Imaging apparatus and control method for imaging apparatus

Abstract

To provide an imaging apparatus capable of more efficiently suppressing damage of a shutter or an imaging section in a case where strong light is incident to the imaging apparatus.SOLUTION: An imaging apparatus (1) comprises: an imaging section (3) which picks up a thermal image; a lens section (2) which guides light (L) to be imaged by the imaging section (3) to the imaging section (3); a drive section (5) which moves at least a part of the lens section (2) in an optical axis direction; a shutter (4) which is disposed between the lens section (2) and the imaging section (3); and a control section (6) which controls the drive section (5) in such a manner that a focal position (P1) of the light (L) moves in the optical axis direction with respect to a reference focal position (P2) focusing the light (L) onto a light incidence plane (3a) of the imaging section (3) based on a surface temperature of the shutter (4) derived based on a picked-up image obtained by imaging the shutter (4) in a closed state by means of the imaging section (3).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an imaging device and a control method for the imaging device. [Background technology]

[0002] In an imaging device, strong light such as sunlight may directly enter the imaging section, which may damage the imaging section. Therefore, for example, the imaging device of Patent Document 1 is configured to move the lens group to the closest position when the imaging device transitions to an inoperative state, thereby suppressing damage to the imaging section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-62833 A Summary of the Invention [Problem to be solved by the invention]

[0004] The imaging device of Patent Document 1 has a problem in that it is not possible to prevent damage to the shutter and the imaging section when strong light is incident on the imaging device while the imaging device is in an operating state.

[0005] An object of the present disclosure has been made to solve, for example, the above-mentioned problems, and to realize an imaging device and a control method for an imaging device that can more efficiently suppress damage to the shutter and imaging unit when strong light is incident on the imaging device. [Means for solving the problem]

[0006] An imaging device according to an embodiment of the present disclosure includes: An imaging unit that captures a thermal image; a lens unit for guiding light captured by the imaging unit to the imaging unit; a drive unit that moves at least a part of the lens unit in the optical axis direction; a shutter disposed between the lens unit and the imaging unit; a control unit that controls the drive unit based on a surface temperature of the shutter derived based on an image captured by the imaging unit of the shutter in a closed state, so that a focusing position of the light moves in the optical axis direction with respect to a reference focusing position where the light is focused on a light incident surface of the imaging unit; and Equipped with.

[0007] A method for controlling an imaging device according to an embodiment of the present disclosure includes: a step of acquiring a captured image by causing the imaging unit to capture an image of the shutter, the shutter being disposed between the imaging unit and a lens unit for guiding light captured by the imaging unit to the imaging unit, in a closed state; a step of moving at least a part of the lens unit in an optical axis direction based on a surface temperature of the shutter derived based on the captured image, thereby moving a focusing position of the light in the optical axis direction with respect to a reference focusing position where the light is focused on a light incident surface of the image capturing unit; Equipped with. Effect of the Invention

[0008] According to the present disclosure, it is possible to realize an imaging device and a control method for an imaging device that can more efficiently prevent damage to the shutter and imaging section when strong light is incident on the imaging device. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a state in which a light collecting position is disposed on a light incident surface of an imaging unit in an imaging device according to an embodiment; [Diagram 2] 2 is a block diagram showing a configuration of a control system of the imaging apparatus according to the embodiment; [Diagram 3] FIG. 4 is a flowchart showing the flow of a control method for the imaging device according to the embodiment. [Figure 4] 11A and 11B are diagrams illustrating a state in which the light collecting position has moved in the light incident direction in the imaging device according to the embodiment. [Diagram 5] 1 is a diagram showing a captured image obtained by capturing an image of the shutter in a closed state with an imaging section; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, specific embodiments to which the present disclosure is applied will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments, and the following description and drawings are appropriately simplified.

