JP2019204020A - Imaging device and control method thereof - Google Patents

Abstract

To make suitable focus control in an imaging device possible.SOLUTION: An imaging device includes: an imaging optical system; focus means for adjusting an image forming position of the imaging optical system; imaging means for converting a subject image formed by the imaging optical system into an electric signal; filter means for controlling a wavelength area of light entering the imaging means; and luminance acquisition means for acquiring a luminance value of the subject image from the electric signal acquired by the imaging means. The filter means is configured to be able to switch at least three wavelength characteristics different from each other. The focus means adjusts the image forming position of the imaging optical system on the basis of at least three luminance values acquired for the at least three respective wavelength characteristics.SELECTED DRAWING: Figure 6

Description

  The present invention relates to focus control in an imaging apparatus.

  The human eye is sensitive to light having a wavelength from 380 nm to 780 nm, which is called the visible range, but has a characteristic that the sensitivity differs for each wavelength. And it has little sensitivity to light having a wavelength longer than 700 nm. On the other hand, an image sensor such as a CMOS sensor has sensitivity in a wide wavelength region including an infrared region (near infrared region). Therefore, in order to match the color reproducibility of the imaging apparatus with human color vision characteristics, an infrared light removal filter (IRCF) may be provided in front of the imaging element. The IRCF is a visibility correction filter that passes light in the visible light region but does not pass light in the infrared region.

  By the way, when photographing under low illuminance such as at night when the subject brightness is low, a technique of removing IRCF from the optical path and increasing sensitivity is often used. However, in a general photographic lens, the imaging position changes according to the wavelength of light (referred to as axial chromatic aberration). Therefore, when the IRCF is put in the optical path, the image in the visible light region is focused, and when the IRCF is removed from this state, the image in the infrared region is out of focus.

  Therefore, in Patent Document 1, the luminance is acquired by the imaging device in two states, a state where a filter is inserted in the optical path and a state where the filter is removed. A technique for correcting focus position adjustment based on a difference in luminance obtained in two states is disclosed.

JP 2014-225828 A

  By the way, in a general photographic lens, the change in the imaging position depending on the change in the wavelength in the infrared region is larger than the change in the imaging position depending on the change in the wavelength in the visible light region. However, in the technique disclosed in Patent Document 1, the luminance of visible light and the luminance of infrared light can be compared, but it is possible to determine which wavelength of light in the infrared region is included. Absent. For this reason, when a plurality of infrared illuminations having different wavelengths are used as the external illumination, appropriate focus control may not be performed. On the other hand, if an attempt is made to create a photographic lens with reduced axial chromatic aberration over a wide wavelength region including the infrared region, problems such as enlarging the photographic lens and an increase in manufacturing cost arise.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a technique that enables suitable focus control in an imaging apparatus.

In order to solve the above-described problems, an imaging apparatus according to the present invention has the following configuration. That is, the imaging device
An imaging optical system;
Focusing means for adjusting the imaging position of the imaging optical system;
Imaging means for converting a subject image formed by the imaging optical system into an electrical signal;
Filter means for controlling the wavelength region of light incident on the imaging means;
Luminance acquisition means for acquiring the luminance value of the subject image from the electrical signal obtained by the imaging means;
Have
The filter means is configured to be able to switch at least three wavelength characteristics different from each other,
The focus unit adjusts the imaging position of the imaging optical system based on at least three luminance values acquired by the luminance acquisition unit for each of the at least three wavelength characteristics by the filter unit.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which enables suitable focus control in an imaging device can be provided.

It is a block diagram which shows the structure of the imaging device which concerns on 1st Embodiment. It is a figure explaining the example of arrangement | positioning relationship between a filter holder and an image pick-up element. It is a figure which shows the relationship between the wavelength of light, and a focus position. It is a figure which shows the spectral characteristic of infrared illumination. 5 is a flowchart of focus control in the first embodiment. It is a flowchart of focus control in a 2nd embodiment. It is a flowchart of focus control in a 3rd embodiment. It is a figure explaining other examples of arrangement relation of each filter and an image sensor.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiments are merely examples, and are not intended to limit the scope of the present invention.

