Image capture device, image capture device control method, and program

Abstract

To provide a small-sized imaging device with low power consumption, capable of detecting an abnormality in the insertion / removal state of an infrared cut filter.SOLUTION: An imaging device (100) includes an optical system (210), an imaging device (240) that photoelectrically converts an optical image formed by the optical system and outputs image data, an infrared cut filter (320), a filter holder (310) that includes a frame portion (312) and holds an infrared cut filter, a drive unit (340) that drives the filter holder such that the infrared cut filter can be inserted into and removed from an imaging optical path, and a control unit (501) that determines whether the insertion / removal state of the infrared cut filter is abnormal on the basis of the image data.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an imaging device, a control method for an imaging device, and a program. [Background technology]

[0002] Conventionally, imaging devices such as network cameras, which must provide users with stable images even in environments with large differences in brightness from daytime to nighttime, are equipped with an infrared cut filter to cut out infrared components that cause noise in images. To enable nighttime shooting using infrared LEDs, such imaging devices are equipped with an insertion / removal mechanism that allows the infrared cut filter to be inserted and removed. However, vibrations or impacts applied to the imaging device can prevent the infrared cut filter from being inserted or removed correctly. To address this issue, a detection mechanism, such as a photointerrupter or encoder, that detects the position of the infrared cut filter would increase power consumption and the imaging device's size.

[0003] Patent Document 1 discloses an imaging device that uses a devised light emission pattern of an infrared LED to detect the insertion / removal state of an infrared cut filter based on the signal strength of infrared light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-225073 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the imaging device disclosed in Patent Document 1 cannot detect abnormalities in the insertion or removal state of the infrared cut filter, such as when the infrared cut filter stops midway through the insertion or removal operation or when the position of the infrared cut filter is shifted.

[0006] Therefore, the present invention can provide an imaging device that is small and consumes low power, and that can detect abnormalities in the insertion / removal state of an infrared cut filter, a control method for an imaging device, and a program. [Means for solving the problem]

[0007] An imaging device according to one aspect of the present invention includes an optical system, an imaging element that photoelectrically converts an optical image formed by the optical system to output image data, an infrared cut filter, a filter holder that has a frame and holds the infrared cut filter, a drive unit that drives the filter holder so that the infrared cut filter can be inserted into or removed from a photographing optical path, and a control unit that determines whether or not the insertion / removal state of the infrared cut filter is abnormal based on the image data. The frame portion has a detection shape formed on the filter holder so as to penetrate the frame portion, and light from the optical system passes through the detection shape and is received by the image sensor. do.

[0008] Other objects and features of the present invention will be described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an imaging device that is small and consumes low power, and that is capable of detecting an abnormality in the insertion / removal state of an infrared cut filter, a control method for an imaging device, and a program. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an overall cross-sectional view of an imaging device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a detailed exploded view of a camera unit in the present embodiment. [Figure 3] 5A to 5C are explanatory diagrams illustrating the operation of the filter driving mechanism in the present embodiment. [Figure 4] 10 is a flowchart of an initialization operation of the filter driving mechanism in the present embodiment. [Figure 5] FIG. 2 is a block diagram of a control unit according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] First, a network camera (imaging device) in this embodiment will be described with reference to Fig. 1. Note that this embodiment will describe a network camera such as a surveillance camera or an in-vehicle camera as the imaging device, but the present invention is not limited to this and can also be applied to imaging devices other than network cameras.

[0013] FIG. 1 is an overall cross-sectional view of a network camera (imaging device) 100 according to this embodiment. The network camera 100 is capable of capturing and recording images. The network camera 100 has a housing, which is configured to include a cover unit 110 and a base unit 130. The cover unit 110 and the base unit 130 can each be made by molding a resin such as polycarbonate. Installation holes are formed in the base unit 130, and the cover unit 110 and the base unit 130 are fixed to a wall or vehicle using screws or the like. The cover unit 110 and the base unit 130 each have fastening units 120, which are fastened to each other using screws or the like.

