Image capture device and image capture device control method

Abstract

Provided are: an imaging device that reduces noise included in an output image of an imaging element having a photosensitive layer on a silicon substrate; and a method for controlling said imaging device. This imaging device (1-1) comprises: an imaging element (12) having a photosensitive layer on a silicon substrate; a cooling unit (14) that cools the imaging element (12); a temperature detection unit (16) that detects the temperature of the imaging element (12); and a CPU (26) that functions as a processor, wherein the processor (26) controls the cooling unit (14) on the basis of a first frame rate at which the imaging element (12) is driven, and the temperature of the imaging element (12) detected by the temperature detection unit (16).

Description

[Technical Field]

[0001] The present invention relates to an imaging device and a control method for the imaging device, and more particularly to a technique for reducing noise contained in an output image of an imaging element. [Background technology]

[0002] Patent Document 1 describes the problem that during time-lapse photography, the temperature of the image sensor fluctuates depending on the ambient temperature, causing fixed pattern noise due to dark current to increase or decrease, changing the amount of noise in the recorded video, resulting in unnatural looking video.

[0003] To solve this problem, the imaging device described in Patent Document 1, when performing time-lapse photography, sets the temperature of the imaging element at the time the initial image is acquired as the target temperature, and uses a cooling system to cool or heat the imaging element to maintain the temperature at the target temperature, thereby keeping noise caused by the dark current of the imaging element constant during time-lapse photography.

[0004] Patent Document 2 describes a document camera that includes an imaging unit that captures an image of a subject such as a piece of paper to generate image information, a detection unit that detects the temperature of the imaging unit, and a control unit that changes the frame rate of the imaging unit based on the temperature of the imaging unit detected by the detection unit. This document camera makes it possible to suppress noise in the image information without using a cooling fan. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-162192 [Patent Document 2] Japanese Patent Application Publication No. 2019-220741 Summary of the Invention [Problem to be solved by the invention]

[0006] One embodiment of the technique of the present disclosure provides an imaging device and a control method for the imaging device that reduce noise included in an output image of an imaging element having a photosensitive layer on a silicon substrate. [Means for solving the problem]

[0007] The invention according to a first aspect is an imaging device comprising an imaging element having a photosensitive layer on a silicon substrate, a cooling unit that cools the imaging element, a temperature detection unit that detects the temperature of the imaging element, and a processor, wherein the processor controls the cooling unit based on a first frame rate that drives the imaging element and the temperature of the imaging element detected by the temperature detection unit.

[0008] In the imaging device according to the second aspect of the present invention, the imaging element preferably has sensitivity in the short-wave infrared band.

[0009] In the imaging device according to the third aspect of the present invention, it is preferable that the processor controls the cooling unit to perform cooling when the first frame rate is slower than the reference frame rate.

[0010] In the imaging device according to the fourth aspect of the present invention, it is preferable that when the first frame rate is faster than the reference frame rate, the processor controls the cooling unit by setting the second temperature higher than the first temperature corresponding to the reference frame rate, and when the first frame rate is slower than the reference frame rate, the processor controls the cooling unit by setting the third temperature lower than the first temperature.

[0011] In the imaging device according to the fifth aspect of the present invention, it is preferable that the imaging device further comprises a first memory that stores a target temperature according to a frame rate, and the processor acquires the corresponding target temperature from the first memory according to the first frame rate, and controls the cooling unit based on the acquired target temperature and the temperature of the imaging element detected by the temperature detection unit.

[0012] In the imaging device according to the sixth aspect of the present invention, it is preferable that the processor weakens or suspends cooling of the imaging element by the cooling section when the temperature of the imaging element detected by the temperature detection section is lower than the target temperature.

[0013] A seventh aspect of the invention is an imaging device comprising an imaging element having a photosensitive layer on a silicon substrate, a temperature detection unit that detects the temperature of the imaging element, and a processor, wherein the processor determines a first frame rate based on the temperature of the imaging element detected by the temperature detection unit and drives the imaging element at the determined first frame rate.

[0014] In the imaging device according to the eighth aspect of the present invention, it is preferable that the imaging device further comprises a second memory that stores a first frame rate corresponding to the temperature of the imaging element, and the processor acquires the corresponding first frame rate from the second memory based on the temperature of the imaging element detected by the temperature detection unit, and drives the imaging element at the acquired first frame rate.

[0015] In the imaging device according to the ninth aspect of the present invention, when the processor is set to output images at a second frame rate lower than the first frame rate, if the temperature of the imaging element detected by the temperature detection unit is equal to or higher than a reference temperature, it is preferable that the processor add frame images at the first frame rate and output images at the second frame rate.