(First embodiment)
As a first embodiment of an image pickup apparatus according to the present invention, an image pickup apparatus having a day mode using IRCF and a night mode not using IRCF as shooting modes will be described below as an example.

<Day mode and night mode>
A general image sensor has sensitivity to a wavelength range wider than the wavelength range of visible light. For this reason, a technique is adopted in which the IRCF is removed from the optical path under low illuminance where the subject brightness is lowered, and the sensitivity is increased by allowing light in the infrared region to pass through.

  For example, an infrared / visible camera or the like that switches between two modes: a day mode in which IRCF is inserted into the optical path during the day and a night mode in which IRCF is removed from the optical path during the night. An imaging device is used. Note that if the light in the infrared region is allowed to pass, the color balance is lost, so that a black-and-white image may be taken in the night mode. As a mode switching method, there is a case where a function called automatic day / night (ADN) which automatically switches between the day mode and the night mode is used. For example, switching is performed based on the shutter speed, aperture value, AGC (automatic gain adjustment), screen brightness, and the like of the camera.

  In addition, external illumination may be used when a subject to be photographed has low illuminance such as at night. Then, there is an increasing demand for photographing in night mode using infrared illumination using infrared light, which is light having a wavelength invisible to human eyes. However, in a general photographic lens, the imaging position changes depending on the wavelength of light, and the change is large in the infrared region. Therefore, when photographing in night mode using infrared illumination, the focus may be blurred depending on the wavelength of light in the infrared illumination. Therefore, it is desired to perform focus control by determining which wavelength of light is included in the infrared region.

<Device configuration>
FIG. 1 is a block diagram illustrating a configuration of the imaging apparatus according to the first embodiment. The imaging device includes a part of a lens barrel 16 that includes an imaging optical system and an imaging element and outputs a video signal, and a part that controls each part of the lens barrel 16.

  Specifically, the lens barrel 16 includes a zoom lens 1, a focus lens 2, a filter holder 3, an image sensor 4, an image sensor control circuit 9, a video signal processing circuit 10, and a video signal output circuit 11. Here, the filter holder 3 holds an infrared light removal filter (IRCF) 31, a dummy glass 32, and a band pass filter 33. The lens barrel 16 includes a zoom drive motor 5 that drives the zoom lens 1, a focus drive motor 6 that drives the focus lens 2, and a filter (F) drive motor 7 that drives the filter holder 3. The lens barrel 16 is connected to a pan / tilt (PT) drive motor 8 in order to change the shooting direction.

  In addition, a pan / tilt drive motor driver 12, a filter drive motor driver 13, a focus motor driver 14, and a zoom motor driver 15 that control the operation of each motor described above are arranged as parts for controlling the respective parts of the lens barrel 16. Further, a luminance value calculation circuit 17, a camera control circuit 18, a memory 19, and an operation switch 20 are arranged.

  The zoom drive motor 5 moves the zoom lens 2 in the optical axis direction based on a control signal from the zoom motor driver 15. The focus drive motor 6 moves the focus lens 2 in the optical axis direction based on a control signal from the focus motor driver 14. The filter drive motor 7 moves the filter holder 3 based on the control signal of the filter drive motor driver 13 to switch the IRCF 31, the dummy glass 32, and the band pass filter 33 in the optical path. Details will be described later with reference to FIG. The pan / tilt drive motor 8 changes the shooting direction by controlling the pan and tilt directions of the lens barrel 16 based on the control signal of the pan / tilt drive motor driver 12.

  The camera control circuit 18 outputs control signals to the zoom motor driver 15, the focus motor driver 14, the filter drive motor driver 13, and the pan / tilt drive motor driver 12. The camera control circuit 18 controls luminance calculation by the luminance calculation circuit 17.

  The memory 19 stores various information related to various controls. For example, the current pan / tilt position of the lens barrel 16, the position of the filter holder 3, the position of the zoom lens 1, and the position of the focus lens 2 are stored in the memory 19 through the camera control circuit 18 based on the control state of each motor. . Further, a focus correction amount (difference from the focus position in visible light) according to the wavelength is stored in the memory 19. The focus correction amount will be described later with reference to FIG. Further, the memory 19 stores one or more shooting conditions for shooting as preset setting values. The preset setting value includes the shooting direction (pan / tilt position), zoom magnification (zoom position), and focus position for each shooting target.