[0014] The lens protection member 140 is hemispherical and serves to protect the lens (optical system) 210 and other components housed inside the housing from impact and dust. The lens protection member 140 is fixed to the cover unit 110 by ultrasonic welding or other methods. When capturing an image, the lens protection member 140 is treated as an optical component because it is captured through the lens protection member 140. Therefore, transparency and dimensional accuracy are important. The lens protection member 140 is made of, for example, transparent polycarbonate. The cover unit 110 has a window 160 for emitting infrared LED light. Irradiating the infrared LED enables capturing images even in dark environments, such as at night. The window 160 is color-tuned to block visible light and transmit infrared light. This prevents the components inside the housing from being seen from the outside. The wavelength of infrared light is generally approximately 750 nm to 950 nm. The inside of the housing of the window 160 has a lens shape, which can focus or diffuse the light from the infrared LED. The window 160 is integrally molded with the cover portion 110 and is made of, for example, black transparent polycarbonate.

[0015] The housing contains the camera unit 200, gasket 180, circuit board 500, infrared LED 520, and holding member 280. The gasket 180 is positioned in a pressed state at the boundary between the cover unit 110 and the base unit 130. Pressing the gasket 180 increases the adhesion of the gasket 180 to the housing, providing sealing performance. This is the same as the sealing structure of an O-ring. The lens protection member 140, window 160, and gasket 180 form a sealed structure for the housing, preventing water and dust from entering the housing. The gasket 180 is roughly diamond-shaped and is configured to generate little reaction force when pressed. The gasket 180 is made of, for example, silicone rubber.

[0016] The camera unit 200 is disposed approximately in the center of the housing and includes a lens 210, a lens holder 230, an image sensor 240, an image sensor board 242 on which the image sensor 240 is mounted, an infrared cut filter unit 300, a lens cover 250, and a camera holder 260. The lens 210 is screwed and held in the lens holder 230, and is configured as a fixed focal length lens whose position can be adjusted in the optical axis direction to adjust the focus. The image sensor board 242 is fixed to the infrared cut filter unit 300 with adhesive or screws. The lens holder 230 and the lens cover 250 are held so as to be covered by the camera holder 260 and the base unit 130, and are capable of tilting and rotating.

[0017] An opening for capturing an image is formed in the front of the lens holder 230. A hole for passing a wire or the like is formed in the rear of the lens cover 250. The lens holder 230 can be made by, for example, metal die-casting or molding a resin such as polycarbonate. The camera holder 260 has a continuous opening from a substantially horizontal position to a substantially vertical position, which is the shooting range. The camera holder 260 also regulates the range of tilt movement. The camera holder 260 can be made by, for example, molding a resin such as polycarbonate.

[0018] Holding member 280 holds camera unit 200 via camera holder 260 so that it can pan and rotate, and is fixed to base unit 130 using screws or the like. The direction of the pan rotation axis is approximately perpendicular to the installation surface. Holding member 280 can be made by molding a resin such as polycarbonate.

[0019] The housing also houses a circuit board 500. The circuit board 500 has an opening in the center, where the camera unit 200 is disposed. An infrared LED 520 is also mounted on the circuit board 500. The circuit board 500 has a control unit 501 such as a CPU, and is responsible for overall control of the network camera 100, including control of the infrared cut filter unit 300 and the infrared LED 520, power supply, camera control, and connection to the network. The circuit board 500 and the imaging board 242 are electrically connected by a wire (not shown) or the like.

[0020] Next, the configuration of the camera unit 200 will be described in detail with reference to FIG. 2. FIG. 2 is a detailed exploded view of the camera unit 200. In the camera unit 200, light passing through the lens 210 passes through the infrared cut filter unit 300 and is received by the image sensor 240. The image sensor 240 is a photoelectric conversion element such as a CMOS sensor or a CCD sensor, which photoelectrically converts the optical image formed by the lens 210 and outputs an electrical signal (image data) to the circuit board 500. The image sensor 240 is mounted on the lens 210 side of the image sensor board 242. The circuit board 500 records the received image data or distributes it over a network. An orientation detection unit 244 is mounted on the image sensor board 242. The orientation detection unit 244 is, for example, an acceleration sensor. In vehicle applications, the acceleration sensor can be used to detect strong vibrations or impacts on the network camera 100 and determine sudden braking or a collision. Since the acceleration sensor can detect the direction of gravity, it can also detect the orientation in which the network camera 100 is installed. The direction detection means 244 can define (detect) a defined axial direction (predetermined direction) based on the direction of gravity.

