Imaging apparatus

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] There is known a technique for controlling exposure using a transmittance control element such as a variable neutral density filter (ND filter) (Patent Documents 1-3, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-191310 A [Patent Document 2] JP 2017-62466 A [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 characteristics of a transmittance control element, the imaging device comprising a processor, the processor calculating a first exposure condition range based on 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, changing 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 according to (1) or (2), wherein the processor controls exposure using the transmittance control element in a second exposure condition range during imaging.

[0008] (4) The imaging device of (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 according to (5), wherein the processor determines the exposure control mode, and if the exposure control mode is a manual mode, sets the exposure conditions by fixing the aperture control amount and the shutter speed control amount.

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

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

[0015] (11) The imaging device according to (10), wherein the order of priority is a shutter speed control amount in the range from the maximum value to 1 / 2 the maximum value, a sensitivity control amount, a shutter speed control amount at 1 / 2 the maximum value, and an aperture control amount.

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

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

[0018] (14) Any one of the imaging devices (1) to (11), in which the processor acquires in advance information on the fluctuation range of the exposure of the area where the video is captured, and sets a first exposure condition range based on the acquired information on the fluctuation range of the exposure. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an imaging device; [Diagram 2] Block diagram of exposure control functions [Diagram 3] FIG. 1 shows an example of region division. [Figure 4] Conceptual diagram of judgment on the necessity of correction [Diagram 5] Conceptual diagram of judgment on the necessity of correction [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 a procedure for exposure control during imaging when the exposure control mode is the auto mode. [Figure 10] 1 is a flowchart showing the procedure for setting an exposure control amount. [Figure 11] Conceptual diagram of calculation of estimated exposure fluctuation range [Figure 12] FIG. 13 is a diagram showing an example of a margin added to an estimated amount of change in exposure; [Figure 13] FIG. 1 is a diagram showing an example of the relationship between exposure and scene. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] [First embodiment] In video capture, it is undesirable for the depth of field, sense of motion, and graininess to change during capture, except when a special expression is being aimed for. In general, 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 capture. This allows for continuous, natural-looking video capture 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 the 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 center value of the 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 the present embodiment, an imaging device is provided that can capture natural moving images continuously 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 the present 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. Although only one lens 11 is shown in Fig. 1 for the sake of convenience, the imaging lens 10 includes a plurality of 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 adjusts the focus by moving the focus lens group back and forth along the optical axis. The 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, 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 that varies the rate of reduction of the amount of light. The imaging device 1 of this embodiment uses an electronic variable ND filter 13. The rate of reduction of the amount of light in the electronic variable ND filter changes depending on the voltage applied. The imaging device 1 of this embodiment uses, as an example, a variable ND filter 13 whose rate of reduction of 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 driving unit 16 to change the rate of reduction of the amount of light.

[0030] The imaging element 20 is composed of a color area image sensor. The image sensor is composed of, for example, a CMOS (Complementary Metal-Oxide Semiconductor) type having a predetermined color filter array (e.g., Bayer array, etc.), a CCD (Charged Coupled Device) type image sensor, etc. The imaging element 20 is driven and operated by an imaging element driving unit 22. The imaging device 1 electronically controls the on and off of the imaging element 20 to adjust the exposure time (shutter speed) (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 circuit (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, which has been subjected to predetermined signal processing by the analog signal processor 24, into a digital image signal.

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

[0034] When the imaging element 20 is configured as a CMOS-type image sensor including an ADC and a digital image sensor signal processing section, a signal of each pixel is output from the imaging element 20 as follows. The signal of each pixel is amplified by an analog amplifier section 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 of each pixel into a digital signal and supplies it to the image sensor signal processing section. The image sensor signal processing section performs various signal processing such as digital correlated double sampling processing, digital gain processing, and correction processing on the supplied digital signal of each pixel. The signal that has been subjected to various signal processing by the signal processing section 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 processor 30 performs signal processing such as offset processing, gamma correction processing, demosaic processing, RGB / YCrCb conversion processing, etc. on the image signal converted into a digital signal to generate image data. The digital signal processor 30 is formed of, for example, a microprocessor.