  The operation switch 20 is a switch that receives operations and settings related to the imaging apparatus from the user. For example, changes in zoom, focus, shooting mode, and pan / tilt can be accepted. It also accepts settings for the preset patrol function.

  Note that the preset patrol function is a function for patroling and shooting a plurality of shooting targets. For example, the traveling setting can be managed by setting each photographing target by the preset setting value described above and setting information such as the photographing order and the staying time together. Pan / tilt, zoom, and focus are driven according to the patrol setting, and shooting is performed while patroling the shooting target. By repeating the preset tour based on the tour settings at a predetermined interval, the user can periodically acquire a plurality of images to be captured using one camera.

  In the preset tour, the manual focus (MF) mode is generally set. The MF mode is a mode in which only focus control based on the focus position included in the preset setting value is performed, and adaptive focus tracking is not performed according to a change in the subject. However, it is also possible to set an autofocus (AF) mode that performs adaptive focus follow-up according to changes in the subject.

  The image sensor 4 converts an incident subject image into an electrical signal, and the analog signal is converted into a digital signal by an A / D converter in the image sensor control circuit 9. Thereafter, after various signal processing is performed by the video signal processing circuit 10, it is output from the video signal output circuit 11 as a color or monochrome video signal. The luminance calculation circuit 17 calculates the luminance value of the subject image based on the video signal output from the video signal processing circuit 10.

  The camera control circuit 18 has a shooting mode determination function for determining whether to perform shooting in the day mode or the night mode. Further, the camera control circuit 18 moves the filter holder 3 to hold and compare the luminance values obtained by the luminance value calculation circuit 17 when each of the IRCF 31, the dummy glass 32, and the band pass filter 33 is disposed in the optical path. It has a function. Details will be described later with reference to FIGS.

  FIG. 2 is a diagram for explaining an example of the arrangement relationship between the filter holder and the image sensor. Specifically, a state in which the imaging surfaces of the filter holder 3 and the imaging element 4 are observed from the front along the optical axis is shown. In FIG. 2, the range of pixels used for imaging in the image sensor 4 is shown as a photographic pixel range 4a, and the range of pixels used for luminance acquisition described later is shown as a luminance acquisition range 4b. The intersection 34 between the imaging pixel range 4a and the optical axis is at the center of the imaging pixel range 4a.

  Three openings are arranged in the filter holder 3, and the IRCF 31, the dummy glass 32, and the band pass filter 33 are attached on substantially the same plane. The filter holder 3 is linearly moved by the filter drive motor 7 in a direction substantially along the optical axis (along 35 shown in FIG. 2). Note that a disk-shaped filter holder 3 having three openings on the circumference may be used. In that case, the filter holder 3 is rotated by the filter drive motor 7, whereby the IRCF 31, the dummy glass 32, and the band pass filter 33 are switched.

  Here, it is assumed that the imaging element 4 has sensitivity to light with a wavelength of 380 nm to 1000 nm. The IRCF 31 has a characteristic of transmitting light with a wavelength of 380 nm to 700 nm. The dummy glass 32 has a characteristic of transmitting light having a wavelength of 380 nm to 2500 nm. The band pass filter 33 has a characteristic of transmitting light having a wavelength of 700 nm to 900 nm. That is, the band-pass filter 33 is configured to transmit only a part of the wavelength region of the near-infrared wavelength region that the dummy glass 32 transmits.

  FIG. 2A shows the position of the filter holder 3 in the day mode, in which the IRCF 31 is in the optical path. In the day mode state shown in FIG. 2A, the luminance acquisition range 4b is covered with the IRCF 31, and light having a wavelength of 380 nm to 700 nm can enter the luminance acquisition range 4b.

  FIG. 2B shows the position of the filter holder 3 in the night mode, in which the dummy glass 32 is in the optical path. In the night mode state shown in FIG. 2B, the luminance acquisition range 4b is covered with the dummy glass 32, and light having a wavelength of 380 nm to 2500 nm can enter the luminance acquisition range 4b. However, the luminance with respect to light having a wavelength of 380 nm to 1000 nm is calculated according to the sensitivity characteristics of the image sensor.