[0016] In the imaging device according to the tenth aspect of the present invention, when the processor is set to output images at a second frame rate lower than the first frame rate, if the temperature of the imaging element detected by the temperature detection unit is lower than a reference temperature, it is preferable that the processor reduces the first frame rate to the second frame rate.

[0017] In the imaging device according to the eleventh aspect of the present invention, it is preferable that the processor drives the imaging element at the first frame rate to start imaging when the temperature of the imaging element detected by the temperature detection section reaches the target temperature.

[0018] A twelfth aspect of the invention is a control method for an imaging device that includes an imaging element having a photosensitive layer on a silicon substrate, a cooling unit that cools the imaging element, a temperature detection unit that detects the temperature of the imaging element, and a processor, the control method for an imaging device including the steps of: the processor driving the imaging element at a first frame rate to capture time-series images; the temperature detection unit detecting the temperature of the imaging element; and the processor controlling the cooling unit based on the first frame rate and the detected temperature of the imaging element to cool the imaging element.

[0019] In the method for controlling an imaging device according to the thirteenth aspect of the present invention, the imaging element preferably has sensitivity in the short-wave infrared band.

[0020] In the control method for an imaging device according to the 14th aspect of the present invention, it is preferable that the step of cooling the imaging element controls the cooling unit by setting a second temperature higher than a first temperature corresponding to the reference frame rate when the first frame rate is faster than a reference frame rate, and controls the cooling unit by setting a third temperature lower than the first temperature when the first frame rate is slower than the reference frame rate.

[0021] A fifteenth aspect of the invention is a control method for an imaging device that includes an imaging element having a photosensitive layer on a silicon substrate, a temperature detection unit that detects the temperature of the imaging element, and a processor, the control method for an imaging device including the steps of: the processor driving the imaging element at a first frame rate to capture time-series images; the temperature detection unit detecting the temperature of the imaging element; the processor determining the first frame rate based on the temperature of the imaging element detected by the temperature detection unit; and the processor driving the imaging element at the determined first frame rate. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a block diagram showing a first embodiment of an imaging device according to the present invention. [Figure 2]Figure 2 is a graph showing an example of the relationship between the frame rate [fps] that drives an image sensor sensitive to the SWIR band and the sensor sensitivity [V / W] for each sensor temperature. [Figure 3] FIG. 3 is a chart showing the numerical values ​​corresponding to the graph of FIG. [Figure 4] FIG. 4 is a graph showing another example of the relationship between the frame rate [fps] for driving an image sensor sensitive to the SWIR band and the sensor sensitivity [V / W] for each sensor temperature. [Figure 5] FIG. 5 is a chart showing the numerical values ​​corresponding to the graph of FIG. [Figure 6] FIG. 6 is a flowchart showing conditions for starting imaging. [Figure 7] FIG. 7 is a flowchart showing a first embodiment for controlling the cooling unit. [Figure 8] FIG. 8 is a flowchart showing a second embodiment for controlling the cooling unit. [Figure 9] FIG. 9 is a chart showing the relationship between the set frame rate and the target temperature. [Figure 10] FIG. 10 is a flowchart showing a third embodiment for controlling the cooling unit. [Figure 11] FIG. 11 is a block diagram showing a second embodiment of an imaging device according to the present invention. [Figure 12] FIG. 12 is a chart showing the frame rate to be set in accordance with the temperature of the image sensor. [Figure 13] FIG. 13 is a flow chart illustrating an embodiment for controlling the frame rate. [Figure 14] FIG. 14 is a block diagram of the main part of an imaging device in which the frame rate at which images are output is changed relative to the frame rate of the imaging element. [Figure 15] FIG. 15 is a timing chart showing the relationship between pixel reading from the image sensor and the output image. [Figure 16] FIG. 16 is a flowchart showing an embodiment of control when the frame rate for driving the image sensor and the frame rate for image output are different. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, preferred embodiments of an imaging device and a method for controlling an imaging device according to the present invention will be described with reference to the accompanying drawings.

[0024] [First embodiment of imaging device] FIG. 1 is a block diagram showing a first embodiment of an imaging device according to the present invention.

[0025] The imaging device 1-1 of the first embodiment shown in FIG. 1 includes a photographing lens 10, an imaging element 12, a cooling unit 14, a temperature detection unit 16, a CPU (Central Processing Unit) 26, a memory 28, an EVF (Electronic View Finder) 30, an LCD (Liquid Crystal Display) 32, and an operation unit 36.

