JP7646294B2 - Imaging device and control method thereof - Google Patents

Description

The present invention relates to an imaging device and a control method thereof, and in particular to an imaging device having an electronic device that generates heat during operation.

In recent years, small yet highly functional portable electronic devices such as digital cameras and mobile phones have become increasingly popular. For example, even with the same video capture function, digital cameras can now record at higher frame rates by applying more advanced image processing such as filter processing and image correction to higher pixel image data. In addition, the adoption of functions other than video capture is also increasing, such as the ability to wirelessly transfer captured still images and video files.

To achieve these functions, electronic devices such as the image sensor, wireless module, and image processing CPU become heat sources, causing the temperature inside the digital camera body to rise. Therefore, it is necessary to limit operation so that the electronic devices do not exceed their guaranteed upper operating temperature. Furthermore, a rise in temperature of the image sensor leads to deterioration of captured images. In addition, because the electronic devices are mounted inside a small housing, the exterior of the housing also generates heat during operation. Because the user directly touches the exterior of the housing, it was necessary to control its temperature so that it remained below a certain level.

Patent document 1 discloses an imaging device that calculates and displays the time until the temperature inside the camera body reaches the video recording stop time from the amount of change in the measured value of a thermometer placed inside the camera body during video shooting. The imaging device of Patent Document 1 stops video recording when a predetermined temperature is reached.

JP 2012-165372 A

In the conventional technology disclosed in the above-mentioned Patent Document 1, video recording is stopped when it becomes necessary to stop video recording due to a rise in temperature of the digital camera's housing. This makes it possible to control the temperature of the digital camera's housing so that it remains at or below a predetermined temperature. Furthermore, by displaying the time from when video recording starts to when it stops, it is possible to notify the user in advance that video recording will stop.

However, with the imaging device disclosed in Patent Document 1, it is not possible to predict the time it will take for the housing to reach a certain temperature unless video recording is started. As a result, after starting video recording, the user may find that the video recording time is shorter than the user expected before starting recording, and the user may not be able to record the necessary scenes.

The object of the present invention is to provide a means for predicting the available operation time when a specified function is executed while waiting to be executed.

In order to achieve the above-mentioned object, the present invention provides an imaging device that generates and records a moving image from a subject, comprising a first temperature sensor that acquires a first temperature at a first location inside a housing of the imaging device, a second temperature sensor that acquires a second temperature at a second location inside the housing of the imaging device different from the first location, and a prediction means for calculating a remaining moving image recordable time, wherein the prediction means calculates a current time based on a difference between the first temperature acquired by the first temperature sensor and the second temperature acquired by the second temperature sensor and a function h that represents a change over time between the difference between the first temperature and the second temperature during moving image recording, calculates an environmental temperature from the difference between the current time and a predicted temperature calculated based on a function f that represents a change over time of the first temperature during moving image recording and the first temperature acquired by the first temperature sensor, and calculates the remaining moving image recordable time from the difference between the current time and a moving image recording stop time calculated based on the difference between the allowable temperature at the first location and the environmental temperature and the function f, and the current time .

According to the present invention, it is possible to predict the operational time when a specific function is executed while waiting to be executed.

1 is an external view of a digital camera 100 according to a first embodiment. 1 is a block diagram showing an example of the configuration of a digital camera 100 according to a first embodiment. 4 is a diagram showing an example of the arrangement of temperature sensors inside the housing of the digital camera 100 according to the first embodiment. FIG. 5 is a diagram showing changes over time in the output value of a temperature sensor inside the housing of the digital camera 100 according to the first embodiment. FIG. 4 is a flow of control for predicting available moving image recordable time of the digital camera 100 according to the first embodiment. 3 is an example of a display screen of the digital camera 100 according to the first embodiment. FIG. 11 is a diagram showing temperature changes over time inside the housing of a conventional digital camera during video recording.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following description of the embodiment, the same configurations, operations, and processes are given the same reference numerals in the drawings. In addition, in this embodiment, a digital camera, which is an image capture device, will be described as an example of an electronic device according to the present invention, but this is merely an example and is not limiting.

First, the conventional control of operational restrictions in response to temperature rise in a digital camera will be described with reference to FIG. 7. FIG. 7 shows an example of temperature changes over time inside the housing of a digital camera during video recording.

Curve 701 shows the temperature change over time inside the housing of the digital camera while it is recording a video. Curve 702 shows the temperature change over time inside the housing of the digital camera while it is on standby before recording a video. While it is on standby, the image processing unit does not perform video encoding processing or the process of writing video image data to the recording medium, so the temperature rise inside the housing is more gradual than during video recording.

For example, if the operating limit temperature is _KL , then during video recording (curve 701) at a certain environmental temperature _KE , the operating limit temperature is reached at time _t1 after the start of video recording. In other words, when video recording is started, time _t1 is the available video recording time. On the other hand, during video standby (curve 702), the operating limit temperature _KL is not reached.

Next, curve 703 shows the temperature change over time inside the housing when movie recording is started at time _tS during movie standby. At this time, the movie stop temperature _KL is reached at time _t2 after the start of movie recording. In other words, in this case, the movie recordable time expected before the start of recording becomes shorter after the actual start of recording.

Therefore, since the rate of temperature rise inside the housing differs between when the camera is on standby and when it is recording a video, the video recordable time _t2 cannot be predicted when the camera is on standby by observing the amount of temperature change using a thermometer.

