sensitivity is set (that is, in a mode other than auto), the image capture sensitivity is fixed and the remaining exposure control amounts are set.

[0085] Furthermore, if the estimated exposure variation range cannot be brought within the settable range of the variable ND filter 13 even after correction, it is preferable to set the variable ND filter 13 to the median value of its movable range. For example, if the estimated exposure change amount exceeds the movable range of the variable ND filter 13, it is preferable to set the variable ND filter to the median value of its movable range and set other exposure control amounts.

[0086] [Second embodiment] In the imaging device of the first embodiment described above, the exposure fluctuation range is estimated in advance, and the exposure control amount is set when imaging begins so that exposure can be controlled solely by the variable ND filter during imaging. However, the actual exposure does not always fall within the estimated fluctuation range. In the imaging device of this embodiment, if the estimated exposure fluctuation range changes during imaging, the exposure control amount is corrected (changed) so that the changed estimated exposure fluctuation range is included in the settable range of the variable ND filter.

[0087] Since the device configuration is the same as the imaging device of the first embodiment, only the method of exposure control during imaging will be described here.

[0088] FIG. 8 is a flowchart showing the procedure for exposure control during image capture.

[0089] First, photometry processing is performed (step S10), and then, based on the photometry result, it is determined whether or not the brightness (exposure amount) of the subject has changed (step S11).

[0090] When it is determined that the brightness of the subject has changed, an estimated exposure change amount is calculated based on the photometry result (step S12). Next, an estimated exposure fluctuation range S is calculated based on the estimated exposure change amount (step S13). This estimated exposure fluctuation range S calculated during imaging is an example of a third exposure condition range.

[0091] Next, it is determined whether the calculated estimated exposure fluctuation range S has changed (step S14). Specifically, it is determined whether the calculated estimated exposure fluctuation range (third exposure condition range) is different from the previously calculated estimated exposure fluctuation range (first exposure condition range).

[0092] If it is determined that the estimated exposure variation range S has not changed (if the determination in step S14 is "No"), the setting value of the variable ND filter 13 is changed so as to achieve the desired brightness based on the photometry result (step S18). That is, in this case, since exposure can be controlled only by the variable ND filter 13, only the setting value of the variable ND filter 13 is changed. Thereafter, the variable ND filter 13 is controlled so as to achieve the changed reduction rate, thereby controlling the exposure (step S19).

[0093] On the other hand, if it is determined that the estimated exposure fluctuation range S has changed (if the determination in step S14 is "Yes"), it is determined whether the estimated exposure fluctuation range S after the change is included in the settable range R of the variable ND filter 13. In other words, it is determined whether exposure can still be controlled using only the variable ND filter after the change.

[0094] In this case, first, the settable range R is calculated based on the current setting value of the variable ND filter 13 (step S15). Next, based on the calculated settable range R, it is determined whether the estimated exposure fluctuation range S is included in the settable range R (step S16).

[0095] If it is determined that the estimated exposure variation range S is included in the settable range R of the variable ND filter 13 (if the determination in step S16 is "Yes"), the setting value of the variable ND filter 13 is changed based on the photometry result so as to achieve the desired brightness (step S18). That is, in this case too, exposure can be controlled only by the variable ND filter 13, so only the setting value of the variable ND filter 13 is changed. Thereafter, the variable ND filter 13 is controlled so as to achieve the changed reduction rate, thereby controlling the exposure (step S19).

[0096] On the other hand, if it is determined that the estimated exposure fluctuation range S is not included in the settable range R of the variable ND filter 13 (if the determination in step S16 is "No"), the exposure control amount is set so that the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13 (step S17). In this case, first, the reduction rate of the variable ND filter 13 is set so that the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13. Thereafter, the other exposure control amounts are set based on the set reduction rate. That is, the aperture value, shutter speed, and imaging sensitivity are set. At this time, each exposure control amount is set according to the setting of the exposure control mode. Thereafter, the exposure is controlled using the set exposure control amount (step S19).

[0097] After the exposure control, it is determined whether or not an instruction to end imaging has been issued (step S20). If an instruction to end imaging has been issued, the process ends. On the other hand, if an instruction to end imaging has not been issued, the process returns to step S10, and the above series of processes are repeated.

[0098] As described above, according to the imaging device of this embodiment, the fluctuation range of the exposure amount is estimated even during imaging, and the exposure control amount other than that of the variable ND filter is adjusted as necessary. In other words, the exposure control amount other than that of the variable ND filter is adjusted only when it is determined that exposure cannot be controlled using only the variable ND filter. This makes it possible to control exposure during imaging using only the variable ND filter as much as possible.

[0099] [Third embodiment] When the exposure control mode is set to the auto mode, it is preferable to control the exposure during image capture as follows.