[0026] The photographic lens 10 forms an image of subject light from a subject on the image sensor 12. The photographic lens 10 may be fixed to the main body of the image capturing device, or may be an interchangeable lens.

[0027] The imaging element 12 is an image sensor having a photosensitive layer on a silicon substrate, and is capable of acquiring images in the shortwave infrared band (SWIR band) by providing a photosensitive layer (photosensitive film) sensitive to the shortwave infrared (SWIR) band on a silicon substrate that has a readout circuit that can access two-dimensional addresses.

[0028] Next, the characteristics of an image sensor having sensitivity in the SWIR band will be described.

[0029] Figure 2 is a graph showing an example of the relationship between the frame rate [fps] that drives an image sensor sensitive to the SWIR band and the sensor sensitivity [V / W] for each sensor temperature.

[0030] 3 is a table showing the values ​​corresponding to the graph in FIG. 2. That is, the graph in FIG. 2 was created based on the values ​​in the table in FIG.

[0031] As shown in Figures 2 and 3, an image sensor sensitive to the SWIR band has the characteristic that the lower the frame rate at which the image sensor is driven, the higher the sensor sensitivity, and when the frame rate is lower than 30 fps, the sensor sensitivity increases exponentially.

[0032] Furthermore, even if the frame rate is the same, an image sensor that is sensitive to the SWIR band tends to have higher sensor sensitivity when the temperature of the image sensor is low, and this tendency is particularly noticeable when the frame rate is low.

[0033] Image sensors sensitive to the SWIR band have large noise caused by kTC noise (thermal noise) and dark current.

[0034] For example, it is known that when quantum dots are used to create a photosensitive region for wavelengths in the SWIR band, the spectral sensitivity characteristics change depending on the diameter of the quantum dots. Generally, the volume of an object changes with temperature, so the quantum dot diameter changes with temperature, and as a result, it is expected that the spectral sensitivity characteristics will depend on temperature. Therefore, in an image sensor that is sensitive to the SWIR band and has a quantum dot photosensitive film laminated on it, the sensitivity may change depending on the sensor temperature.

[0035] In order to maintain the desired sensor sensitivity (capturing low-noise images) in such an image sensor that has sensitivity in the SWIR band, it is effective to cool the image sensor and control the image frame rate.

[0036] FIG. 4 is a graph showing another example of the relationship between the frame rate [fps] for driving an image sensor sensitive to the SWIR band and the sensor sensitivity [V / W] for each sensor temperature.

[0037] 5 is a table showing the values ​​corresponding to the graph in FIG. 4. That is, the graph in FIG. 4 is created based on the values ​​in the table in FIG.

[0038] Another example shown in Figures 4 and 5 shows similar characteristics to the example shown in Figures 2 and 3, but differs from the characteristics shown in Figures 2 and 3 in that the sensor sensitivity also decreases when the frame rate decreases from 100 [fps] to 30 [fps] (when the frame rate decreases).

[0039] Therefore, when controlling the cooling of an image sensor having sensitivity in the SWIR band and the image capturing frame rate in order to maintain the desired sensor sensitivity, it is preferable to control the cooling and image capturing frame rate in accordance with the characteristics of the image sensor to be controlled.

[0040] 1, the cooling unit 14 cools the imaging element 12, and electrically cools it using, for example, a Peltier element. Various types of cooling unit 14 can be used, such as a cooler that uses a refrigerant.

[0041] The temperature detection unit 16 is a temperature sensor that detects the temperature of the imaging element 12, and converts the detected temperature into an electrical signal (temperature detection signal) and outputs it.

[0042] The CPU 26 is connected to a bus 27 .

[0043] In addition to the CPU 26, the bus 27 is connected to an interface (I / F) 20, a communication I / F 22, a memory 28, drivers 24, 34, and an operation unit 36, and the CPU 26 exchanges various control signals and data with each unit within the imaging device via the bus 27.

[0044] The CPU 26, which functions as a processor, controls each part of the imaging device in an integrated manner using a control program stored in the memory 28 or a memory within the CPU 26, and retrieves a processing program corresponding to each mode stored in the memory 28 or the like in response to a status signal from the operation unit 36, thereby executing each function of the imaging device 1-1.

[0045] The operation unit 36 ​​includes a power switch, a shutter release button, a shutter speed dial, an exposure compensation dial, a MENU / OK key, a cross key, a playback button, and the like.