[0021] The infrared cut filter unit 300 includes a filter holder 310, an infrared cut filter 320, a glass filter 330, a low-reflectivity section 370, a filter drive mechanism (drive section) 340, a holder base 360, and a holder cover 350. The infrared cut filter unit 300 is fixed to the lens holder 230 with screws or the like. The filter holder 310 holds the infrared cut filter 320 and the glass filter 330 so as to cover their edges, and the infrared cut filter 320 and the glass filter 330 are fixed in place by adhesive or thermal caulking. The infrared cut filter 320 blocks infrared light exceeding approximately 700 nm. Conversely, the glass filter 330 transmits light in a wide wavelength range, including infrared light.

[0022] The filter holder 310 has a frame 312 between the infrared cut filter 320 and the glass filter 330. The longitudinal direction of the frame 312 coincides with an axis defined by the orientation detection means 244. The frame 312 has a detection shape 314 formed therein, which is formed as a through-hole to allow light to pass through. The filter holder 310 is drivably held by a holder base 360 ​​and a holder cover 350. The filter holder 310, holder base 360, and holder cover 350 are made by molding a resin such as polycarbonate. A low-reflection portion 370 is fixed to the filter holder 310 on the imaging element 240 side with double-sided tape or the like. The low-reflection portion 370 has a through-hole 372 that allows light to pass through, at a position corresponding to the detection shape 314 of the frame 312. The low-reflection portion 370 is preferably made of a material with a reflectance of 5% or less.

[0023] The filter drive mechanism 340 drives the filter holder 310 so that the infrared cut filter 320 can be inserted into or removed from the imaging optical path. In this embodiment, the filter drive mechanism 340 is composed of, for example, a stepping motor and gears, and drives the filter holder 310 to a first position where the infrared cut filter 320 enters the imaging optical path, and to a second position where the glass filter 330 enters the imaging optical path. When the network camera 100 is powered on, the filter drive mechanism 340 calibrates the initial position by abutting the filter holder 310 against the drive end on the first position side. Thereafter, the filter drive mechanism 340 controls the amount of movement of the filter holder 310 by driving the stepping motor a predetermined number of pulses using PDM control of the stepping motor.

[0024] During the day or when the shooting environment is bright due to lighting, the network camera 100 captures images in a first position where the infrared cut filter 320 is inserted into the shooting optical path. Sunlight and illumination light contain many infrared components that are difficult for the human eye to see. Generally, the infrared components of light often become noise components in images. Therefore, inserting the infrared cut filter 320 can remove the infrared components of light and provide images with less noise. On the other hand, at night or in a dark indoor environment, when lighting visible to the human eye is not available, it is necessary to turn on the infrared LED 520 to brightly illuminate the shooting area. The image sensor 240 can also receive infrared components that are difficult for the human eye to see. Therefore, turning on the infrared LED 520 makes it possible to capture images even in dark environments. In this case, the network camera 100 captures images in a second position where the glass filter 330 is inserted into the shooting optical path, allowing infrared components to pass through, enabling capture in dark places.

[0025] Next, with reference to Figures 3(a) to 3(c), the operation of the filter drive mechanism 340 will be described. Figures 3(a) to 3(c) are explanatory diagrams of the operation of the filter drive mechanism 340, and show states a to c of the filter drive mechanism 340, respectively.

[0026] State a is a state (second state) corresponding to a second position where the glass filter 330 is inserted into the imaging optical path, such as at night. The dotted frame (imaging range 600a) is the actual imaging range. As shown in FIG. 3(a), in state a, the filter holder 310 is moved to the left end by the filter drive mechanism 340. At this time, there is nothing blocking the optical path within the imaging range 600a, so a good image can be provided. State c is a state (first state) corresponding to a first position where the infrared cut filter 320 is inserted into the imaging optical path, such as during the day. As shown in FIG. 3(c), in state c, the filter holder 310 is moved to the right end. In state c, as in state a, there is nothing blocking the optical path within the imaging range 600c.