[0011] Fig. 1 is a diagram showing a state in which the light collecting position is arranged on the light incident surface of the imaging unit in the imaging device of this embodiment. Fig. 2 is a block diagram showing the configuration of a control system of the imaging device of this embodiment. The imaging device 1 of this embodiment is suitable as, for example, a far-infrared camera mounted on a vehicle. As shown in Figs. 1 and 2, the imaging device 1 includes a lens unit 2, an imaging unit 3, a shutter 4, a drive unit 5, and a control unit 6.

[0012] In the following description, for clarity, a three-dimensional (XYZ) coordinate system is used. As shown in Fig. 1, the direction in which the optical axis AX of light L incident on the imaging device 1 extends (i.e., the optical axis direction) is parallel to the Y axis, and the light L is incident on the imaging device 1 from the negative side of the Y axis toward the positive side of the Y axis.

[0013] 1, the lens unit 2 includes a first lens 2a and a second lens 2b to guide the light L to the imaging unit 3. The first lens 2a is, for example, a plano-convex lens having a plane substantially parallel to the XZ plane on the surface on the Y-axis + side of the first lens 2a and a convex surface convex toward the Y-axis - side on the surface on the Y-axis - side of the first lens 2a. The first lens 2a is, for example, fixed inside a housing (not shown) of the imaging device 1.

[0014] As shown in FIG. 1, the second lens 2b is disposed on the +Y-axis side with respect to the first lens 2a. That is, the second lens 2b is disposed at a position closer to the imaging unit 3 than the first lens 2a. The second lens 2b is, for example, a concave meniscus lens having a concave surface on the +Y-axis side of the second lens 2b and a convex surface on the -Y-axis side of the second lens 2b. The second lens 2b is, for example, provided inside the housing of the imaging device 1 so as to be movable in the Y-axis direction via the drive unit 5. The configuration of the lens unit 2 described above is an example and is not limited thereto. For example, the lens may be one piece, or the first lens 2a or the second lens 2b may be an aspheric lens.

[0015] As shown in Fig. 1, the imaging unit 3 is disposed on the + side of the Y axis with respect to the lens unit 2. The imaging unit 3 includes a sensor that captures a thermal image. The sensor included in the imaging unit 3 is, for example, a microbolometer, and is composed of thermal elements arranged in a matrix, and the thermal elements detect far-infrared rays. The imaging unit 3, and in turn the light incident surface 3a of the sensor, are disposed facing the - side of the Y axis.

[0016] 1, the shutter 4 is disposed between the lens unit 2 and the imaging unit 3 in the Y-axis direction. The shutter 4 may be configured to block light L from entering the light incident surface 3a (i.e., the surface on the Y-axis negative side) of the imaging unit 3, and may be configured as a general so-called mechanical shutter.

[0017] 1, the shutter 4 is configured to cover substantially the entire light incident surface 3a of the imaging unit 3. The first lens 2a, the second lens 2b, the imaging unit 3, and the shutter 4 are disposed on the optical axis AX.

[0018] The driving unit 5 is an actuator that moves at least a part of the lens unit 2 in the optical axis direction, for example, moving the second lens 2b in the Y-axis direction. The driving unit 5 includes, for example, a moving mechanism that moves the second lens 2b in the Y-axis direction, and a motor connected to the moving mechanism so as to be able to transmit a driving force. The driving unit 5 may be configured to be capable of moving the second lens 2b in the Y-axis direction, for example, and may be configured with a mechanism that is used in general imaging devices.

[0019] As shown in FIG. 2, the control unit 6 controls the imaging unit 3, the shutter 4, and the driving unit 5. As will be described in detail later, the control unit 6 controls the shutter 4 to close in order to prevent damage to pixels in an area where a high-temperature object such as sunlight is photographed by the imaging device 1. Meanwhile, the microbolometer is calibrated (corrected image data) in order to suppress deterioration of the accuracy of temperature detection. One common calibration method is to adjust the output of the microbolometer with the shutter 4, which is a black body, closed (so-called mechanical shutter correction). The mechanical shutter correction includes a process of closing the shutter 4 periodically or intermittently. In other words, the control unit 6 controls the opening and closing of the shutter 4 when performing the mechanical shutter correction.