[0046] The MENU / OK key is an operation key that functions both as a menu button for issuing a command to display a menu on the LCD 32 screen and as an OK button for issuing a command to confirm and execute a selection. The cross key is an operation unit for inputting commands in four directions (up, down, left, and right), and functions as a button for selecting an item from the menu screen and for issuing a command to select various setting items from each menu. The playback button is a button for switching to playback mode, which displays captured still images or videos on the LCD 32.

[0047] The CPU 26 also has a function of controlling the frame rate at which the image sensor 12 is driven and the cooling unit 14 .

[0048] The CPU 26 controls the cooling unit 14 based on the temperature of the imaging element detected by the temperature detection unit 16. A temperature detection signal is sent to the CPU 26 from the temperature detection unit 16 via the communication I / F 22, and the CPU 26 controls the cooling unit 14 via the driver 24 based on the target temperature set for the imaging element 12 and the temperature detection signal, thereby maintaining the temperature of the imaging element 12 at the target temperature. The control of the frame rate and the control of the cooling unit 14 by the CPU 26 will be described in detail below.

[0049] The communication I / F 22 outputs control signals such as an image read instruction signal and an imaging frame synchronization signal for controlling the imaging element 12 in response to commands from the CPU 26 to an I / F and signal control unit 18 within the imaging element 12. The I / F and signal control unit 18 controls the reading of image signals from the imaging element 12 based on the control signals input from the communication I / F 22. The I / F and signal control unit 18 also controls the timing of discharging (resetting) the electric charge accumulated in each pixel of the imaging element 12 based on an electronic shutter control signal input from the CPU 26 via the communication I / F 22, and performs electronic shutter control to adjust the period (exposure period) from when the electric charge is reset to when the image is read out in response to the imaging frame synchronization signal.

[0050] Furthermore, the I / F and signal control unit 18 includes an AFE (Analog Front End) circuit, which processes voltage signals (analog signals) corresponding to the charges accumulated during the exposure period and read from each pixel of the image sensor 12, and then outputs digital image data to the I / F 20. The AFE circuit includes a correlated double sampling circuit, an AGC (Automatic Gain Control) circuit, and an A / D (Analog-to-digital) converter.

[0051] The memory 28 includes a flash memory, a read-only memory (ROM), a random access memory (RAM), and the like.

[0052] The flash memory and ROM are non-volatile memories that store firmware, various programs including image processing software, image processing parameters, captured images (still images, video images), and the like.

[0053] The RAM functions as a work area for processing by the CPU 26, and also temporarily stores firmware and other programs stored in the non-volatile memory. Note that the CPU 26 may have part of the memory 28 (RAM) built in.

[0054] The CPU 26 also functions as a digital signal processing unit that performs various types of digital signal processing on image data that is temporarily stored in the memory 28 from the image sensor 12 via the I / F 20. That is, the CPU 26 performs digital signal processing such as offset processing, gain control processing including sensitivity correction, and gamma correction on the image data temporarily stored in the memory 28, stores the image data after digital signal processing back in the memory 28, and compresses the image data for recording and records an image file including the compressed data in non-volatile memory. Note that the above digital signal processing may be performed by a circuit dedicated to digital signal processing that is separate from the CPU 26.

[0055] The EVF 30 and LCD 32 display various images based on image data for display that is supplied from the CPU 26 via a driver 34 .

[0056] When displaying a live view image on the EVF 30 or LCD 32, the CPU 26 outputs image data that has been captured at a predetermined frame rate (e.g., 30 fps or 60 fps) and digitally signal processed to the display driver 34. The display driver 34 converts the input time-series image data into a signal format for display and outputs it sequentially to the EVF 30 or LCD 32. This allows the captured image to be displayed in real time on the EVF 30 or LCD 32. Note that when the user brings their eye close to the EVF 30 in shooting mode, an eye sensor (not shown) automatically switches the display to the EVF 30, and when the user moves their eye away, the display switches to the LCD 32.

[0057] The LCD 32 not only plays back and displays images that have been taken in the playback mode, but also functions as a display that displays various menu screens.

[0058] Next, the control of the cooling unit 14 during the imaging operation by the imaging device 1-1 having the above configuration will be described.

[0059] FIG. 6 is a flowchart showing conditions for starting imaging.

[0060] The imaging device 1-1 that captures images in the SWIR band captures high-sensitivity images for the inspection and monitoring of agricultural and industrial products, and mainly captures moving images, whether or not the captured moving images are recorded.

[0061] 2 to 5, the sensor sensitivity of an image sensor having sensitivity in the SWIR band changes depending on the temperature of the image sensor. The user sets a target temperature using the operation unit 36 ​​so that the sensor sensitivity required for inspection, etc. (low-noise images) can be obtained.