[0037] The auxiliary storage unit 32 mainly stores image data obtained by imaging. The auxiliary storage unit 32 is composed of a built-in memory and / or an external memory. The built-in memory is a memory built into the main body of the imaging device 1. The built-in memory is composed of, for example, a non-volatile semiconductor memory. The external memory is composed of, for example, a memory card, and is loaded 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 also displays live view images during image capture. It is also used as a setting screen when performing 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 on and off the power of the imaging device 1, an operation member (recording button) for instructing the start and end of imaging, an operation member for making various settings, and the like. The operation members for making various settings include, for example, an operation member for setting an exposure control mode, an operation member for setting an aperture value, an operation member for setting a shutter speed, an operation member for setting an imaging sensitivity, and the like. The operation member for setting the exposure control mode is, for example, configured with a mode dial. The exposure control modes include, for example, an auto mode, an aperture priority mode, a shutter speed priority mode, and a manual mode. The auto mode is a mode in which the aperture value, the shutter speed, and the imaging sensitivity are automatically set. The aperture priority mode is a mode in which the shutter speed and the imaging sensitivity are automatically set according to the set aperture value. The shutter speed priority mode is a mode in which the aperture value and the imaging sensitivity are automatically set according to the set shutter speed. The manual mode is a mode in which the aperture value and the shutter speed are manually set. The operation member for setting the aperture value is, for example, configured with 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 capture sensitivity is, for example, an image capture sensitivity dial. These settings can also be configured to be set on a screen using the display unit 34 and operation members such as a cross key. The operation unit 36 ​​outputs a signal according to the operation of each operation member to the system control unit 40.

[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 calculation processing of physical quantities necessary 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, the shutter speed, the imaging sensitivity, and the variable ND filter 13. Hereinafter, the exposure control performed when capturing a moving image with the imaging device 1 of this embodiment will be described.

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

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

[0044] The exposure control mode discrimination unit 40A discriminates the exposure control mode that is set. 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 that is currently set (auto mode, aperture priority mode, shutter speed priority mode, manual mode, etc.) is discriminated 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 imaging element 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 Exposure Value (EV). In the imaging device 1 of this embodiment, the light receiving surface of the imaging element 20 is divided into a plurality of regions, and light is measured 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 imaging device of this embodiment, the light receiving surface 20A of the imaging element 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, the shutter speed, the imaging sensitivity, and the reduction rate of the light amount. In particular, the aperture value, the shutter speed, and the imaging sensitivity are set as exposure conditions. The aperture value is an example of the aperture control amount. The shutter speed is an example of the shutter speed control amount. The imaging sensitivity is an example of the sensitivity control amount. The exposure control amount setting unit 40C sets the exposure control amount that will result in the desired brightness based on the photometry result of the photometry unit 40B. For example, the photometry result of each area is weighted to obtain the total exposure amount, and the exposure control amount that will result in the desired brightness is set based on the obtained total exposure amount. The desired brightness is, for example, a brightness that will result in a proper exposure. Usually, each exposure control amount is set to obtain the proper exposure. Also, for example, when exposure correction or the like is performed, each exposure control amount is set to obtain 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 the auto mode, the variable ND filter 13 is set to the median value of the movable range and each exposure control amount is set. In the aperture priority mode, the aperture value is fixed and each exposure control amount is set. In the shutter speed priority mode, the shutter speed is fixed and each exposure control amount is set. In the 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 so as to achieve the desired brightness. For example, it is set according to a program diagram or the like.

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

[0049] The exposure control amount correction unit 40E corrects each exposure control amount set by the exposure control amount setting unit 40C as necessary. The exposure control amount correction unit 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 estimation unit 40D (estimated amount of exposure change), and the amount of exposure when the exposure control amount is 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 a so-called movable width, which is the range of the reduction rate of the amount of light that can be changed. In the case of the variable ND filter 13 of this embodiment, the movable range is 1 / 4 to 1 / 128.

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

[0051] When 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 a predicted fluctuation range of the exposure amount when a moving image is captured. The estimated exposure fluctuation range S is calculated by determining an estimated exposure fluctuation range Sa on the dark side and an estimated exposure fluctuation range Sb on the bright side based on the exposure amount M when the exposure control amount is set. The exposure amount M when the exposure control amount is set represents the current brightness (exposure amount) of the subject.

[0053] The estimated exposure fluctuation 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 fluctuation range Sa on the darker side. Also, the range from M to Amax becomes the estimated exposure fluctuation range Sb on the brighter side. The estimated exposure fluctuation range S is an example of a first exposure condition range.