(First embodiment)
An imaging device, which is an electronic device to which the present invention can be applied, will be described with reference to Fig. 1. Fig. 1 is an external view showing a digital camera 100 as an example of an imaging device according to a first embodiment. Fig. 1(a) is a front perspective view of the digital camera 100, and Fig. 1(b) is a rear perspective view of the digital camera 100.

The communication terminal 101 is a communication terminal that enables the digital camera 100 to communicate with the lens unit 200 (detachable) described below.

The terminal cover 102 is a cover for protecting a connector (not shown) for connecting external devices such as a connection cable.

The outside viewfinder display unit 103 is a display unit provided on the top surface of the camera, and displays the settings of the digital camera 100, such as the shutter speed and aperture.

The mode change switch 104 is an operation unit for switching between various modes related to shooting and playback.

The shutter button 105 is an operation unit for issuing shooting instructions. For example, pressing the button halfway (SW1) generates a shooting preparation instruction, and pressing the button all the way (SW2) executes shooting.

The grip unit 106 is a holding unit shaped to be easily gripped with the right hand when the user holds the digital camera 100. In this embodiment, the shutter button 105 and the main electronic dial 171, which will be described later, are located in positions that can be operated with the index finger of the right hand when the digital camera is held by gripping the grip unit 106 with the little finger, ring finger, and middle finger of the right hand. In the same position, the sub electronic dial 173, which will be described later, is located in a position that can be operated with the thumb of the right hand.

The display unit 107 displays images and various information. The display unit 107 has a touch panel 170a on its surface, and the touch panel 170a can detect touch operations on the display surface (operation surface) of the display unit 107.

The eyepiece 108 is the eyepiece of an eyepiece finder (a peer-in type finder), and the user can view the image displayed on the internal EVF 213 (Electric View Finder) described below through the eyepiece 108.

The eyepiece detection unit 109 is an eyepiece detection sensor that detects whether the user places his/her eye on the eyepiece unit 108.

The lid 110 is the lid of the slot that stores the recording medium 260 described below.

The main electronic dial 171 is a rotary operating member, and by turning this main electronic dial 171, settings such as the shutter speed and aperture can be changed.

The power switch 172 is an operating member that switches the power of the digital camera 100 ON and OFF.

The sub electronic dial 173 is a rotating operation member that can be used to move the selection frame, advance images, etc.

The cross key 174 is a cross key (four-way key) that can be pressed up, down, left, or right. An operation can be performed according to which part of the cross key 174 is pressed.

The SET button 175 is a push button that is primarily used to confirm selected items.

The video button 176 is used to start and stop video capture (recording).

The AE lock button 177 can be pressed while the camera is in standby to lock the exposure state.

The enlargement button 178 is an operation button for turning the enlargement mode ON and OFF in the live view display in the shooting mode. By turning the enlargement mode ON and then operating the main electronic dial 171, the live view image can be enlarged or reduced. In the playback mode, it functions as a enlargement button for enlarging the playback image and increasing the magnification ratio.

The playback button 179 is an operation button for switching between the shooting mode and the playback mode. By pressing the playback button 179 during the shooting mode, the mode switches to the playback mode, and, for example, the most recent image among the images recorded on the recording medium 260 described later can be displayed on the display unit 107.

When the menu button 180 is pressed, a menu screen in which various settings can be made is displayed on the display unit 107. The user can make various settings using the menu screen displayed on the display unit 107, the cross key 174, and the SET button 175.

Figure 2 is a block diagram showing an example of the configuration of a digital camera 100 according to this embodiment. In this embodiment, the digital camera 100 is equipped with a replaceable lens unit 200 that is equipped with a photographing lens.

The lens unit 200 has an aperture 201, an aperture drive circuit 202, an AF drive circuit 203, a lens system control circuit 204, a lens 205, and a communication terminal 206. The lens system control circuit 204 controls each block of the lens unit 200 to realize lens control. For example, the aperture 201 is controlled via the aperture drive circuit 202, and the lens 205 is displaced via the AF drive circuit 203 to adjust the focus. The lens 205 is usually composed of multiple lenses, such as a zoom lens and a focus lens, but is shown here as a single lens for simplicity. The communication terminal 206 is a communication terminal that allows the lens unit 200 to communicate with the digital camera 100, and communicates with the system control unit 250 via the communication terminal 101 described above. The lens unit 200 may be configured to be attached to the digital camera 100.

The shutter 207 is a focal plane shutter that can control the exposure time of the imaging unit 208 by being driven in response to the control of the system control unit 250 described later.

The imaging unit 208 is an imaging element such as a CCD or CMOS that converts the optical image of the subject incident through the lens unit 200 into an electrical signal.

The A/D converter 209 converts the analog signal output from the imaging unit 208 into a digital signal.

The memory control unit 210 controls data transmission and reception between the A/D converter 209, the image processing unit 211 (described later), and the memory 214. The output data from the A/D converter 209 is written to the memory 214 via the image processing unit 211 and the memory control unit 210, or directly via the memory control unit 210.