[0062] In FIG. 6, when the power switch is turned ON and imaging begins at the frame rate (first frame rate) that drives the image sensor 12, the CPU 26 determines whether the temperature of the image sensor 12 detected by the temperature detection unit 16 is lower than the set target temperature (step S10).

[0063] When the CPU 26 determines that the temperature of the image sensor 12 is lower than the target temperature (if "Yes"), it starts imaging because a low-noise image necessary for inspection etc. can be obtained (step S12).

[0064] If the CPU 26 determines that the temperature of the imaging element 12 is higher than the target temperature (if "No"), it ends the imaging without starting it.

[0065] In order to efficiently cool the imaging element 12, the driving of the imaging element 12 may be stopped until the imaging element 12 has cooled down to the target temperature. Since heat generation by the imaging element 12 is suppressed, the imaging element 12 can be cooled quickly.

[0066] <First embodiment for controlling the cooling unit> FIG. 7 is a flowchart showing a first embodiment for controlling the cooling unit 14.

[0067] In FIG. 7, the CPU 26 determines whether or not the temperature of the imaging element 12 detected by the temperature detection unit 16 after the start of imaging is lower than the target temperature (step S10).

[0068] If the CPU 26 determines that the temperature of the imaging element 12 is lower than the target temperature (if "Yes"), it weakens or suspends (stops) the cooling of the imaging element 12 by the cooling unit 14 (step S14).

[0069] This allows for more efficient control by stopping the cooling of the cooling unit 14 when the target temperature has been reached.

[0070] <Second embodiment for controlling the cooling unit> FIG. 8 is a flowchart showing a second embodiment for controlling the cooling unit 14.

[0071] When the imaging device 1-1 has a reference frame rate and drives the imaging element 12 at the reference frame rate, the CPU 26 controls the cooling unit 14 so that the temperature of the imaging element 12 becomes a temperature (first temperature) corresponding to the reference frame rate.

[0072] In FIG. 8, when the imaging device 12 is driven at a frame rate (first frame rate) different from the reference frame rate, the CPU 26 determines whether the first frame rate is faster (higher) than the reference frame rate (step S20).

[0073] If the CPU 26 determines that the first frame rate is faster than the reference frame rate (if "Yes"), it weakens the cooling of the image sensor 12 by the cooling unit 14 (step S22). That is, the CPU 26 controls the cooling unit 14 by setting the temperature (second temperature) higher than the first temperature corresponding to the reference frame rate.

[0074] On the other hand, if the CPU 26 determines that the first frame rate is slower (lower) than the reference frame rate (if "No"), it strengthens the cooling of the image sensor 12 by the cooling unit 14 (step S24). That is, the CPU 26 controls the cooling unit 14 by setting the temperature to a temperature (third temperature) lower than the first temperature corresponding to the reference frame rate.

[0075] As described above, in preparation for the case where the sensor sensitivity decreases during long exposure times (low frame rates) when the temperature of the image sensor 12 is high, efficient cooling control can be achieved by performing processing that strengthens cooling only when shooting at low frame rates and weakens cooling when shooting at high frame rates.

[0076] <Third embodiment for controlling the cooling unit> FIG. 9 is a chart showing the relationship between the set frame rate and the target temperature.

[0077] According to the chart shown in FIG. 9, the slower the frame rate, the lower the target temperature corresponding to that frame rate is set.

[0078] The memory 28 (first memory) stores target temperatures corresponding to frame rates as shown in FIG.

[0079] When the frame rate for driving the image sensor 12 is set, the CPU 26 acquires the corresponding target temperature from the memory 28 in accordance with the set frame rate, and controls the cooling unit 14 based on the acquired target temperature and the temperature of the image sensor 12 detected by the temperature detection unit 16.

[0080] FIG. 10 is a flowchart showing a third embodiment for controlling the cooling unit 14.

[0081] The flowchart shown in FIG. 10 sets the target temperature corresponding to the frame rate according to the chart in FIG.

[0082] 10, the CPU 26 determines whether the frame rate (first frame rate) at which the image sensor 12 is driven is less than 10 fps (step S30). If it is determined that the frame rate at which the image sensor 12 is driven is less than 10 fps, the CPU 26 sets the target temperature to 0°C (step S32).

[0083] If the frame rate at which the image sensor 12 is driven is 10 fps or more, the CPU 26 further determines whether it is less than 60 fps (step S34). If it is determined that the frame rate at which the image sensor 12 is driven is less than 60 fps (i.e., if it is determined that the frame rate is 10 fps or more but less than 60 fps), the CPU 26 sets the target temperature to 10°C (step S36).