[0020] Here, when the imaging device 1 is in a normal state with the shutter 4 open, rather than when a high-temperature object is being photographed, the control unit 6 controls the drive unit 5 so that the light L is collected on the light incident surface 3a of the imaging unit 3. The light collection position P1 in such a normal state is set as a reference light collection position P2.

[0021] The control unit 6 derives the surface temperature of the shutter 4 based on an image of the shutter 4 in a closed state, which is obtained by controlling the imaging unit 3, and controls the drive unit 5 so that the focusing position P1 of the light L moves in the Y-axis direction based on the derived surface temperature of the shutter 4.

[0022] Next, the flow of the control method of the imaging device 1 of this embodiment will be described. Fig. 3 is a flow chart showing the flow of the control method of the imaging device of this embodiment. Fig. 4 is a diagram showing a state in which the light collecting position has moved in the light incident direction in the imaging device of this embodiment. Fig. 5 is a diagram showing a captured image obtained by capturing an image of the shutter in a closed state by the imaging section.

[0023] Here, it is assumed that the imaging device 1 is in a normal state. In other words, it is assumed that the imaging unit 3 generates an image based on the light L incident on the imaging unit 3 in a state where the shutter 4 is open and the light collection position P1 of the light L is located at the reference light collection position P2. It is also assumed that the imaging unit 3 continues to capture images in an operating state where the imaging device 1 is in either a normal state or a state where a high-temperature object is being photographed.

[0024] In this state, the control unit 6 judges whether the imaging device 1 is photographing a high-temperature object based on the captured image (step S1). In detail, the imaging unit 3 receives infrared light incident on each pixel of the imaging unit 3, and generates a captured image by a change in the resistance value of each heat-sensitive element. If the captured image includes a range of pixels whose average resistance value is equal to or greater than a first threshold value, that is, if the captured image includes a range of pixels that have captured an image of a high-temperature object such as sunlight, the control unit 6 judges that the imaging device 1 is photographing a high-temperature object. Here, the range of pixels that have captured an image of a high-temperature object is referred to as a first range in the following description.

[0025] The first range may be one pixel of the imaging unit 3, any number of pixels, a number of pixels within a predetermined range, or all pixels. The first threshold value may be set to a resistance value slightly lower than the resistance value at which the captured image is overexposed and becomes overexposed. For example, when the resistance value is expressed in 14 bits, the lower limit is zero, and the upper limit is 3fff, the first threshold value is about 3ffd. However, the first threshold value may be set to a resistance value that can suppress damage to the light incident surface 3a of the imaging unit 3. For example, the upper limit of the resistance value, 3fff, may be set to the first threshold value.

[0026] When the control unit 6 does not determine that a high-temperature object is being photographed, for example, when the captured image does not include the first range (NO in step S1), the control unit 6 returns to the process of step S1. More specifically, when the captured image does not include a range of pixels whose average resistance value is equal to or greater than the first threshold value. On the other hand, when the control unit 6 determines that a high-temperature object is being photographed, for example, when the captured image includes the first range (YES in step S1), the control unit 6 controls the shutter 4 to close the shutter 4 (step S2). More specifically, when the captured image includes a range of pixels whose average resistance value is equal to or greater than the first threshold value. As a result, when light L, such as sunlight, that may cause an abnormality in the imaging unit 3 when captured, is incident on the imaging device 1, the light L is blocked from entering the light incident surface 3a of the imaging unit 3, and damage to the imaging unit 3 can be suppressed.

[0027] Next, when the imaging unit 3 closes the shutter 4 due to capturing an image of a high-temperature object, the control unit 6 derives the surface temperature of the shutter 4 based on a captured image of the shutter 4 in a closed state captured by the imaging unit 3 (step S3). That is, the control unit 6 derives the surface temperature of the shutter 4 based on the resistance value of each pixel corresponding to the imaging area of ​​the shutter 4 in the captured image. At this time, the control unit 6 can obtain a captured image as shown in Fig. 5. Here, the captured image is shown to transition from black to white, for example, as the resistance value of the pixel increases, that is, the temperature increases.