The image processing unit 211 performs image processing such as predetermined pixel interpolation, resizing such as reduction, and color conversion processing on the output data (image data) from the A/D converter 209 or image data transmitted and received by the memory control unit 210. The image processing unit 211 also performs predetermined calculation processing using the captured image data output from the imaging unit 208 via the A/D converter 209. Based on the obtained calculation results, the system control unit 250 (described later) controls each block related to imaging such as the lens system control circuit 204, the shutter 207, and the imaging unit 208 to perform exposure control and distance measurement control. This allows imaging control such as TTL (through-the-lens) type AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash pre-flash) processing to be performed. The image processing unit 211 further performs predetermined calculation processing using the captured image data, and performs image processing such as TTL type AWB (auto white balance) processing based on the obtained calculation results.

The D/A converter 212 converts the digital signal output from the memory control unit 210 into an analog signal for display.

The display unit 107 and EVF 213 are configured with an LCD, an organic EL, or the like, and perform display according to the output data output from the memory control unit 210 and converted by the D/A converter 212. Live view display is achieved by sequentially transferring and displaying image data acquired via the lens unit 200 and the imaging unit 208 to the display unit 107 or EVF 213. Hereinafter, an image displayed in live view is referred to as a live view image.

The memory 214 stores image data obtained by the imaging unit 208 and converted into digital data by the A/D converter 209, and image data to be displayed on the display unit 107 and EVF 213. The memory 214 has a storage capacity sufficient to store a predetermined number of still images and a predetermined period of moving images and audio. The memory 214 also serves as a memory for displaying images (video memory). The display image data written to the memory 214 is displayed on the display unit 107 and EVF 213 via the memory control unit 210.

The operation unit 70 is a variety of operation members that serve as an input unit that accepts operations from the user. The operation unit 70 includes operation members related to shooting instructions, such as the shutter button 105, movie button 176, and AE lock button 177. It may also include operation members for changing settings, such as the main electronic dial 171, sub electronic dial 173, cross key 174, SET button 175, and menu button 180. In this embodiment, the operation unit 70 also includes a touch panel 170a, a power switch 172, a magnification button 178, and a playback button 179.

The touch panel 170a and the display unit 107 can be configured as an integrated unit. For example, the touch panel 170a is configured so that the light transmittance does not interfere with the display of the display unit 107, and is attached to the upper layer of the display surface of the display unit 107. Then, input coordinates on the touch panel 170a are associated with display coordinates on the display screen of the display unit 107. This makes it possible to provide a GUI (graphical user interface) that gives the user the feeling that they are directly operating the screen displayed on the display unit 107.

In addition to the operation unit 70, the mode changeover switch 104, the first shutter switch 105a, and the second shutter switch 105b are also operation input means capable of inputting various operation instructions to the system control unit 250 described later. The mode changeover switch 104 switches the operation mode of the system control unit 250 to one of a plurality of modes such as a still image shooting mode and a video shooting mode. Modes included in the still image shooting mode include an auto shooting mode, an auto scene discrimination mode, a manual mode, an aperture priority mode (Av mode), a shutter speed priority mode (Tv mode), and a program AE mode (P mode). There are also various scene modes and custom modes that are shooting settings for each shooting scene. The mode changeover switch 104 allows the user to directly switch to one of these modes. Alternatively, after switching to a list screen of shooting modes with the mode changeover switch 104, one of the displayed modes may be selected and switched using other operating members. Similarly, the video shooting mode may also include a plurality of modes.

The first shutter switch 105a is a switch that is turned on when the shutter button 105 provided on the digital camera 100 is pressed halfway, and generates a first shutter switch signal SW1 (a shooting preparation command). The first shutter switch signal SW1 starts shooting preparation operations such as AF (autofocus) processing, AE (autoexposure) processing, AWB (auto white balance) processing, and EF (pre-flash) processing.

The second shutter switch 105b is a switch that is turned ON when the shutter button 105 is fully pressed, and generates a second shutter switch signal SW2 (shooting instruction). In response to the second shutter switch signal SW2, the system control unit 250 reads a signal from the imaging unit 208 and starts a series of shooting processing operations up to writing the captured image to the recording medium 260 as an image file.

The power supply unit 215 consists of a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a lithium ion battery, an AC adapter, etc.

The power supply control unit 216 is composed of a battery detection circuit, a DC-DC converter, a switch circuit that switches between blocks to which electricity is applied, and other components, and detects whether a battery is installed, the type of battery, and the remaining battery power. Based on the detection results and instructions from the system control unit 250, the power supply control unit 216 controls the DC-DC converter and supplies the necessary voltage for the necessary period to each unit, including the recording medium 260.

Various camera settings, including shutter speed and aperture, are displayed on the viewfinder display unit 103 via the viewfinder display unit drive circuit 218.

The non-volatile memory 219 is an electrically erasable and recordable memory, and may be, for example, a Flash-ROM. The non-volatile memory 219 stores constants and programs for the operation of the system control unit 250. The programs referred to here are programs for executing the various flowcharts described later in this embodiment.

The system control unit 250 is a control unit consisting of at least one processor or circuit, and controls the entire digital camera 100. By executing the programs recorded in the non-volatile memory 219 described above, each process of this embodiment, which will be described later, is realized.

In this embodiment, multiple temperature sensors are provided to acquire temperatures at specific locations. The exterior temperature sensor 220a, the imaging unit temperature sensor 220b, and the system control unit temperature sensor 220c are, for example, digital temperature sensors each incorporating an A/D converter (not shown). The temperature measurement value of each temperature sensor is converted to a Celsius temperature value inside the sensor and then periodically input into the system control unit 250 via serial communication.