[0084] If the frame rate at which the image sensor 12 is driven is 60 fps or higher, the CPU 26 sets the target temperature to 20° C. (step S36).

[0085] In step S32, step S36, or step S38, the CPU 26 controls the cooling unit 14 based on the target temperature set according to the frame rate and the temperature of the image sensor 12 detected by the temperature detection unit 16, so that the temperature of the image sensor 12 becomes the target temperature (step S39).

[0086] By setting a target temperature according to the frame rate, the cooling unit 14 can be controlled more precisely and efficiently.

[0087] In the flowchart shown in FIG. 10, the frame rate is set in three stages and the threshold is set to two values ​​(10 fps, 60 fps), but it goes without saying that the frame rate may be set in more detail.

[0088] [Second embodiment of imaging device] FIG. 11 is a block diagram showing a second embodiment of an imaging device according to the present invention.

[0089] In FIG. 11, parts common to the image pickup device 1-1 of the first embodiment shown in FIG. 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0090] An imaging device 1-2 of the second embodiment shown in FIG. 11 differs from the imaging device 1-1 of the first embodiment in that it does not include the cooling unit 14 and its driver 24 that are included in the imaging device 1-1 of the first embodiment.

[0091] The imaging device 1-2 of the second embodiment does not cool the imaging element 12, but controls the frame rate (first frame rate) at which the imaging element 12 is driven. That is, the CPU 26 of the imaging device 1-2 determines the frame rate at which the imaging element 12 is driven based on the temperature of the imaging element 12 detected by the temperature detection unit 16, and drives the imaging element 12 at the determined frame rate.

[0092] This makes it possible to obtain low-noise images required for inspections, etc., regardless of the temperature of the image pickup element 12.

[0093] <Embodiment for controlling frame rate> 2 to 5, the slower (lower) the frame rate is, the higher the sensor sensitivity of an image sensor that is sensitive to the SWIR band. On the other hand, for an image sensor that is sensitive to the SWIR band, the higher the temperature of the image sensor is, the lower the sensor sensitivity is, given the same frame rate.

[0094] Therefore, when the temperature of the image sensor rises, the frame rate at which the image sensor is driven is increased so that the sensor sensitivity (low-noise images) required for inspections and the like can be obtained.

[0095] FIG. 12 is a chart showing the frame rate to be set in accordance with the temperature of the image sensor.

[0096] According to the chart shown in FIG. 12, the higher the temperature of the imaging element, the faster (higher) the frame rate corresponding to that temperature is set.

[0097] The memory 28 (second memory) stores a frame rate (first frame rate) corresponding to the temperature of the image sensor 12 as shown in FIG.

[0098] The CPU 26 acquires a frame rate corresponding to the temperature from the memory 28 based on the temperature of the image sensor 12 detected by the temperature detection unit 16, and drives the image sensor 12 at the acquired frame rate.

[0099] FIG. 13 is a flow chart illustrating an embodiment for controlling the frame rate.

[0100] The flowchart shown in FIG. 13 operates the image sensor 12 at a frame rate corresponding to the temperature of the image sensor 12 in accordance with the chart in FIG.

[0101] 13, the CPU 26 determines whether the temperature of the imaging element 12 is below 10° C. (step S40). If it is determined that the temperature of the imaging element 12 is below 10° C., the CPU 26 operates the imaging element 12 at a frame rate of 10 fps (step S42).

[0102] If the temperature of the image sensor 12 is 10°C or higher, the CPU 26 further determines whether it is less than 30°C (step S44). If it is determined that the temperature of the image sensor 12 is less than 30°C (i.e., the temperature is determined to be 10°C or higher and less than 30°C), the CPU 26 operates the image sensor 12 at a frame rate of 60 fps (step S46).

[0103] If the temperature of the imaging element 12 is 30° C. or higher, the CPU 26 operates the imaging element 12 at a frame rate of 120 fps (step S48).

[0104] The camera has a temperature detection section 16 for detecting the temperature of the image pickup element 12, determines the frame rate of the image pickup from the detected temperature, and operates the image pickup element 12 at the determined frame rate, thereby making it possible to acquire a low-noise image.

[0105] In this way, the frame rate at which the image sensor 12 is driven is varied according to the temperature of the image sensor 12. In particular, when the temperature is high, the sensitivity decreases during long exposure times (low frame rates), so the frame rate is increased when the temperature rises, and decreased when the temperature drops, enabling long exposure times.

[0106] FIG. 14 is a block diagram of the main part of an imaging device in which the frame rate at which images are output is changed relative to the frame rate of the imaging element.