[0027] When the network camera 100 is used in a vehicle or is subjected to strong vibrations, the infrared cut filter unit 300 may not operate normally. For example, as shown in state b in FIG. 3(b), the operation of the filter holder 310 may stop midway or the position may gradually shift. In state b, the frame 312 of the filter holder 310 is within the shooting range 600b. In this case, the frame 312 appears in the captured image (the image data includes an area corresponding to the frame 312), and it may not be possible to provide an appropriate image. For this reason, if the position of the filter holder 310 is incorrect, it is necessary to return the filter holder 310 to its normal position.

[0028] As mentioned above, the filter drive mechanism 340 performs position calibration of the filter holder 310 when the network camera 100 is powered on, and therefore does not always know the position of the filter holder 310. As a result, the network camera 100 cannot detect operational abnormalities in the filter drive mechanism 340. To constantly detect the position of the filter holder 310, it is necessary to use a separate position detection means such as a photointerrupter or encoder. However, using a dedicated position detection means increases the size of the infrared cut filter unit 300 and power consumption.

[0029] Therefore, in this embodiment, the frame portion 312 that is within the imaging range 600 (600a to 600c) is used to perform an initialization operation of the filter driving mechanism 340. Specifically, the frame portion 312 is detected based on image data acquired by the imaging element 240, and the initialization operation is performed based on several determination steps that will be described later.

[0030] To improve the detection accuracy of the frame 312, the frame 312 is formed with multiple detection shapes: a substantially circular detection shape 314, a detection shape 316 on the infrared cut filter 320 side, and a detection shape 318 on the glass filter 330 side. The detection shapes 314, 316, and 318 are each formed with a through-hole shape and allow light to pass through. The detection shape 316 passes light that has passed through the infrared cut filter 320, and the detection shape 318 passes light that has passed through the glass filter 330. In this embodiment, the detection shapes 314, 316, and 318 are arranged asymmetrically in the longitudinal direction of the frame 312, centered on the optical axis of the lens 210. Because the lens 210 is a fixed-focus lens, the size of the optically recognizable shape can be calculated from the focal length. Each detection shape is equal to or larger than its optically recognizable size.

[0031] Next, the initialization operation of the filter driving mechanism 340 will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a flowchart of the initialization operation of the filter driving mechanism 340. Each step in Fig. 4 is executed by a control unit 501 provided on a circuit board 500. Fig. 5 is a block diagram of the control unit 501.

[0032] First, in step S1, the area determination means 501a determines whether or not a low-brightness area has been detected in the image (image data) obtained from the image sensor 240, extending from one end of the image data to the other (low-brightness area detection step). That is, the area determination means 501a determines whether or not a low-brightness area in the image data exists from a first end of the image data to a second end opposite the first end (across both ends). The low-brightness area is an area located on the image sensor 240 side of the frame portion 312, and is an area with low brightness due to the effect of the low-reflectivity portion 370. Furthermore, since the frame portion 312 is substantially rectangular and is disposed in an area larger than the imaging range of the image sensor 240, the low-brightness area reaches the end of the image data. If a low-brightness area is detected in step S1, the process proceeds to step S2. On the other hand, if a low-brightness area is not detected, the process repeats the determination in step S1.

[0033] In step S2, the direction determination means 501b determines whether the longitudinal direction of the low-brightness region coincides with the direction specified by the orientation detection means 244 (direction determination step). In step S2, it is determined whether one axis of the acceleration sensor used as the orientation detection means 244 coincides with the longitudinal direction of the frame portion 312, thereby determining whether the low-brightness region corresponds to the frame portion 312 or another object. For example, if an object such as a telephone pole or tree exists from one end of the image to the other, and the direction of the object differs from the longitudinal direction of the frame portion 312, it is determined that the object is not a low-brightness region. If these directions coincide in step S2, the process proceeds to step S3. On the other hand, if these directions do not coincide, the process returns to step S1.