  FIG. 2C shows the position of the filter holder 3 in the middle of switching between the day mode and the night mode. As illustrated, the luminance acquisition range 4b is covered with the bandpass filter 33, and light having a wavelength of 700 nm to 900 nm can enter the luminance acquisition range 4b.

  By moving the filter holder 3 by the filter drive motor 7, it is possible to continuously switch the above three luminance acquisition states. Note that the IRCF 31, the dummy glass 32, and the bandpass filter 33 have substantially the same thickness and refractive index so that the optical path length does not change even when the IRCF 31, the dummy glass 32, and the band pass filter 33 are switched.

  FIG. 3 is a diagram illustrating the relationship between the wavelength of light and the focus position. Note that the focus position is the position of the focus lens at which the captured image is focused on the image sensor. As shown in the figure, the focus position changes depending on the wavelength. In particular, in the infrared region of 700 nm or more, the amount of change in the focus position increases as the wavelength increases. This is due to the axial chromatic aberration of the taking lens.

  As described above, only light having a wavelength in the range of 380 nm to 700 nm is obtained in the day mode, but light having a wavelength in the range of 380 nm to 2500 nm can be incident on the imaging element 4 in the night mode. Since the sensitivity of the imaging device 4 is in the range of 380 nm to 1000 nm, the imaging device 4 performs imaging with light having a wavelength in the range of 380 nm to 700 nm in the day mode and in the range of 380 nm to 1000 nm in the night mode. . Therefore, in the night mode, there is a possibility that the focus position at which an appropriate focus is obtained differs depending on the wavelength included in the captured image. Therefore, a focus correction amount corresponding to the wavelength is stored in the memory 19 in advance.

  FIG. 4 is a diagram illustrating spectral characteristics of infrared illumination. 4A shows the first illumination having a peak in the vicinity of 800 nm, and FIG. 4B shows the second illumination having a peak in the vicinity of 950 nm.

  In the day mode when the IRCF 31 enters the optical path, the wavelength of 700 nm or more is cut. Therefore, even if the subject is illuminated with the first illumination or the second illumination, this wavelength component is not received by the image sensor, and there is almost no luminance of these wavelength components. On the other hand, in the night mode in which the dummy glass 32 enters the optical path, when the subject is illuminated with the first illumination or the second illumination, these wavelength components are received by the image sensor, and the luminance of these wavelength components is high. Become. Therefore, under IR illumination, the brightness value when IRCF 31 is entered and when dummy glass 32 is entered will change significantly. Therefore, if the rate of change is large, infrared component light will enter. Judgment can be made.

  However, whether the IRCF 31 and the dummy glass 32 are illuminated by the first illumination having a peak near 800 nm or the second illumination having a peak near 950 nm only from changes in luminance values when the IRCF 31 and the dummy glass 32 are put in the optical path. I can't judge. Therefore, in the first embodiment, the wavelength component included in the captured image is determined in more detail by further adding the luminance value when the bandpass filter 33 is put in the optical path to the determination.

  When the subject is illuminated by the first illumination and the bandpass filter 33 enters the optical path, the wavelength component of the first illumination enters the image sensor and is received. On the other hand, when the subject is illuminated by the second illumination and the band-pass filter 33 enters the optical path, the wavelength component of the second illumination does not enter the image sensor. Therefore, whether the first illumination or the second illumination is illuminated if the change in the luminance value when the band-pass filter 33 enters the optical path and the change in the luminance value when the dummy glass 32 enters the optical path are seen. Can be identified.

  Therefore, when the day mode is switched to the night mode, the brightness values when the IRCF 31, the band pass filter 33, and the dummy glass 32 are in the optical path are compared. This makes it possible to determine which wavelength component contains more light in the captured image. As a result, it is possible to perform shooting with less focus deviation by correcting the focus position corresponding to the wavelength component that is included more.

<Operation of the device>
FIG. 5 is a flowchart of focus control in the first embodiment. Here, a description will be given of a mode in which the luminance value is acquired and the focus position is corrected using the switching from the day mode to the night mode as a trigger.