[0107] When the CPU 26 is set to output images at a frame rate (second frame rate) lower than the frame rate (first frame rate) of the image sensor 12, if the temperature of the image sensor 12 detected by the temperature detection unit 16 is equal to or higher than a reference temperature (e.g., 30°C), the CPU 26 adds frame images at the first frame rate and outputs images at the second frame rate.

[0108] 14, the CPU 26 varies the frame rate (first frame rate) at which the image sensor 12 is driven in accordance with the temperature of the image sensor 12 via the control I / F 21. In the example shown in Fig. 14, since the temperature of the image sensor 12 is 30°C or higher, the image sensor 12 is driven at a frame rate of 120 fps, and frame images of 120 fps are read out from the image sensor 12 and temporarily stored in the memory 28.

[0109] The CPU 26 processes the image data temporarily stored in the memory 28, and then outputs the image to the LCD 32 at a frame rate (second frame rate) different from the frame rate of the imaging element 12. In the example shown in Fig. 14, image data of 60 fps is output.

[0110] This is because the optimal frame rate (first frame rate) of the image sensor 12 is determined by the temperature of the image sensor 12, whereas the frame rate (second frame rate) of the image output to a display such as LCD 32 is determined by how the image is used.

[0111] FIG. 15 is a timing chart showing the relationship between pixel reading from the image sensor and the output image.

[0112] As shown in 15-1 of Figure 15, for example, the image sensor 12 is driven by a VD (Vertical Driving pulse) synchronization signal corresponding to 120 fps, and frame images are read out from the image sensor 12 at a frame rate of 120 fps in synchronization with the VD synchronization signal, as shown in 15-2 of Figure 15.

[0113] The frame images at a frame rate of 120 fps read out from the imaging element 12 are added together in groups of two frames, as shown in 15-3 of FIG. 15, and a frame image at a frame rate of 60 fps is output.

[0114] This not only allows the frame rate to be matched to the frame rate of the image output, but also allows the exposure time to be set to a substantially long time.

[0115] FIG. 16 is a flowchart showing an embodiment of control when the frame rate for driving the image sensor and the frame rate for image output are different.

[0116] In FIG. 16, the frame rate (first frame rate) for driving the image sensor 12 is set to S [fps], and the frame rate (second frame rate) for image output is set to I [fps] (step S50).

[0117] The CPU 26 determines whether the temperature of the image sensor 12 is below a reference temperature (10°C in this example) (step S52). If the temperature of the image sensor 12 is below 10°C ("Yes"), the CPU 26 further determines whether S>I (step S54).

[0118] If the CPU 26 determines in step S54 that S>I, it reduces S to I (step S56).

[0119] When the frame rate (I) of the image output of the imaging device 1-2 can be set, if the temperature of the imaging element 12 is low (less than 10°C), the frame rate (S) of the imaging element 12 is reduced to the frame rate (I) of the image output.

[0120] [others] In this embodiment, the hardware structure of a processing unit that executes various processes, such as the CPU 26 of the imaging device, is made up of various processors as follows: The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and functions as various processing units, a programmable logic device (PLD), such as an FPGA (Field Programmable Gate Array), whose circuit configuration can be changed after manufacture, and a dedicated electrical circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor having a circuit configuration designed specifically for executing specific processes.

[0121] A single processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types (for example, multiple FPGAs, or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor. Examples of multiple processing units configured with a single processor include, first, a configuration in which one processor is configured with a combination of one or more CPUs and software, as typified by client or server computers, and this processor functions as multiple processing units. Second, a configuration in which a processor is used to realize the functions of an entire system including multiple processing units on a single IC (Integrated Circuit) chip, as typified by a System on Chip (SoC). In this way, the various processing units are configured with one or more of the above-mentioned various processors as a hardware structure.

[0122] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit made up of a combination of circuit elements such as semiconductor elements.

[0123] Furthermore, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0124] 1-1, 1-2 Imaging device 10. Camera Lens 12 Image sensor 14 Cooling section 16 Temperature detection unit 18 I / F and signal control section 20 Interfaces 21 Control I / F 22 Communication I / F 24, 34 drivers 26 CPU 27 Bus 28 memory 30 EVF 32 LCD 36 Control section S10 Step S12 Step S14 Step S20 Step S22 Step S24 Step S30 Step S32 Step S34 Step S36 Step S38 Step S39 Step S40 Step S42 Step S44 Step S46 Step S48 Step S50 Step S52 Step S54 Step S56 Step

Claims

1. An imaging element having a photosensitive layer on a silicon substrate; a cooling unit that cools the imaging element; a temperature detection unit that detects the temperature of the imaging element; a processor, the processor controls the cooling unit based on a first frame rate at which the image sensor is driven and a temperature of the image sensor detected by the temperature detection unit; When the first frame rate is higher than a reference frame rate, the cooling unit is controlled by setting a second temperature higher than a first temperature corresponding to the reference frame rate, and when the first frame rate is lower than the reference frame rate, the cooling unit is controlled by setting a third temperature lower than the first temperature. Imaging device.