[0034] In step S3, the shape determination means 501c determines whether or not a detection shape 314 has been detected in the low-brightness area (shape detection step). In step S3, the shape pattern present in the low-brightness area is compared with the pattern of the detection shape 314 pre-stored in the network camera 100 to determine whether or not the low-brightness area is a frame 312. If a detection shape 314 is detected in the low-brightness area in step S3, the process proceeds to step S4. On the other hand, if a detection shape 314 is not detected in the low-brightness area, the process returns to step S1.

[0035] In step S4, the image difference determination means 501d determines whether the color difference or brightness difference (image difference, i.e., the difference in pixel values) between the two regions separated by the frame portion 312 is equal to or greater than a certain value (image difference determination step). The light passing through the infrared cut filter 320 and the light passing through the glass filter 330 have different infrared components, resulting in a large color difference. Specifically, the light passing through the glass filter 330 contains a large infrared component, resulting in a strong red color. Furthermore, since the infrared LED 520 is turned on at night, the light passing through the infrared cut filter 320 appears dark, while the light passing through the glass filter 330 appears bright, resulting in a large brightness difference. Using this fact, it is determined whether a low-brightness region in the image data corresponds to the frame portion 312. If the color difference or brightness difference between the two regions is equal to or greater than the certain value in step S4, the process proceeds to step S5. On the other hand, if the color difference or brightness difference between the two regions is smaller than the certain value, the process returns to step S1.

[0036] If it is determined based on the results of steps S1 to S4 that the low-brightness region corresponds to the frame portion 312, then in step S5 the control unit 501 performs an initialization operation of the filter driving mechanism 340. Note that the initialization operation in step S5 may be performed only if the state in which it has been determined that the low-brightness region corresponds to the frame portion 312 continues for a certain period of time.

[0037] Next, in step S6, the control unit 501 starts normal shooting. That is, in a bright shooting environment, shooting is performed at a first position (first state) where the infrared cut filter 320 is inserted into the shooting optical path. On the other hand, in a dark shooting environment, shooting is performed at a second position (second state) where the glass filter 330 is inserted into the shooting optical path. The control unit 501 then continues to determine whether or not the filter driving mechanism 340 is operating normally, based on the image data. Note that in this embodiment, it is not essential to make determinations in all steps S1 to S4, and it may be determined whether or not to perform the initialization operation based on the determination result in at least one of steps S1 to S4.

[0038] In this embodiment, the control unit 501 determines whether the insertion / removal state of the infrared cut filter 320 is abnormal (a state in which the infrared cut filter 320 has stopped midway through the insertion / removal operation or a state in which the position of the infrared cut filter 320 has shifted) based on the image data. Preferably, the control unit 501 determines that the insertion / removal state is abnormal when it detects an area corresponding to the frame portion 312 in the image data. Also preferably, the control unit 501 determines that the insertion / removal state is abnormal when the color difference or luminance difference between at least two areas in the image data is equal to or greater than a predetermined value. Also preferably, when it determines that the insertion / removal state is abnormal, the control unit 501 performs an initialization operation of the filter drive mechanism 340. More preferably, the control unit 501 performs the initialization operation when the insertion / removal state abnormality continues for a predetermined time.

[0039] As a result, even if an abnormality occurs in the insertion / removal operation of the filter drive mechanism due to vibration or impact in the vehicle, a stable image can be provided to the user by performing an initialization operation without having to provide a dedicated part for detecting the position of the filter part.

[0040] In this embodiment, the filter drive mechanism 340 is composed of a stepping motor and gears, but other drive mechanisms such as a galvanometer motor or a brushless motor may also be used. In this embodiment, the detection shape 314 is generally circular, but may be of any other shape as long as it is large enough to transmit light and be optically recognizable. In this embodiment, the infrared cut filter 320 and the glass filter 330 may be fixed using screws or other components. In this embodiment, the orientation detection means 244 may be other sensors, such as a gyro sensor or an optical direction detection sensor. In this embodiment, the low-reflection portion 370 may be formed by surface treatment, such as embossing or painting, on the surface of the frame 312. In this embodiment, the infrared cut filter 320 cuts infrared light at a wavelength of approximately 700 nm, but other wavelengths may be used depending on the application.