[0054] The settable range R of the variable ND filter 13 is a 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 (the currently set light amount reduction rate) as a reference, and determining the settable range Ra in the direction of decreasing the reduction rate (brightening direction) and the settable range Rb in the direction of increasing the reduction rate (darkening direction). When 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. For this reason, 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 Fig. 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 in which the decrease rate is increased 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] When it is determined that the exposure control amount needs to be corrected, the exposure control amount corrector 40E corrects the exposure control amount so that the estimated exposure fluctuation range S is included in the settable range R of the variable ND filter 13. That is, the exposure control amount is corrected so that the estimated exposure fluctuation range Sa on the darker side falls within the settable range Ra in the direction that decreases the decrease rate, and the estimated exposure fluctuation range Sb on the brighter side falls within the settable range Rb in the direction that increases the decrease rate. The correction is performed, for example, in 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] Fig. 6 is a conceptual diagram of correction of the variable ND filter setting. This figure shows an example of correction from the state shown in Fig. 5.

[0060] In the example shown in FIG. 5, the settable range Rb in the direction of increasing the decrease rate is insufficient for 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 decrease rate. In this case, it is preferable to use the minimum correction amount. This makes it possible to reduce the correction amount when correcting other exposure control amounts. 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 is increased.

[0062] After correcting the set value of the variable ND filter 13, other exposure control amounts are corrected. That is, since the set 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 obtained under the new set value (reduction rate of the amount of light). At this time, each exposure control amount is corrected according to the currently set exposure control mode. That is, when the exposure control mode is set to the aperture priority mode, the exposure control amounts other than the aperture value are corrected. Also, when the exposure control mode is set to the shutter speed priority mode, the exposure control amounts other than the shutter speed are corrected. Also, when the exposure control mode is set to the manual mode, the exposure control amounts other than the aperture value and the shutter speed are corrected. Note that in each mode, it is assumed that the desired brightness cannot be set only by the changeable exposure control amount. For example, in the case of the manual mode, it is assumed that the desired brightness cannot be set only by the correction of the imaging sensitivity. In such a case, the fixed exposure control amount is also corrected. Note that in this case, it is preferable to determine the priority order of the corrections in advance. The priority order may be set by the user.

[0063] When the exposure control amount correction unit 40E corrects the exposure control amount, the corrected exposure control amount is used as the exposure control amount when capturing an image. When 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 a procedure for setting the exposure control amount when starting imaging.

[0066] First, when an instruction to start imaging is given, a photometry process 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 provisional 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 the auto mode, the variable ND filter 13 is set to the center value of the movable range, and the remaining exposure control amount is set so as to obtain a desired brightness (for example, proper exposure). That is, the aperture value, shutter speed, and imaging sensitivity are set.

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

[0071] When the exposure control mode is set to the manual mode, the aperture value and the shutter speed are fixed, and the remaining exposure control amount is set so as to obtain the desired brightness. That is, the imaging sensitivity and the reduction rate of the light amount are set. The aperture value and the 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 range of exposure amounts covering the darkest area to the brightest area in the image is obtained based on the photometry results of each area, and the estimated exposure change amount is calculated.

[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 dark side and an estimated exposure fluctuation range Sb on the bright side based on the exposure amount M when the exposure control amount is set.

[0074] 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 S5). For the settable range R of the variable ND filter 13, a settable range Ra in the direction decreasing the reduction rate and a settable range Rb in the direction increasing the reduction rate are calculated based on the current setting value N of the variable ND filter 13.

[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 only 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 is not 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 amounts during capture.

[0078] Therefore, when 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 (when 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 set 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 reduction rate of the amount of light is changed. After changing the set value of the variable ND filter 13, 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 obtained under the newly set reduction rate of the amount of light. The corrected exposure control amount is set as the exposure control amount when imaging is started. The correction is also performed according to the currently set exposure control mode. Therefore, in the case of the aperture priority mode, the shutter speed and imaging sensitivity are corrected. Also, in the case of the shutter speed priority mode, the aperture value and imaging sensitivity are corrected. Also, in the case of the manual mode, the imaging sensitivity is corrected. If the desired brightness cannot be achieved by the variable exposure control amount alone, the other exposure control amounts are also corrected. For example, in manual mode, if the desired brightness cannot be achieved by the image capture sensitivity alone, the aperture value and shutter speed are also corrected. In this case, each exposure control amount is corrected according to a predetermined priority order.