The arrangement of the temperature sensors according to this embodiment will be described with reference to FIG. 3. FIG. 3 shows an outline of an example of the arrangement of the exterior temperature sensor 220a, the imaging unit temperature sensor 220b, and the system control unit temperature sensor 220c inside the housing when the digital camera 100 is viewed from the rear side.

The exterior temperature sensor 220a is intended to monitor the temperature of the exterior of the housing of the digital camera 100, and is located near the exterior inside the housing and away from the imaging unit 208 or the system control unit 250.

The imaging unit temperature sensor 220b is intended to monitor the temperature of the imaging unit 208 and is located in the peripheral area near the imaging unit 208, for example, on the same board as the imaging sensor mounting board of the imaging unit 208.

The system control unit temperature sensor 220c is intended to monitor the temperature of the system control unit 250 and is located in the periphery near the system control unit 250, for example, on the same board as the system control unit 250 is mounted on.

The eyepiece detection unit 109 is an eyepiece detection sensor that detects the approach (eyepiece) and removal (eye separation) of the eye (object) to the eyepiece unit 108 of the viewfinder (approach detection). The system control unit 250 switches the display unit 107 and EVF 213 between display (display state)/non-display (non-display state) depending on the state detected by the eyepiece detection unit 109. More specifically, at least in the shooting standby state and when the display destination switching is automatic switching, when the eye is not placed near the object, the display unit 107 is turned on to display the object and the EVF 213 is not displayed. Also, when the eye is placed near the object, the EVF 213 is turned on to display the object and the display unit 107 is not displayed.

The eyepiece detection unit 109 uses, for example, an infrared proximity sensor to detect the approach of an object to the eyepiece 108 of the viewfinder that incorporates the EVF 213. When an object approaches, infrared light projected from a light-projecting unit (not shown) of the eyepiece detection unit 109 is reflected and received by a light-receiving unit (not shown) of the infrared proximity sensor. Depending on the amount of infrared light received, it is possible to determine how close the object is to the eyepiece 108 (eyepiece distance). In this way, the eyepiece detection unit 109 detects the proximity of the object to the eyepiece 108.

When an object is detected approaching within a predetermined distance of the eyepiece unit 108 from a non-eyepiece state (non-approaching state), it is detected that the eye has been placed in contact with the object. When an object that was detected as approaching from the eyepiece state (approaching state) moves away from the eyepiece state by a predetermined distance or more, it is detected that the eye has been removed. The threshold for detecting eye placement and the threshold for detecting removal of the eye may be different, for example, by providing a hysteresis. In addition, after detecting eye placement, the eye placement state remains until removal of the eye is detected. After detecting removal of the eye, the non-eye placement state remains until removal of the eye is detected. Note that the infrared proximity sensor is only one example, and other sensors may be used for the eye placement detection unit 109 as long as they can detect the approach of an eye or object that can be considered as an eye placement.

The attitude detection unit 221 detects the attitude of the digital camera 100 with respect to the direction of gravity. Based on the attitude detected by the attitude detection unit 221, it is possible to determine whether the image captured by the imaging unit 208 was captured with the digital camera 100 held horizontally or vertically. The system control unit 250 can add orientation information corresponding to the attitude detected by the attitude detection unit 221 to the image file of the image captured by the imaging unit 208, or rotate and record the image. An acceleration sensor, a gyro sensor, or the like can be used as the attitude detection unit 221. It is also possible to detect the movement of the digital camera 100 (panning, tilting, lifting, whether it is stationary, etc.) using the attitude detection unit 221 such as an acceleration sensor or a gyro sensor.

The communication unit 222 is connected wirelessly or via a wired cable, and transmits and receives video and audio signals. The communication unit 222 can also connect to a wireless LAN (Local Area Network) or the Internet, and can also communicate with external devices via Bluetooth (registered trademark) or Bluetooth Low Energy. The communication unit 222 can transmit images (including live view images) captured by the imaging unit 208 and images recorded on the recording medium 260, and can also receive images and various other information from external devices.

The system timer 223 is a timing unit that measures the time used for various controls and the time of the built-in clock.

The system memory 224 is, for example, a RAM, and stores constants, variables, and programs read from the non-volatile memory 219 for the operation of the system control unit 250.

The recording medium I/F 225 is an interface with a recording medium 260 such as a memory card or a hard disk.

The recording medium 260 is a recording medium such as a memory card for recording captured images, and is composed of a semiconductor memory, a magnetic disk, etc. In this embodiment, the recording medium 260 is configured to be detachable from the digital camera 100.

In this embodiment, the digital camera 100 is controlled to limit its operation so that temperatures related to the digital camera 100, such as the exterior temperature, the imaging unit temperature, and the system control unit temperature, are kept at a predetermined temperature condition. For example, during operation of the digital camera 100, electronic devices such as the imaging unit 208, communication unit 222, image processing unit 211, and system control unit 250 become heat sources, causing the temperature inside the housing to rise. For example, a rise in temperature of the imaging unit 208 will cause degradation of the captured image. For this reason, each electronic device is set with an upper limit temperature at which operation can be guaranteed, and operation must be limited so as not to exceed that upper limit temperature.

In addition, because various electronic devices are mounted inside a small housing, the exterior of the housing also generates heat during operation. Because the exterior of the housing is the part that the user touches directly, an allowable temperature must be set so that it is not too hot to touch, and operation must be restricted to stay below that allowable temperature.