[0100] FIG. 9 is a flowchart showing the procedure for exposure control during image capture when the exposure control mode is the auto mode.

[0101] Here, it is assumed that the variable ND filter 13 is set to the median value of the movable range and the setting imaging is started.

[0102] First, photometry processing is performed (step S30), and then, based on the photometry result, it is determined whether or not the brightness (exposure amount) of the subject has changed (step S31).

[0103] If it is determined that the brightness of the subject has changed, it is then determined whether exposure can be controlled solely by the variable ND filter 13 (step S32). In this case, it is determined whether the changed exposure amount is within the settable range of the variable ND filter 13. If the changed exposure amount is within the settable range of the variable ND filter 13, it is determined that exposure can be controlled solely by the variable ND filter 13.

[0104] If it is determined that exposure can be controlled using only the variable ND filter 13 (if the determination in step S32 is "Yes"), the setting value of the variable ND filter 13 is changed (step S33). That is, the setting value (light amount reduction rate) of the variable ND filter 13 is changed so as to achieve the desired brightness. Thereafter, the variable ND filter 13 is controlled to achieve the changed reduction rate, thereby controlling the exposure (step S35).

[0105] On the other hand, if it is determined that exposure cannot be controlled using only the variable ND filter 13 (if the determination in step S32 is "No"), an exposure control amount is set (step S34). That is, in this case, the variable ND filter 13 is outside the settable range, so the exposure control amount is set including other exposure control amounts. The exposure control amount here is set, for example, as follows:

[0106] FIG. 10 is a flowchart showing the procedure for setting the exposure control amount.

[0107] First, an estimated exposure change amount is calculated based on the photometry result (step S34a). Next, an estimated exposure fluctuation range S is calculated based on the calculated estimated exposure change amount (step S34b). Next, a settable range R of the variable ND filter 13 is calculated based on the movable range of the variable ND filter 13 (step S34c). Next, based on the calculated estimated exposure fluctuation range S and the settable range R of the variable ND filter 13, the setting value (light intensity reduction rate) of the variable ND filter 13 is changed so that the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13 (step S34d). At this time, the change is made under the condition of minimum change amount. This reduces the amount of change in other exposure control amounts. Next, exposure control amounts other than the variable ND filter are changed so that the desired brightness is achieved under the newly set reduction rate (step S34e). In this case, the aperture value, shutter speed, and imaging sensitivity are changed according to a predetermined priority order. The priority order is preferably set taking into consideration the continuity of the moving image, etc. In other words, it is preferably set so that the moving image captured after the change does not appear unnatural. As an example, the order of priority can be set as follows: shutter speed within the range from the maximum value to half the maximum value, imaging sensitivity, shutter speed at half the maximum value, and aperture value. In this case, the shutter speed is first changed within the range from the maximum value to half the maximum value. If the desired brightness cannot be achieved by this change alone, the imaging sensitivity is further changed. If the desired brightness cannot be achieved even by changing the imaging sensitivity, the shutter speed is further changed. That is, the shutter speed is changed to half the maximum value. Furthermore, if the desired brightness cannot be achieved even by changing the shutter speed, the aperture value is further changed. In this way, the exposure control amounts of the aperture value, shutter speed, and imaging sensitivity are changed according to a predetermined priority, and exposure control amounts that achieve the desired brightness are set.

[0108] Once the exposure control amount is set, the exposure is controlled using the set exposure control amount (step S35). After exposure control, it is determined whether an instruction to end imaging has been issued (step S36). If an instruction to end imaging has been issued, the process ends. On the other hand, if an instruction to end imaging has not been issued, the process returns to step S30, and the above series of processes are repeated.

[0109] As described above, when the variable ND filter 13 falls outside its settable range, the exposure control amount other than that of the variable ND filter is changed to ensure the settable range of the variable ND filter 13. At that time, the exposure control amount other than that of the variable ND filter is changed in accordance with a predetermined priority order.

[0110] [Variations] If the variable ND filter is outside its settable range, the variable ND filter may be configured to be set to the median value of its movable range when setting the exposure control amount.

[0111] Furthermore, when changing the exposure control amount other than the variable ND filter, the user may be allowed to set the priority order of the exposure control amount to be changed.

[0112] [Fourth embodiment] In the imaging device of this embodiment, when calculating the estimated exposure fluctuation range, the estimated exposure fluctuation range is calculated with a certain margin. Specifically, the estimated exposure fluctuation range is calculated by adding a predetermined margin (fluctuation width) to the estimated exposure change amount obtained from the photometry result.

[0113] Note that, except for the difference in the method of calculating the estimated exposure fluctuation range, the imaging device of this embodiment is the same as that of the imaging device of the first to third embodiments. Therefore, only the method of calculating the estimated exposure fluctuation range will be described here.

[0114] FIG. 11 is a conceptual diagram of calculation of the estimated exposure fluctuation range.