[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 performed 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 imaging. After this, exposure is controlled under the set exposure control amount, and imaging begins.

[0081] As described above, according to the imaging device 1 of the present embodiment, the exposure variation range is estimated, and based on the estimation result, it is determined in advance whether or not the exposure can be controlled only by the variable ND filter. If it is determined that the exposure cannot be controlled only by the variable ND filter, the exposure control amount is corrected and reset so that the exposure can be controlled only by the variable ND filter. This allows the exposure to be controlled only by the variable ND filter 13 while maintaining the exposure conditions set by the user as much as possible, and allows a moving image to be captured. This also allows a moving image to be captured that is natural even if the brightness changes. In other words, since the exposure can be controlled only by the variable ND filter 13 as much as possible, a moving image to be captured that is natural even if 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 the auto mode, when the variable ND filter 13 is set to the center value of the movable range, the process of determining whether or not the exposure control amount needs to be corrected is not necessary. Therefore, when the exposure control mode is set to the auto mode, the process of determining whether or not the exposure control amount needs to be corrected thereafter can be omitted.

[0084] Furthermore, in aperture priority mode, shutter speed priority mode, and manual mode, when 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 by correction, it is preferable to set the variable ND filter 13 to the median value of the 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 the movable range and set other exposure control amounts.

[0086] [Second embodiment] In the imaging device of the first embodiment, the exposure fluctuation range is estimated in advance, and the exposure control amount is set when imaging is started so that exposure can be controlled only 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 that of 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 of exposure control during imaging.

[0089] First, a photometry process is performed (step S10). Next, 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 fluctuation 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 the 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, and the exposure is controlled (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 or not 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 or not the exposure can be controlled by the variable ND filter alone even 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 or not the estimated exposure fluctuation range S is included in the settable range R (step S16).

[0095] 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 S16 is "Yes"), 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 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, and the exposure is controlled (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. After that, 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. After that, the exposure is controlled with the set exposure control amount (step S19).

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

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

[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 of exposure control during imaging 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 its movable range, and setting imaging is started.

[0102] First, a photometry process is performed (step S30). Next, 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 determined whether or not the exposure can be controlled only by the variable ND filter 13 (step S32). In this case, it is determined whether or not 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 the exposure can be controlled only by the variable ND filter 13.

[0104] If it is determined that exposure can be controlled only by 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 so as 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 by the variable ND filter 13 alone (if the determination in step S32 is "No"), an exposure control amount is set (step S34). That is, in this case, since the variable ND filter 13 is outside the settable range, an 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 of the exposure control amount setting process.

[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 calculation results of the estimated exposure fluctuation range S and the settable range R of the variable ND filter 13, the setting value (light amount 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 SS34d). At this time, the change is made under the condition of the minimum change amount. This makes it possible to reduce the change amount of other exposure control amounts. Next, under the newly set reduction rate, the exposure control amounts other than the variable ND filter are changed so that the desired brightness is obtained (step S34e). In this case, the aperture value, shutter speed, and imaging sensitivity are changed in a predetermined priority order. It is preferable that the priority order is set in consideration of the continuity as a moving image, etc. In other words, it is preferable that the priority order is set so that the moving image captured after the change does not look unnatural. As an example, the priority order can be set in the order of shutter speed in the range from the maximum value to 1 / 2 the maximum value, imaging sensitivity, shutter speed 1 / 2 the maximum value, and aperture value. In this case, the shutter speed in the range from the maximum value to 1 / 2 the maximum value is changed first. 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 1 / 2 the maximum value. Also, 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 the predetermined priority order, and the exposure control amount that obtains the desired brightness is set.

[0108] When the exposure control amount is set, the exposure is controlled with the set exposure control amount (step S35). After the exposure control, it is determined whether or not an instruction to end the imaging is given (step S36). If an instruction to end the imaging is given, the process ends. On the other hand, if an instruction to end the imaging is not given, 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 out of 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 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 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 the predetermined margins α and β to the estimated exposure change amount A (Amin to Amax) obtained from the photometry result. The margins α and β are prepared separately: a margin α added to the darker side (- side) and a margin β added to the brighter side (+ 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, when 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 fluctuation range S is set to a range of 11 to 16. Also, for example, when 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 fluctuation range S is set to a range of -2 to 5. Note that, when the estimated exposure change amount A crosses the ranges defined in the table of FIG. 12, the larger margin is prioritized. For example, when 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 Fig. 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 result and calculating the estimated exposure fluctuation range, it is possible to set the estimated exposure fluctuation range more appropriately. In other words, when a moving image is captured, the predicted fluctuation range of the exposure amount can be set 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 of 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 The 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 specified and information on the margins α and β to be added is obtained.