The operational restriction here is to turn off the power to the digital camera 100. Even if the power is not turned off, any operational restriction may be imposed to stop or reduce the operation of parts related to the allowable temperature, such as stopping video recording, stopping image capture or lowering the frame rate, or turning off the display.

Now, referring to Figure 4, we will explain the change over time in the output value of each temperature sensor when the digital camera 100 is set to video capture mode. Below, in Figure 4(a), the horizontal axis represents time and the vertical axis represents temperature, while in Figures 4(b) to 4(d), the horizontal axis represents time and the vertical axis represents temperature.

4A shows an example of the output value of the imaging unit temperature sensor 220b and the output value of the exterior temperature sensor 220a when video recording and recording standby operations are started at the same time and temperature. Curve 401 shows the time change in the output value of the imaging unit temperature sensor 220b during video recording, and curve 402 shows the time change in the output value of the exterior temperature sensor 220a during video recording. Curve 403 shows the time change in the output value of the imaging unit temperature sensor 220b during video standby, and curve 404 shows the time change in the output value of the exterior temperature sensor 220a during video standby. Curves 401 to 404 show values obtained by subtracting the environmental temperature K _E from the output value of each temperature sensor, and the initial temperature is set to 0°C.

The relational equation at this time is shown in Equation 1.

[Equation 1]
y=f ₄₀₁ (t): Relational expression showing curve 401 y=f ₄₀₂ (t): Relational expression showing curve 402 y=f ₄₀₃ (t): Relational expression showing curve 403 y=f ₄₀₄ (t): Relational expression showing curve 404 FIG. 4B shows the time-dependent change in the output value of each temperature sensor when the camera is in a standby state before movie shooting until time _tS and movie recording starts from time _tS . The output value of the imaging unit temperature sensor 220b changes along curve 403 showing the temperature change in the standby state until time _tS , and changes along curve 401 showing the temperature change during movie recording from time _tS . In the standby state before movie recording, the temperature changes along curve 403, and at time _tS , the temperature changes from the state where the temperature becomes temperature _yDC to the state where the temperature changes along curve 401. Therefore, in FIG. 4B, the curve 401 in FIG. 4A is shifted so that the temperature becomes temperature _yDC at time _tS . Similarly, the output value of the exterior temperature sensor 220a changes along a curve 404 until time _tS , and then changes along a curve 402 from time _tS . In Fig. 4B, curves 401 and 402 are set to a temperature of 0°C at time _tO .

Here, if the time from _t0 to _tS is taken as _tC , the relational expression of the curve shown in FIG. 4B is given by Equation 2.

[Equation 2]
y _DC = f ₄₀₃ (t _S ) = f ₄₀₁ (t _S - t _O ) = f ₄₀₁ (t _C )
y _OC = f ₄₀₄ (t _S ) = f ₄₀₂ (t _S - _{t O} ) = f ₄₀₂ (t _C )
Equation 2 indicates that the output value _yDC of the imaging unit temperature sensor 220b at time _tS during video recording standby matches the output value of the imaging unit temperature sensor 220b after time _tC during video recording. Similarly, it indicates that the output value _yOC of the exterior temperature sensor 220a matches the output value of the exterior temperature sensor 220a after time _tC during video recording.

Therefore, from the inverse function of the above-mentioned formula 1, it is possible to predict the time _tC during video standby as shown in formula 3.

[Equation 3]
t _C = f ₄₀₁ ^-1 (y _DC )
t _C =f ₄₀₂ ^-1 (y _OC )
4C shows curves 401 and 402 in FIG. 4B shifted in the time axis direction so that the origin is time _tO , and time _tS = time _tO + time _tC . From equation 4, the time _tDL at which video recording stops can be predicted based on the temperature of imaging unit temperature sensor 220b. At this time, for example, _KDL is the guaranteed operating temperature of imaging unit 208 for outputting an image without image degradation (acceptable), and the time at which this guaranteed operating temperature is not exceeded is the video recording stop time _tDL .

Similarly, the video recording stop time _tOL can be predicted based on the temperature of exterior temperature sensor 220a. _KOL is based on the allowable temperature of the exterior that is tolerable when touched by the user, for example, and the video recording stop time _tOL is the time when this allowable temperature is not exceeded. That is, in Equation 4, _KDL indicates the video recording stop temperature based on the temperature of imaging unit temperature sensor 220b, and _KOL indicates the temperature at which video recording is stopped based on the temperature of exterior temperature sensor 220a.

[Equation 4]
t _DL = f ₄₀₁ ^-1 (K _DL )
t _OL = f ₄₀₂ ^-1 (K _OL )
Using the time _tC calculated by Equation 3, it is possible to predict the available video record time _tDR based on the imaging unit temperature sensor 220b when it is assumed that video recording is started at time _tS during video standby, from Equation 5. Similarly, it is possible to predict the available video record time _tOR based on the exterior temperature sensor 220a. In Equation 5, _tDR indicates the available video record time based on the temperature of the imaging unit temperature sensor 220b, and _tOR indicates the available video record time based on the temperature of the exterior temperature sensor 220a.

[Equation 5]
t _DR = t _DL - t _C
t _OR = t _OL - t _C
Here, Equation 1 indicates a value obtained by subtracting the environmental temperature K _E around the housing of the digital camera 100 from the output value of each temperature sensor, and in this embodiment, Equations 1 to 5 described above are valid only when the environmental temperature K _E is 0° C. However, the actual output value of each temperature sensor depends on the environmental temperature K _E and varies according to the value of K _E.