[0115] As described above, the estimated exposure fluctuation range S is calculated by adding predetermined margins α and β to the estimated exposure change amount A (Amin to Amax) obtained from the photometry results. The margins α and β are prepared separately: a margin α added to the darker side (negative side) and a margin β added to the brighter side (positive side). The added margins α and β are determined based on the estimated exposure change amount.

[0116] FIG. 12 is a diagram showing an example of a margin added to the estimated amount of change in exposure.

[0117] According to the example shown in the figure, for example, if the estimated exposure change amount A is 13 to 15 (Amin=13, Amax=15), the dark side margin α is 2 and the bright side margin β is 1. Therefore, in this case, the estimated exposure variation range S is set to a range of 11 to 16. Also, for example, if the estimated exposure change amount A is 0 to 2 (Amin=0, Amax=2), the dark side margin α is 2 and the bright side margin β is 3. Therefore, in this case, the estimated exposure variation range S is set to a range of -2 to 5. Note that if the estimated exposure change amount A straddles the ranges defined in the table of FIG. 12, the larger margin is prioritized. For example, if the estimated exposure change amount A is 6 to 7, the dark side margin α can be 3 to 4 and the bright side margin β can be 3 to 4, but the larger margin is prioritized. Therefore, in this case, the dark side margin α is 4 and the bright side margin β is 4. If the estimated exposure fluctuation range after adding the margin exceeds the upper or lower limit of the exposure amount, it is set to the upper or lower limit. For example, in the example of Figure 12, if it exceeds 16EV or -4EV, it is set to 16EV or -4EV.

[0118] In this way, by adding a predetermined margin to the estimated exposure change amount obtained from the measurement results and calculating the estimated exposure fluctuation range, it is possible to set the estimated exposure fluctuation range more appropriately. In other words, when capturing a moving image, it is possible to set the predicted exposure fluctuation range more appropriately.

[0119] [Variations] In the above embodiment, the margins α and β are set based on the estimated exposure change amount A, but the method for setting the added margins α and β is not limited to this. Other examples of the margin setting method will be described below.

[0120] (1) Margin setting method 1 Margins are set according to the scene to be shot. In this case, the margins α and β to be added for each scene are determined in advance. When shooting, the scene is identified and information on the margins α and β to be added is obtained.

[0121] The scene can be identified by a method selected by the user or by an automatic scene recognition by the imaging device. The automatic scene recognition method can use, for example, a method that utilizes photometry results. For example, a method that identifies a scene from exposure information obtained by photometry can be used. FIG. 13 is a diagram showing an example of the relationship between exposure and scene. As shown in the figure, a certain degree of scene (image capture scene information) can be identified from the exposure. According to the example shown in the figure, for example, if the exposure range of each divided area is 13EV to 15EV, the scene can be identified as a sunny day image capture scene. Therefore, in this case, margins α and β prepared for sunny day image capture scenes are added to the estimated exposure change amount to set the estimated exposure variation range. Other known techniques can also be used to identify an image capture scene.

[0122] When the user specifies a scene, for example, a method can be adopted in which a list of selectable imaging scenes is displayed on the display unit 34 and the user is allowed to select one using the operation unit 36.

[0123] (2) Margin setting method 2 The optimal margins are set using the user's past imaging history. That is, optimal margins α and β are set based on the user's past imaging tendencies. In this case, the fluctuation range of the exposure is measured each time a video is captured, and information on the measured fluctuation range is recorded. The fluctuation range is measured and recorded in both the darkening direction and the brightening direction. When calculating the estimated exposure fluctuation range, the margin α on the darkening side and the margin β on the brightening side are set based on the recorded fluctuation range. For example, the average value of the recorded fluctuation range is set as the margin. Alternatively, the maximum value of the recorded fluctuation range is set as the margin. This process is performed by the system control unit 40. Information on the fluctuation range is recorded, for example, in the auxiliary storage unit 32, which is configured as an internal memory.

[0124] (3) Margin setting method 3 Set the margins manually. If the expected fluctuation range of exposure when shooting video is known in advance, that information can be used to set the margins α and β. For example, if the location (scene) to be shot is decided, the expected fluctuation range of exposure can be known to some extent in advance. For example, when shooting only outdoors, the range of fluctuation is expected to be small because it does not get dark suddenly. On the other hand, when shooting at a live music venue, wedding hall, etc., scenes with sudden changes in brightness are expected, so the range of fluctuation is expected to be large.

[0125] In this example, for example, a margin setting screen is displayed on the display unit 34, and the margins α and β are manually set using the operation unit 36.

[0126] (4) Margin setting method 4 The fluctuation range of the exposure amount is measured and an optimum margin is set. For example, if the area (location) to be imaged is predetermined, the fluctuation range of the exposure amount of the area to be imaged is measured in advance and the margin is set using the measurement results.