[0121] The scene can be specified by a user selection method, a method in which the imaging device automatically recognizes the scene, or the like. The scene can be automatically recognized by, for example, a method using photometry results, or the like. For example, a method in which the scene is identified from exposure information obtained by photometry, or the like. 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 (imaging scene information) can be identified from the exposure. According to the example shown in the figure, for example, when the range of exposure of each area obtained by dividing is 13EV to 15EV, it can be identified as an imaging scene of fine weather. Therefore, in this case, margins α and β prepared for imaging scenes of fine weather are added to the estimated exposure change amount, and the estimated exposure variation range is set. Other known techniques can be used to specify the imaging scene.

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

[0123] (2) Margin setting method 2 The optimum margin is set by utilizing the user's past imaging history. That is, the optimum margins α and β are set based on the user's past imaging tendency. In this case, the fluctuation range of the exposure is measured each time a video is captured, and the 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. The information on the fluctuation range is recorded, for example, in the auxiliary storage unit 32 composed of an internal memory.

[0124] (3) Margin setting method 3 Set the margins manually. If the expected fluctuation range of the exposure when capturing a video is known in advance, the margins α and β can be set using that information. For example, if the location (scene) to be captured is fixed, the expected fluctuation range of the exposure can be known to some extent in advance. For example, when capturing images only outdoors, the image does not suddenly become dark, so the fluctuation range is expected to be small. On the other hand, when capturing images at live music venues, wedding halls, etc., scenes where the brightness changes suddenly are expected, so the fluctuation range is expected to be large.

[0125] In the case of 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 actually measured and an optimal margin is set. For example, if the area (location) to be imaged is determined in advance, the fluctuation range of the exposure amount of the area to be imaged is actually measured in advance and the margin is set using the measurement results.

[0127] [Other embodiments] (1) Transmittance control element In the above embodiment, an electronic variable ND filter is used as the transmittance control element, but the optical element usable as the transmittance control element is not limited to this. Any optical element capable of changing the transmittance may be used. For example, other light control elements such as a liquid crystal optical element may 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 that is incorporated into other devices. For example, cameras incorporated into smartphones, personal computers, wearable devices, etc. are also included in the imaging device.

[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 having a circuit configuration designed specifically to execute specific processing.

[0130] A control unit and a 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 (e.g., multiple FPGAs, or a combination of a CPU and an FPGA).

[0131] Furthermore, the multiple control units and signal processing units may be configured in one processor. As an example of configuring the multiple control units and signal processing units in one processor, first, there is a form in which one processor is configured by combining one or more CPUs and software, and this processor functions as the multiple control units and signal processing units. Second, there is a form in which a processor is used that realizes the functions of the entire system including the 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 Aperture 13 Variable ND Filter 14 Lens drive unit 15 Aperture drive unit 16 ND filter drive unit 20. Image sensor 20A Light receiving surface of the image sensor 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 Range in which the rate of decrease in Ra light intensity can be set Rb Setting range for 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 amount setting procedure when starting imaging S10~S20 Exposure control procedure during shooting S30~S36 Procedure for exposure control during shooting when the exposure control mode is in auto mode S34a to S34e: Steps for setting the exposure control amount

Claims

1. A processor is provided. 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; the value is determined based on a table in which a relationship between the exposure dose and the value is set; 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. A transmittance control element is provided, The processor, 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; when the first exposure condition range is not included in the second exposure condition range, changing the exposure condition of the imaging device so that the calculated first exposure condition range is included in the second exposure condition range. The imaging device according to claim 1 .

3. In the table, the value α is set to be added to the dark side, and the value β is set to be added to the bright side. The imaging device according to claim 1 .

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

5. When the amount of exposure is in a range equal to or less than a second threshold, the value α is set to be smaller than the value β.

5. The imaging device according to claim 3.

6. 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 3 .

7. The value is When the amount of exposure 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 amount of exposure 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 to each other. The imaging device according to claim 3 .

Images