  In S101, the camera control circuit 18 determines whether a switching signal from the day mode to the night mode is input. If it is determined that it has been input, the process proceeds to S102. In S102, the camera control circuit 18 determines whether the focus is set to the auto focus (AF) mode or the manual focus (MF) mode. If it is the MF mode, the process proceeds to S103, and if it is the AF mode, the process is terminated. That is, in the AF mode, focus control is adaptively performed based on the received image.

  In S103, the camera control circuit 18 reads the luminance value Y1 in the day mode (that is, the state in which the IRCF 31 is inserted in the optical path), and in S104, the camera control circuit 18 reads the focus position. In S105, the camera control circuit 18 starts driving the filter holder 3 in a direction substantially perpendicular to the optical axis by driving the filter driving motor in accordance with the filter driving signal.

  In S <b> 106, the camera control circuit 18 reads the luminance value Y <b> 3 when the bandpass filter 33 is in the optical path. That is, while driving the filter holder 3, the luminance value Y <b> 3 is acquired at a timing when the bandpass filter 33 attached to the filter holder 3 passes through the luminance acquisition range 4 b of the image sensor 4. In S107, the camera control circuit 18 reads the luminance value Y2 when the dummy glass 32 is in the optical path. That is, after the drive of the filter holder 3 is completed, the luminance value Y2 is acquired in a state where the dummy glass 32 attached to the filter holder 3 covers the luminance acquisition range 4b of the image sensor 4.

  By driving without stopping from the state in which the IRCF 31 is inserted into the optical path to the state in which the dummy glass 32 is inserted into the optical path, it is possible to shorten the time required to acquire the three luminance values. Further, the relationship between the size of the movement direction 35 of the band-pass filter 33, the driving speed for switching the filter holder 3, and the luminance acquisition time is such that the transit time is a value obtained by dividing the driving speed by the size of the moving direction 35. It is better to set it to be shorter than the acquisition time. By setting in this way, the size of the band-pass filter 33 can be reduced while enabling the luminance acquisition in a state where the band-pass filter 33 in the middle of switching is in the luminance acquisition range 4b.

  In S108, the camera control circuit 18 compares the luminance value Y1 with the value obtained by subtracting the luminance value Y1 from the luminance value Y2. For example, it is determined whether or not a value obtained by subtracting the luminance value Y1 from the luminance value Y2 by the luminance value Y1 is greater than a predetermined value T1. If it is less than or equal to the predetermined value T1, it is determined that there is little infrared light, and the process proceeds to S109. On the other hand, if it is larger than the predetermined value T1, it is determined that there is much infrared light, and the process proceeds to S110. In S109, the camera control circuit 18 determines that there is no focus correction because there is little infrared light, and the process ends.

  That is, the luminance value Y1 is luminance with light having a wavelength in the range of 380 nm to 700 nm, and the luminance value Y2 is luminance with light having a wavelength in the range of 380 nm to 1000 nm. Therefore, the value obtained by subtracting the luminance value Y1 from the luminance value Y2 is the luminance of light of 700 nm to 1000 nm. That is, the ratio of the luminance between light of 380 nm to 700 nm and light of 700 nm to 1000 nm is compared with the predetermined value T1. This is because when this ratio is small, it can be determined that there is little infrared light (700 nm to 1000 nm) and the influence on the focus is small.

  In addition, when the sensitivity for each wavelength in the imaging device 4 is not constant (for example, the sensitivity to the wavelength of 900 nm is lower than the sensitivity to the wavelength of 600 nm), the above-described predetermined value is taken into consideration in consideration of the sensitivity of the imaging device 4 for each wavelength. A value T1 may be set.

  In S110, the camera control circuit 18 determines whether or not a value obtained by dividing the luminance value Y2 by subtracting the luminance value Y1 and the luminance value Y3 by the luminance value Y3 is greater than a predetermined value T2. If it is larger than the predetermined value T2, the process proceeds to S111, and if it is less than the predetermined value T2, the process proceeds to S112.