2. An imaging element having a photosensitive layer on a silicon substrate; a cooling unit that cools the imaging element; a temperature detection unit that detects the temperature of the imaging element; a first memory that stores a target temperature according to a frame rate; a processor, the processor controls the cooling unit based on a first frame rate at which the image sensor is driven and a temperature of the image sensor detected by the temperature detection unit; acquiring a corresponding target temperature from the first memory in accordance with the first frame rate, and controlling the cooling unit based on the acquired target temperature and the temperature of the image sensor detected by the temperature detection unit. Imaging device.

3. the processor weakens or suspends cooling of the imaging element by the cooling unit when the temperature of the imaging element detected by the temperature detection unit is lower than the target temperature; The imaging device according to claim 2 .

4. The imaging element is sensitive to a short-wave infrared band.

3. The imaging device according to claim 1.

5. the processor controls the cooling unit to perform cooling when the first frame rate is lower than a reference frame rate.

3. The imaging device according to claim 1.

6. An imaging element having a photosensitive layer on a silicon substrate; a temperature detection unit that detects the temperature of the imaging element; a processor, the processor determines a first frame rate based on the temperature of the image sensor detected by the temperature detection unit, and drives the image sensor at the determined first frame rate; In a setting in which images are output at a second frame rate lower than the first frame rate, when the temperature of the image sensor detected by the temperature detection unit is equal to or higher than a reference temperature, frame images at the first frame rate are added and images at the second frame rate are output. Imaging device.

7. An imaging element having a photosensitive layer on a silicon substrate; a temperature detection unit that detects the temperature of the imaging element; a processor, the processor determines a first frame rate based on the temperature of the image sensor detected by the temperature detection unit, and drives the image sensor at the determined first frame rate; In a setting in which images are output at a second frame rate lower than the first frame rate, when the temperature of the image sensor detected by the temperature detection unit is lower than a reference temperature, the first frame rate is reduced to the second frame rate. Imaging device.

8. a second memory configured to store the first frame rate according to the temperature of the imaging element; the processor acquires the corresponding first frame rate from the second memory based on the temperature of the image sensor detected by the temperature detection unit, and drives the image sensor at the acquired first frame rate.

8. The imaging device according to claim 6 or 7.

9. the processor drives the image sensor at the first frame rate to start capturing an image when the temperature of the image sensor detected by the temperature detection unit reaches a target temperature; 8. The imaging device according to claim 1, 2, 6 or 7.

10. A control method for an imaging device comprising: an imaging element having a photosensitive layer on a silicon substrate; a cooling unit that cools the imaging element; a temperature detection unit that detects the temperature of the imaging element; and a processor, comprising: the processor driving the image sensor at a first frame rate to capture time-series images; a step of detecting a temperature of the image sensor by the temperature detection unit; the processor controls the cooling unit based on the first frame rate and the detected temperature of the image sensor to cool the image sensor; the step of cooling the image sensor includes, when the first frame rate is higher than a reference frame rate, controlling the cooling unit to set a second temperature higher than a first temperature corresponding to the reference frame rate, and, when the first frame rate is lower than the reference frame rate, controlling the cooling unit to set a third temperature lower than the first temperature. A method for controlling an imaging device.

11. The imaging element is sensitive to a short-wave infrared band. The method for controlling an imaging device according to claim 10.

12. A control method for an imaging device including an imaging element having a photosensitive layer on a silicon substrate, a temperature detection unit that detects the temperature of the imaging element, and a processor, comprising: the processor driving the image sensor at a first frame rate to capture time-series images; a step of detecting a temperature of the image sensor by the temperature detection unit; a step of the processor determining the first frame rate based on the temperature of the image sensor detected by the temperature detection unit; the processor driving the image sensor at the determined first frame rate; When the temperature of the image sensor detected by the temperature detection unit is equal to or higher than a reference temperature in a setting in which the processor outputs images at a second frame rate lower than the first frame rate, the processor adds frame images at the first frame rate and outputs images at the second frame rate. A method for controlling an imaging device.

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