So, let's define the relationship in equation 6.

[Equation 6]
y=h ₄₀₅ (t)=f ₄₀₁ (t)-f ₄₀₂ (t)
Equation 6 is a function that represents the difference between curves 401 and 402. Curve 405 in FIG. 4C is a curve that is expressed by the relational expression of Equation 6. Unlike Equation 1, Equation 6 does not depend on the environmental temperature K _E. The temperature difference ΔK between curves 401 and 402 after time t _C has elapsed (time t _s ) is uniquely determined. Therefore, if the temperature output difference between the imaging unit temperature sensor 220b and the exterior unit temperature sensor 220a can be obtained, time t _C can be obtained using Equation 6.

This will be described with reference to Fig. 4(d). Fig. 4(d) shows the curves 401 and 402 in Fig. 4(c) shifted by the environmental temperature K _E in the temperature axis direction. In this case, the relational expression (7) is satisfied.

[Equation 7]
t _C =h ₄₀₅ ^-1 (ΔK)
ΔK=K _DC -K _OC
K _DC = y _DC + _KE : output value of imaging unit temperature sensor 220b K _OC = y _OC + _KE : output value of exterior unit temperature sensor 220a Furthermore, based on any of the relational expressions in Equation 1, for example, the environmental temperature _KE can be calculated by Equation 8. Equation 8 is an example using the relational expression showing the curve 402 in Equation 1.

[Equation 8]
K _E =K _OC -y _OC =K _OC -f ₄₀₂ (t _C )
From the above, Equation 4 can be rewritten as Equation 9.

[Equation 9]
t _DL = f ₄₀₁ ^-1 (K _DL - K _E )
t _OL = f ₄₀₂ ^-1 (K _OL - K _E )
By substituting Equation 9 into Equation 5, the available video recording time based on the temperatures of the respective temperature sensors can be predicted.

The imaging unit temperature sensor 220b and the exterior unit temperature sensor 220a have been described as examples. By replacing the imaging unit temperature sensor 220b with the system control unit temperature sensor 220c, it is possible to predict the video recording time until the system control unit 250 reaches the upper limit temperature at which operation can be guaranteed.

In any case, it is preferable to use the output difference value between a temperature sensor installed near the electronic device that is a heat source and a temperature sensor installed near the exterior of the housing that is less affected by the heat generated by the device. By increasing the output difference value between each temperature sensor, the prediction accuracy of the time _tC in Equation 7 is improved, and as a result, the prediction accuracy of the environmental temperature _KE in Equation 8 and the prediction accuracy of the available video recordable time based on the temperatures of each temperature sensor in Equation 5 are improved.

Below, a method for predicting and displaying the remaining operational time (remaining video recording time) of the digital camera 100 according to an embodiment of the present invention will be described with reference to FIG. 5.

Figure 5 is a flowchart for controlling the prediction process of the operable time of the digital camera 100 according to an embodiment of the present invention. Each process in the flowchart in Figure 5 is realized by the system control unit 250 expanding a program stored in the non-volatile memory 219 into the system memory 224, executing it, and controlling each functional block. The flowchart in Figure 5 begins when the digital camera 100 is started up and set to video recording mode, resulting in a video standby state.

In step S501, the system control unit 250 acquires the output value _KDC of the imaging unit temperature sensor 220b and the output value _KOC of the exterior unit temperature sensor 220a at the current time _tS during video standby.

In step S502, a difference value ΔK between the output value K _DC of the imaging unit temperature sensor 220b and the output value K _OC of the exterior unit temperature sensor 220a is calculated.

In step S503, it is determined whether ΔK is greater than a preset threshold ΔK _TH . If ΔK is greater than ΔK _TH , the process proceeds to step S504. If ΔK is equal to or less than ΔK _TH , the process returns to step S501. If ΔK, which is the difference between the output values of the imaging unit temperature sensor 220b and the exterior unit temperature sensor 220a, is too small, the accuracy of the estimation of the time t _C decreases, so steps S501 and S502 are repeated until ΔK becomes greater than the threshold ΔK _TH . The threshold ΔK _TH is a preset value that is determined based on, for example, experimental values and the like as a value that allows an acceptable accuracy of the estimation of the time t _C. The threshold ΔK _TH is stored in advance in the non-volatile memory 219 and is read out by the system control unit 250.

In step S504, a movie recording time _tC corresponding to the difference value ΔK calculated in step S503 is calculated. A different relational expression (temperature curve information) of equation 7 for each of a plurality of movie recording modes is pre-stored in non-volatile memory 219, and system control unit 250 reads out relational expression (7) corresponding to the movie recording mode currently being used to calculate _tC .

In step S505, the environmental temperature K _E is calculated from the moving image recording time t _C calculated in step S504. A different relational expression (8) for each of the multiple moving image recording modes is stored in the non-volatile memory 219, and the system control unit 50 reads out the relational expression (8) that corresponds to the moving image recording mode currently being used to calculate K _E.