[0127] [Other embodiments] (1) Transmittance control element In the above embodiment, an example has been described in which an electronic variable ND filter is used as the transmittance control element, but the optical element that can be used as the transmittance control element is not limited to this. Any optical element that can change the transmittance may be used. For example, other light control elements such as a liquid crystal optical element may also be used as the transmittance control element.

[0128] (2) Imaging device The imaging device is not limited to a standalone device, but also includes a device incorporated into other devices. For example, the imaging device may include a camera incorporated into a smartphone, a personal computer, a wearable device, etc.

[0129] (3) Processor Processors that control the processing of the present invention include CPUs (Central Processing Units), which are general-purpose processors, programmable logic devices (PLDs), such as FPGAs (Field Programmable Gate Arrays), which are processors whose circuit configuration can be changed after manufacture, and dedicated electrical circuits, such as ASICs (Application Specific Integrated Circuits), which are processors with circuit configurations designed specifically to execute specific processing.

[0130] A single control unit and signal processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same or different types (for example, multiple FPGAs, or a combination of a CPU and an FPGA).

[0131] Furthermore, multiple control units and signal processing units may be configured in one processor. Examples of configuring multiple control units and signal processing units in one processor include, first, a configuration in which one processor is configured by combining one or more CPUs and software, and this processor functions as multiple control units and signal processing units. Second, a configuration in which a processor is used that realizes the functions of an entire system, including multiple control units and signal processing units, in a single IC (Integrated Circuit) chip, as typified by a System on Chip (SoC).

[0132] In this way, the various control units and signal processing units are configured as hardware structures using one or more of the various processors described above.

[0133] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit that combines circuit elements such as semiconductor elements. [Explanation of symbols]

[0134] 1. Imaging device 10 Imaging lens 11 Lens 12 apertures 13 Variable ND Filter 14 Lens drive unit 15 Aperture drive unit 16 ND filter drive unit 20 Image sensor 20A Image sensor light receiving surface 22 Image sensor drive unit 24 Analog signal processing section 26 ADC 28 Main memory 30 Digital signal processing section 32 Auxiliary storage 34 Display section 36 Control section 40 System control section 40A Exposure control mode discrimination section 40B Photometry section 40C Exposure control amount setting section 40D Exposure change amount estimation unit 40E Exposure control amount compensation section A Estimated exposure change Amin Minimum estimated exposure change Amax Maximum estimated exposure change amount M Exposure amount when exposure control amount is set N Variable ND filter setting value R Variable ND filter setting range Ra: Settable range in the direction of decreasing the rate of decrease in light intensity Rb Settable range in the direction of increasing the rate of decrease in light intensity S Estimated exposure fluctuation range Sa Estimated exposure fluctuation range on the dark side Sb Estimated exposure fluctuation range on the bright side a11~a88 Divided area α margin β margin S1~S7 Exposure control setting procedure when starting imaging S10~S20 Exposure control procedure during shooting S30~S36 Exposure control procedure during shooting when the exposure control mode is auto mode S34a to S34e: Exposure control amount setting process procedure

Claims

1. A transmittance control element; a processor, The processor: Estimating the amount of exposure change based on the photometry results; determining a value to be added to the amount of change in exposure based on the estimated amount of change in exposure; adding the determined value to the exposure change amount to calculate a first exposure condition range; determining whether the first exposure condition range is included in a second exposure condition range to which the control range of the transmittance control element can be applied; If the first exposure condition range is not included in the second exposure condition range, the exposure conditions are changed so that the calculated first exposure condition range is included in the second exposure condition range. An imaging device, the value is determined based on a table that sets the relationship between the exposure dose and the value; the table is set by dividing the exposure amount into at least a first range and a second range, When the estimated exposure change amount straddles the first range and the second range, the value set for the first range or the value set for the second range, whichever is set larger, is adopted. Imaging device.

2. In the table, the value α is set to be added to the darker side, and the value β is set to be added to the brighter side. The imaging device according to claim 1 .

3. When the exposure amount is in a range equal to or greater than a first threshold, the value α is set to be greater than the value β. The imaging device according to claim 2 .

4. When the exposure amount is in a range equal to or less than a second threshold, the value α is set to be smaller than the value β. The imaging device according to claim 2 or 3.

5. The value α and the value β are set to be equal when the exposure amount is in a range smaller than a first threshold value and larger than a second threshold value. The imaging device according to claim 2 .

6. The value is When the exposure amount is in a range equal to or greater than a first threshold, the value α is set to be greater than the value β, When the exposure amount is in a range equal to or less than a second threshold, the value α is set to be smaller than the value β, In a range where the exposure amount is smaller than the first threshold value and larger than the second threshold value, the value α and the value β are set to be equal. The imaging device according to claim 2 .

Images