[0041] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a 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., ASIC) that realizes one or more functions.

[0042] According to this embodiment, even if an abnormality occurs in the insertion / removal operation of the infrared cut filter due to vibration or impact, it is possible to perform an initialization operation without using a means for detecting the position of the infrared cut filter, and to provide a stable image to the user. Therefore, according to this embodiment, it is possible to provide an imaging device, a control method for an imaging device, and a program that are low-power and small in size and capable of detecting an abnormality in the insertion / removal state of the infrared cut filter.

[0043] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0044] 100 Network camera (imaging device) 210 Lens (optical system) 240 image sensor 310 Filter Holder 312 Frame 320 Infrared cut filter 340 Filter drive mechanism (drive unit) 501 Control section

Claims

1. An optical system; an imaging element that photoelectrically converts an optical image formed by the optical system and outputs image data; An infrared cut filter, a filter holder having a frame portion and holding the infrared cut filter; a drive unit that drives the filter holder so that the infrared cut filter can be inserted into or removed from the photographing optical path; a control unit that determines whether or not the insertion / removal state of the infrared cut filter is abnormal based on the image data, the frame portion has a detection shape formed on the filter holder so as to penetrate the frame portion, An imaging device, characterized in that light from the optical system passes through the detection shape and is received by the imaging element.

2. 2. The imaging device according to claim 1, wherein the control unit determines that the insertion / removal state is abnormal when a region corresponding to the frame portion is detected in the image data.

3. 3. The imaging device according to claim 1, wherein the control unit determines that the insertion / removal state is abnormal when a color difference or a luminance difference between at least two regions in the image data is equal to or greater than a predetermined value.

4. The filter holder further includes a glass filter held by the filter holder.

4. The imaging device according to claim 1, wherein the frame portion is disposed between the infrared cut filter and the glass filter.

5. 5. The imaging device according to claim 1, wherein the control unit performs an initialization operation of the drive unit when it determines that the insertion / removal state is abnormal.

6. 6. The imaging device according to claim 5, wherein the control unit performs the initialization operation when the abnormality in the insertion / removal state continues for a predetermined time.

7. the detection feature includes a plurality of feature portions; 7. The imaging device according to claim 1, wherein the plurality of shaped portions are arranged asymmetrically in the longitudinal direction of the frame portion with the optical axis of the optical system as the center.

8. one of the plurality of shaped portions transmits light that has passed through the infrared cut filter; 8. The imaging device according to claim 7, wherein another one of the plurality of shaped portions transmits light that has passed through a glass filter.

9. 9. The imaging device according to claim 1, wherein the frame portion is provided with a low-reflection portion having a reflectance of 5% or less.

10. 10. The imaging device according to claim 9, wherein the low-reflectivity portion has a through-hole formed at a position corresponding to the detection shape.

11. A control method for an imaging device capable of inserting and removing an infrared cut filter held by a filter holder having a frame portion into and from an imaging optical path, comprising: an acquisition step of acquiring image data by photoelectrically converting an optical image formed by the optical system; a determining step of determining whether or not the insertion / removal state of the infrared cut filter is abnormal based on the image data, the frame portion has a detection shape formed on the filter holder so as to penetrate the frame portion, A method for controlling an imaging device, wherein light from the optical system passes through the detection shape and is received by an imaging element.

12. 12. The method for controlling an imaging device according to claim 11, wherein the determining step includes a step of determining whether or not a low-brightness area of ​​the image data exists from a first end to a second end of the image data.

13. 13. The method for controlling an imaging device according to claim 11, wherein the determining step includes a step of determining whether or not a longitudinal direction of a low-brightness area of ​​the image data coincides with a longitudinal direction of the frame portion.

14. 14. The control method for an imaging device according to claim 11, wherein the determination step includes a step of determining whether or not a detection shape formed in the frame portion is detected in a low-brightness area of ​​the image data.

15. 15. The method for controlling an imaging device according to claim 11, wherein the determining step includes a step of determining whether a color difference or a brightness difference between at least two areas in the image data is equal to or greater than a certain value.

16. A program causing a computer to execute the control method according to any one of claims 11 to 15.

Images