In step S506, it is determined whether K _E is greater than a preset threshold value K _TH . If _{K E} is greater than K _TH , the process proceeds to step S507. If K _E is equal to or less than K TH, the process proceeds to step S514. The threshold value K _TH is pre-stored in the non-volatile memory 219 and is read out by the system control unit 250. Here, the threshold value K _TH means an environmental temperature under which the temperature inside the housing of the digital camera 100 does not reach the upper limit temperature for operation. By making this determination, it is possible to skip unnecessary calculation processing in a situation where the environmental temperature K _E is equal to or less than the threshold value K _TH and does not reach the upper limit temperature for operation, and the CPU load can be reduced.

In steps S507 and S508, the video stop time t _DL based on the temperature of imaging unit temperature sensor 220b and the video stop time t _OL based on the temperature of exterior unit temperature sensor 220a are calculated based on the relational equation of equation 4. The relational equation of equation 4 (temperature curve information), which differs for each of the multiple video recording modes, is pre-stored in non-volatile memory 219, and system control unit 250 reads out the relational equation of equation 4 that corresponds to the video recording mode currently being used.

In steps S509 and S510, the remaining moving image recordable time t _DR based on the imaging unit temperature sensor 220b and the remaining moving image recordable time t _OR based on the exterior unit temperature sensor 220a are calculated based on the relational expression (5).

In step S511, it is determined whether _tDR is smaller than _tOR . If _tDR is smaller than _tOR , the process proceeds to step S512. If _tDR is equal to or larger than _tOR , the process proceeds to step S513.

In step S512, the system control unit 250 displays _tDR on the display unit 107 or EVF 213 as the remaining moving image recordable time.

In step S513, that is, when _tDR is equal to or greater than _tOR , the system control unit 250 displays _tOR on the display unit 107 or EVF 213 as the remaining moving image recordable time.

In step S514, that is, if _{K_E} is equal to or less than _{K_TH} , the system control unit 250 does not display the available moving image recordable time on the display unit 107 or EVF 213.

Next, referring to FIG. 6, a method for displaying the available video recording time on the display unit 107 or EVF 213, which is performed in steps S512 and S513, will be described. FIG. 6 is an example of a display screen of the digital camera 100 according to an embodiment of the present invention, and shows an example of displaying the available video recording time on the display unit 107 or EVF 213 in a video standby state. Image data captured by the imaging unit 208 is transferred sequentially to the display unit 107 or EVF 213 and displayed as a live view. Various shooting parameters are superimposed on the live view image.

Time 601 indicates the video recording time available until the digital camera 100 reaches the temperature limit if video recording is started at the current time. If the video standby state continues, the temperature inside the housing of the digital camera 100 rises, and the video recording time displayed as time 601 gradually decreases. If the video recording time available does not meet the recording time expected by the user, the user can take measures such as stopping the imaging operation of the digital camera 100. By stopping the imaging operation, heat generation in the imaging unit 208 and the system control unit 250 can be suppressed, and the video recording time available can be restored.

The above describes an embodiment of the present invention. Note that the system control unit 250 may be controlled by a single piece of hardware, or the entire device may be controlled by multiple pieces of hardware sharing the processing.

According to this embodiment, the available video recording time when video recording is started during video standby is predicted, and the available video recording time can be displayed on the display unit 107 or EVF 213 of the digital camera 100. Before starting video recording, the user can check whether the desired available video recording time is met before starting video recording, improving convenience.

In addition, by using the output difference value ΔK _of two different temperature sensors, the output value _KDC of the imaging unit temperature sensor 220b and the output value KOC of the exterior unit temperature sensor 221a, the time _tC can be calculated without being affected by fluctuations in the environmental temperature _KE .

When ΔK calculated in step S502 described above is small, it is considered that the prediction accuracy of the time _tC in step S504 decreases, and as a result, the prediction accuracy of the available video record time decreases. In this embodiment, by determining whether ΔK is larger than a predetermined threshold value _ΔKTH , it is possible to display the available video record time only when the reliability of the prediction accuracy is high. This makes it possible to reduce the possibility of providing erroneous information to the user.

In this embodiment, the environmental temperature _KE is calculated in step S505. According to the configuration of this embodiment, it is possible to improve the prediction accuracy of the operable time in an environment where the environmental temperature fluctuates.

In addition, by using a temperature sensor required to monitor the temperature inside the housing of the digital camera 100, it is possible to predict the environmental temperature without the need for additional components to obtain the environmental temperature by a separate means.

Other Embodiments
In the first embodiment, two different temperature sensors are used, but for example, when used in an environment where the environmental temperature K _E is considered to be constant, the available video recording time may be calculated using only one temperature sensor inside the housing of the digital camera 100. This has the advantage of reducing the number of parts compared to the first embodiment, resulting in cost benefits.

In addition, by replacing the imaging unit temperature sensor 220b with the system control unit temperature sensor 220c in the first embodiment, it is possible to predict the operating time until the system control unit 250 reaches the upper limit temperature at which it can operate. The type of electronic device that requires the video to be stopped varies depending on the type of video mode of the digital camera 100. For example, in a high frame rate video mode such as shooting Full HD video at 240 fps, the imaging unit 208 tends to consume more power and generate more heat compared to a low frame rate video mode such as shooting Full HD video at 30 fps. Therefore, it is preferable to predict the video recording time using the imaging unit temperature sensor 220b.

On the other hand, in a low frame rate but high resolution video mode, such as shooting 8K video at 30 fps, the load of the development process is higher and the power consumption of the system control unit 250 is higher than in a low resolution video mode, such as shooting Full HD video at 30 fps. Therefore, it is preferable to predict the available video recording time using the system control unit temperature sensor 220c.