[0028] Next, the control unit 6 judges whether or not the conditions are such that the light collection position P1 is moved in a direction away from the shutter 4 and the imaging unit 3 (step S4). For example, the control unit 6 judges whether or not the average value of the temperature in the second range of the captured image is equal to or higher than the second threshold value. Here, the second range is a range that the temperature of the shutter 4 may affect within the imaging area. For example, as shown in FIG. 4, when the shutter 4 covers the entire imaging unit 3, the second range is all pixels, but the second range is not limited to this. In addition, the second threshold value can be set to a temperature slightly lower than the temperature at which the shutter 4 is damaged when light L such as sunlight is incident on the shutter 4. However, the second threshold value may be set to a temperature at which damage to the shutter 4 can be suppressed. The second threshold value is calculated based on, for example, the distance from the shutter 4 to the imaging unit 3, the material of the shutter 4, the thickness of the shutter 4, the volume of the shutter 4, and the like. For example, the closer the distance from the shutter 4 to the imaging unit 3, the higher the second threshold value. For example, the lower the heat resistance temperature of the material of the shutter 4, the higher the second threshold value. For example, the thinner the shutter 4 is, the higher the second threshold value is set. Furthermore, the control unit 6 may add, in addition to the condition based on the average value of the temperature in the second range, for example, the time elapsed since execution of step S1 to the determination conditions for whether or not to move the light collection position P1 in a direction away from the shutter 4 and the image capture unit 3. For example, the condition that a certain period of time has elapsed since execution of step S1 may be added to the determination for whether or not to move the light collection position P1 in a direction away from the shutter 4 and the image capture unit 3.

[0029] When the control unit 6 determines that the conditions are not met for moving the light collection position P1 in a direction away from the shutter 4 and the imaging unit 3 (NO in step S4), the control unit 6 proceeds to the process of step S6. On the other hand, when the control unit 6 determines that the conditions are met for moving the light collection position P1 in a direction away from the shutter 4 and the imaging unit 3 (YES in step S4), the control unit 6 moves at least a part of the lens unit 2 so that the light collection position P1 moves in a direction away from the shutter 4 and the imaging unit 3 (step S5). Specifically, based on the difference between the second threshold value and the surface temperature of the shutter 4, the control unit 5 controls the drive unit 5 to move the second lens 2b to the + side of the Y axis so that the light collection position P1 of the light L moves away from the + side of the Y axis with respect to the reference light collection position P2.

[0030] In detail, the distance between the reference focusing position P2 and the focusing position P1 of light L is set in advance based on the difference between the second threshold value and the surface temperature of the shutter 4, and the distance between the reference focusing position P2 and the focusing position P1 of light L is set to become wider as the value obtained by subtracting the second threshold value from the surface temperature of the shutter 4 (a positive number greater than or equal to 0) increases.

[0031] Therefore, the control unit 6 controls the drive unit 5 so that the amount of movement of the collection position P1 of the light L toward the + side of the Y axis relative to the reference collection position P2 increases as the value obtained by subtracting the second threshold from the surface temperature of the shutter 4 increases. As a result, the second lens 2b moves toward the + side of the Y axis relative to the arrangement position of the second lens 2b where the collection position P1 of the light L is arranged at the reference collection position P2 when the imaging device 1 is in a normal state, as shown in Fig. 4.

[0032] In this way, by moving the focusing position P1 of the light L relative to the reference focusing position P2, it is possible to disperse the amount of energy when the light L is incident on the shutter 4, and to suppress damage such as peeling of the coating on the shutter 4 and deformation of the shutter 4. This is particularly effective when a thin or light material is used for the shutter 4 so that the shutter can be opened and closed quickly for mechanical shutter correction.

[0033] Moreover, since the focusing position P1 of the light L is moved to the +Y axis side, the focusing position P1 of the light L does not approach the shutter 4. Therefore, damage to the shutter 4 can be reliably suppressed.