  Here, the luminance value Y1 is the luminance with light having a wavelength in the range of 380 nm to 700 nm, and the luminance value Y2 is the luminance with light having a wavelength in the range of 380 nm to 1000 nm. The luminance value Y3 is the luminance of light having a wavelength in the range of 700 nm to 900 nm. Therefore, the value obtained by subtracting the luminance value Y1 and the luminance value Y3 from the luminance value Y2 is the luminance of light of 900 nm to 1000 nm. That is, the ratio of the luminance of light of 700 nm to 900 nm and the luminance of light of 900 nm to 1000 nm is compared with the predetermined value T2. When this ratio is small, it can be judged that there is much light of 700 nm to 900 nm, and when this ratio is large, it is judged that there is much light of 900 nm to 1000 nm.

  In S111, the camera control circuit 18 determines that the focus position needs to be corrected to a focus position corresponding to a wavelength of 950 nm. “950 nm” is set as a representative value within the range of 900 nm to 1000 nm. In S113, the camera control circuit 18 performs the focus drive to the focus position corresponding to the wavelength of 950 nm and ends. Specifically, the focus lens 2 is moved by a correction amount corresponding to 950 nm. The correction amount is a difference from the focus position in visible light obtained with reference to FIG.

  In S112, the camera control circuit 18 determines that the focus position needs to be corrected to a focus position corresponding to a wavelength of 800 nm. “800 nm” is set as a representative value within a range of 700 nm to 900 nm. In S114, the camera control circuit 18 performs focus drive to the focus position corresponding to the wavelength of 800 nm and ends. Specifically, the focus lens 2 is moved by a correction amount corresponding to 800 nm. The correction amount is a difference from the focus position in visible light obtained with reference to FIG.

  As described above, according to the first embodiment, the luminance value is obtained when three types of filters having different wavelength characteristics are placed in the optical path. And the wavelength component contained more in a captured image was determined based on the obtained three luminance values. Thereby, more suitable focus control can be performed.

  Further, by arranging the band pass filter 33 between the IRCF 31 and the dummy glass 32 in the filter holder 3, three luminance values can be obtained continuously when switching from the day mode to the night mode. Moreover, it becomes possible to suppress the enlargement of the filter holder 3.

(Second Embodiment)
In the second embodiment, a description will be given of a mode in which, in an imaging device that performs preset patrol, a luminance acquisition operation is performed to switch a shooting target, a wavelength component of light is determined, and focus control is performed. Since the apparatus configuration (FIGS. 1 and 2) is the same as that of the first embodiment, description thereof is omitted.

  When the imaging target is switched by the preset tour, pan / tilt driving and / or zoom driving are performed, and there is a possibility that the wavelength component included in the captured image changes. Therefore, even when the wavelength component included in the captured image changes, it is possible to perform in-focus shooting.

<Operation of the device>
FIG. 6 is a flowchart of focus control in the second embodiment. As described above, here, a description will be given of a mode in which luminance value acquisition and focus position correction are performed using preset position switching in a preset tour as a trigger.

  In S201, the camera control circuit 18 determines whether or not a signal for movement to the next preset position is input. If it is determined that it has been input, the process proceeds to S202. In S202, the camera control circuit 18 drives the pan / tilt drive motor 8, the zoom motor 5, and the focus motor 6 according to the preset setting values. That is, driving is performed based on the shooting direction (pan / tilt position), zoom magnification (zoom position), and focus position included in the preset setting value, and the camera moves to the next preset position.

  In S203, the camera control circuit 18 determines whether the focus is set to the auto focus (AF) mode or the manual focus (MF) mode. If it is MF mode, the process proceeds to S204, and if it is AF mode, the process is terminated.

  In S204, the camera control circuit 18 determines whether or not the shooting state is in the night mode. If it is not the night mode, the process ends. If it is the night mode, the process proceeds to S205. That is, when the mode is not the night mode, the shooting is performed in the day mode (that is, the state in which the IRCF 31 is inserted in the optical path), and there is no need for focus correction.