As described above, it is possible to configure the temperature sensor used to calculate the available video recording time to be switched depending on the type of video mode.

In the first embodiment, the shorter of the available movie record time _tDR based on the temperature of the imaging unit temperature sensor 220b and the available movie record time _tOR based on the exterior unit temperature sensor 220a is displayed. If the digital camera 100 is equipped with three or more temperature sensors, it is also possible to compare the lengths of the available movie record time based on all the temperature sensors and display the shorter available movie record time.

In the first embodiment, if there is no limit to the available video recording time in step S514, the available video recording time is not displayed. However, for example, an icon indicating that unlimited video recording is possible may be displayed. It is also possible to compare the available video recording time limited by other factors such as card capacity or battery capacity with the available video recording time limited by an increase in the internal temperature of the digital camera 100 case, and display the shorter available video recording time.

In the first embodiment, in FIG. 6, the available video record time is displayed as time, but for example, the available video record time may be notified by displaying a meter suitable for showing time or another icon. Any display configuration may be used as long as it achieves the purpose of notifying the available video record time. Note that it is also possible to display the available video record time taking into account the available recordable capacity of the recording medium 260 as the time 601. If the available recordable capacity of the recording medium 260 is less than the available video record time based on the temperature limit, the available video record time based on the available recordable capacity may be displayed.

Also, if the configuration serves the purpose of predicting and notifying the available operating time before operational restrictions due to temperature conditions are imposed, the available operating time for other functions other than video recording may be notified.

In the first embodiment, video standby is defined as a live view display state, but any operating state may be defined as video standby as long as the feature of the present invention that allows the video recording time to be predicted before video recording is not lost.

The above is a description of the preferred embodiment of the present invention, but the present invention is not limited to the above embodiment within the scope of the technical concept of the present invention, and should be modified and adapted as appropriate depending on the circuit configuration to be targeted. The present invention has been described in detail based on a digital camera as a preferred embodiment, but the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. The present invention is also applicable to any electronic device that has a heat-generating device. For example, the present invention is applicable to personal computers, PDAs, mobile phone terminals, game consoles, electronic book readers, wearable devices such as head-mounted displays, and the like. In any embodiment, the present invention makes it possible to predict the video recording time that is limited by the rise in temperature inside the housing of the electronic device.

The present invention can also be embodied as, for example, a system, device, method, computer program, or recording medium, and specifically may be realized in one device or applied to a system consisting of multiple devices. Each of the means constituting the imaging device according to this embodiment and each of the steps of the control method for the imaging device can also be realized by the operation of a program stored in the memory of a computer, etc. This computer program and a computer-readable recording medium on which this program is recorded are included in the present invention.

The present invention can also be realized by supplying a program that realizes one or more of the functions of the above-mentioned embodiments to a system or device via a network or storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that realizes one or more of the functions.

100 Digital camera 107 Display unit 213 EVF
250 System control unit 219 Non-volatile memory 220a Exterior temperature sensor 220b Imaging unit temperature sensor 220c System control unit temperature sensor 260 Recording medium

Claims (9)

An imaging device that generates and records a moving image from a subject,
a first temperature sensor configured to acquire a first temperature at a first location inside a housing of the imaging device;
a second temperature sensor that acquires a second temperature at a second location inside a housing of the imaging device that is different from the first location;
A prediction means for calculating a possible video recording time ,
The prediction means includes:
determining a current time based on a difference between the first temperature acquired by the first temperature sensor and the second temperature acquired by the second temperature sensor, and a function h that represents a change over time in the difference between the first temperature and the second temperature during video recording;
calculating an environmental temperature from a difference between a predicted temperature calculated based on a function f representing a time change of the first temperature during the current time and the video recording and the first temperature acquired by the first temperature sensor;
The available video recording time is calculated from a difference between the current time and a video recording stop time calculated based on the difference between the allowable temperature of the first location and the environmental temperature and the function f.
1. An imaging device comprising: 2. The imaging device according to claim 1, further comprising a display unit that displays the available moving image recording time. The imaging device according to claim 1 , wherein the prediction means calculates the available moving image recordable time during standby. The imaging device according to claim 1 , further comprising a storage means for storing the function h . The imaging device according to claim 1 , further comprising a storage means for storing the function f . It has multiple video modes,
The imaging apparatus according to claim 4 , further comprising a storage unit that stores the function h for each of the plurality of moving image modes. It has multiple video modes,
The imaging apparatus according to claim 5 , further comprising a storage unit that stores the function f for each of the plurality of moving image modes. A method for controlling an image capturing device that generates and records a moving image from a subject, the image capturing device having a first temperature sensor that acquires a first temperature at a first location inside a housing of the image capturing device, and a second temperature sensor that acquires a second temperature at a second location inside the housing of the image capturing device different from the first location, the method comprising:
determining a current time based on a difference between the first temperature acquired by the first temperature sensor and the second temperature acquired by the second temperature sensor, and a function h that represents a change over time in the difference between the first temperature and the second temperature during video recording;
calculating an environmental temperature from a difference between a predicted temperature calculated based on a function f representing a time change of the first temperature during the current time and the video recording and the first temperature acquired by the first temperature sensor;
determining a video recording available time from a difference between a video recording stop time determined based on a difference between the allowable temperature of the first location and the environmental temperature and the function f, and the current time . A program for causing a computer to execute the control method according to claim 8 .

Images