[0034] Next, the control unit 6 judges whether or not the conditions are met for moving the light collection position P1 in a direction closer to the shutter 4 and the image capture unit 3 (step S6). For example, the control unit 6 judges whether or not the average value of the temperature in the second range in the imaging area of ​​the shutter 4 in the captured image is less than a third threshold value set in advance. Here, the third threshold value can be set to be equal to or less than the second threshold value, for example, a temperature 10°C lower than the second threshold value. In addition to the condition based on the average value of the temperature in the second range, the control unit 6 may add, for example, the elapsed time since the execution of step S5 to the judgment condition for whether or not to move the light collection position P1 in a direction closer to the shutter 4 and the image capture unit 3. For example, the condition that a certain period of time has elapsed since the execution of step S5 may be added to the judgment for moving the light collection position P1 in a direction closer to the shutter 4 and the image capture unit 3.

[0035] When the control unit 6 determines that the conditions are not met for moving the light collection position P1 in a direction approaching the shutter 4 and the imaging unit 3 (NO in step S6), the control unit 6 returns to the process of step S3. When the control unit 6 determines that the conditions are met for moving the light collection position P1 in a direction approaching the shutter 4 and the imaging unit 3 (YES in step S6), the control unit 6 moves at least a part of the lens unit 2 so that the light collection position P1 moves in a direction approaching the shutter 4 and the imaging unit 3 (step S7). Specifically, the control unit 6 controls the drive unit 5 to move the second lens 2b to the negative side of the Y axis so that the interval between the reference light collection position P2 and the light collection position P1 of the light L becomes narrower as the value obtained by subtracting the third threshold from the surface temperature of the shutter 4 becomes smaller. In other words, as the value obtained by subtracting the third threshold from the surface temperature of the shutter 4 becomes smaller, the second lens 2b approaches the arrangement position of the second lens 2b when the imaging device 1 is in a normal state. Here, if the reference focusing position P2 and the focusing position P1 of the light L are the same, that is, if the driving unit 5 has not moved the second lens 2b to the + side of the Y axis, the process of step S7 is skipped.

[0036] Next, the control unit 6 determines whether the condition for opening the shutter 4 is met (step S8). For example, the control unit 6 determines whether the average value of the temperature in the second range in the imaging area of ​​the shutter 4 in the captured image is less than a fourth threshold value set in advance. Here, the fourth threshold value can be set to be equal to or less than the third threshold value, for example, a temperature 10°C lower than the third threshold value. Furthermore, the control unit 6 may add the position of the focusing position P1 of the light L to the conditions for determining whether to open the shutter 4, in addition to the condition based on the average value of the temperature in the second range. For example, the condition that the position of the focusing position P1 of the light L has returned to the reference focusing position P2 may be added to the determination for opening the shutter 4.

[0037] When the control unit 6 determines that the condition for opening the shutter 4 is not satisfied (NO in step S8), the control unit 6 returns to the process of step S3. When the control unit 6 determines that the condition for opening the shutter 4 is satisfied (YES in step S8), the control unit 6 controls the shutter 4 to open the shutter 4 (step S9) and returns to the process of step S1. At this time, the second lens 2b is disposed at the arrangement position of the second lens 2b in the normal state of the imaging device 1, and the light collection position P1 of the light L may have returned to the reference light collection position P2, but if the light collection position P1 of the light L has not returned to the reference light collection position P2, the control unit 6 moves the second lens 2b to the arrangement position of the second lens 2b in the normal state. This causes the imaging device 1 to transition from the state in which the high-temperature object is being photographed to the normal state.

[0038] In this way, the imaging device 1 and the control method for the imaging device 1 of the present embodiment block the incidence of light L into the imaging unit 3 by the shutter 4 when the imaging device 1 is in an operating state and shooting an image of a high-temperature object. Moreover, when the imaging device 1 is in an operating state and shooting an image of a high-temperature object, the second lens 2b is moved to move the focusing position P1 of the light L away from the reference focusing position P2 on the +Y axis so that the amount of energy input to the shutter 4 is dispersed. This makes it possible to suppress damage to the imaging unit 3 and the shutter 4 when the imaging device 1 is in an operating state.

[0039] Moreover, in this embodiment, when the focusing position P1 of the light L is moved away from the reference focusing position P2, the focusing position P1 of the light L is moved toward the + side of the Y axis, so that the focusing position P1 of the light L does not approach the shutter 4. Therefore, damage to the shutter 4 can be reliably suppressed.

[0040] In addition, in this embodiment, the control unit 6 controls the drive unit 5 so that the amount of movement of the focusing position P1 of the light L relative to the reference focusing position P2 increases as the difference between the second threshold value and the derived surface temperature of the shutter 4 increases.

[0041] As a result, when moving the focusing position P1 of light L away from the reference focusing position P2, if the difference between the second threshold and the surface temperature of the shutter 4 is small, the amount of movement of the second lens 2b is smaller than when the difference between the second threshold and the surface temperature of the shutter 4 is large, so that the time spent from step S7 to step S9 can be shortened and power consumption of the imaging device 1 can be suppressed.

[0042] The configurations of the lens unit 2 and the drive unit 5 are not limited to those described above, and may be any configuration that can move the focusing position P1 of the light L incident on the imaging device 1 in the Y-axis direction. For example, the first lens 2a may move, or both the first lens 2a and the second lens 2b may move. Therefore, the shapes of the first lens 2a and the second lens 2b may be changed as appropriate. The number of lenses may also be changed as appropriate.

[0043] In the above embodiment, the second lens 2b is moved in step S7, but the second lens 2b does not have to be moved. In this case, when the average value of the temperature in the second range in the imaging area of ​​the shutter 4 in the captured image becomes less than the fourth threshold, the driving unit 5 may be controlled so that the second lens 2b is disposed at the position where the second lens 2b is disposed when the imaging device 1 is in the normal state.

[0044] In addition, in the above embodiment, when the focusing position P1 of the light L is moved away from the reference focusing position P2, the focusing position P1 of the light L is moved toward the + side of the Y axis. However, if the distance between the shutter 4 and the imaging unit 3 is wide, the focusing position P1 of the light L may be moved toward the - side of the Y axis.

[0045] The present disclosure is not limited to the present embodiment, and can be modified as appropriate without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0046] 1. Imaging device 2 lens section, 2a first lens, 2b second lens 3 imaging section, 3a light incidence surface 4. Shutter 5 Drive unit 6. Control Unit AX optical axis L light P1 Light focusing position P2 Reference focusing position of light

Claims

1. An imaging unit that captures a thermal image; a lens unit for guiding light captured by the imaging unit to the imaging unit; a drive unit that moves at least a part of the lens unit in the optical axis direction; a shutter disposed between the lens unit and the imaging unit; a control unit that controls the drive unit based on a surface temperature of the shutter derived based on an image captured by the imaging unit of the shutter in a closed state, so that a focusing position of the light moves in the optical axis direction with respect to a reference focusing position where the light is focused on a light incident surface of the imaging unit; An imaging device comprising:

2. The imaging device according to claim 1 , wherein when the focusing position is moved so that the focusing position is moved away from the reference focusing position, the control unit controls the drive unit so that the focusing position is moved in an incident direction of the light.

3. 3. The imaging device according to claim 1, wherein the control unit controls the drive unit so that an interval between the reference focusing position and the focusing position becomes wider as a value (wherein a positive number greater than or equal to 0) obtained by subtracting a preset temperature from the surface temperature becomes larger.

4. The imaging device according to claim 1 , wherein the control unit controls the shutter to be opened when the shutter is closed, based on the surface temperature.

5. a step of acquiring a captured image by causing the imaging unit to capture an image of the shutter, the shutter being disposed between the imaging unit and a lens unit for guiding light captured by the imaging unit to the imaging unit, in a closed state; a step of moving at least a part of the lens unit in an optical axis direction based on a surface temperature of the shutter derived based on the captured image, thereby moving a focusing position of the light in the optical axis direction with respect to a reference focusing position where the light is focused on a light incident surface of the image capturing unit; A control method for an imaging apparatus comprising:

Images