  In S205, the camera control circuit 18 reads the current focus position. In S206, the camera control circuit 18 reads the luminance value Y2 in the night mode (that is, the state where the IRCF 31 is not inserted in the optical path). In S207, the camera control circuit 18 starts driving the filter holder 3 in a direction substantially perpendicular to the optical axis by driving the filter driving motor in accordance with the filter driving signal.

  In S208, the camera control circuit 18 reads the luminance value Y3 in a state where the bandpass filter 33 is in the optical path. That is, while driving the filter holder 3, the luminance value Y <b> 3 is acquired at a timing when the bandpass filter 33 attached to the filter holder 3 passes through the luminance acquisition range 4 b of the image sensor 4. In S209, the camera control circuit 18 reads the luminance value Y1 when the IRCF 31 is in the optical path. That is, after the drive of the filter holder 3 is completed, the luminance value Y1 is acquired in a state where the IRCF 31 attached to the filter holder 3 covers the luminance acquisition range 4b of the image sensor 4.

  In S210, the camera control circuit 18 drives the filter holder 3 in the direction opposite to S207 with respect to the optical axis by driving the filter driving motor in accordance with the filter driving signal. And it returns to the state (namely, night mode) in which the dummy glass 32 attached to the filter holder 3 covered the brightness | luminance acquisition range 4b of the image pick-up element 4. FIG.

  In S211, the camera control circuit 18 determines whether or not a value obtained by dividing the luminance value Y2 by subtracting the luminance value Y1 and the luminance value Y3 by the luminance value Y3 is greater than a predetermined value T2. If it is larger than the predetermined value T2, the process proceeds to S212, and if it is equal to or smaller than the predetermined value T2, the process proceeds to S213.

  In S212, the camera control circuit 18 determines that the focus position corresponding to the wavelength of 950 nm is appropriate. In S214, the camera control circuit 18 determines whether or not the focus position read in S205 is a position corresponding to a wavelength of 950 nm. If it is a corresponding position, the process is terminated without correcting the focus position. If it is not the corresponding position, in S215, the camera control circuit 18 performs the focus drive to the focus position corresponding to the wavelength of 950 nm and ends.

  In S213, the camera control circuit 18 determines that the focus position corresponding to the wavelength of 800 nm is appropriate. In S216, the camera control circuit 18 determines whether or not the focus position read in S205 is a position corresponding to a wavelength of 800 nm. If it is a corresponding position, the process is terminated without correcting the focus position. If not, the camera control circuit 18 performs focus drive to the focus position corresponding to the wavelength of 800 nm and ends in S217.

  As described above, according to the second embodiment, the wavelength component is determined and focus control is performed when the imaging target is switched. This makes it possible to perform more suitable focus control even when the shooting position or range changes due to pan / tilt or zoom and the illumination state changes.

  In the above description, the process of determining “shooting in the night mode without infrared illumination” (S108 to S109) is omitted because it is a repetition of the description of the first embodiment. However, you may comprise so that the said process (S108-S109) may be performed between S210 and S211.

(Third embodiment)
In the third embodiment, a description will be given of a mode in which, in an imaging apparatus that takes an image of the same subject for a long time, a luminance acquisition operation is performed based on a timer to determine a wavelength component of light and focus control is performed. Since the apparatus configuration (FIGS. 1 and 2) is the same as that of the first embodiment, description thereof is omitted.

  When photographing the same subject for a long time, there is a possibility that wavelength components included in a photographed image may change due to environmental changes such as ambient lighting. Therefore, even when the wavelength component included in the captured image changes, it is possible to perform in-focus shooting.

<Operation of the device>
FIG. 7 is a flowchart of focus control in the third embodiment. As described above, here, a mode in which a luminance value is acquired and a focus position is corrected using a timer as a trigger will be described. As the timer, a preset time, a predetermined time interval, and the like are set.

  In S301, the camera control circuit 18 determines whether a luminance acquisition signal is input. Note that the luminance acquisition signal is generated and input when a luminance acquisition time preset by the timer has arrived.

  In S302, the camera control circuit 18 determines whether the focus is set to the auto focus (AF) mode or the manual focus (MF) mode. If it is the MF mode, the process proceeds to S303, and if it is the AF mode, the process is terminated.

  In S303, the camera control circuit 18 determines whether or not the shooting state is in the night mode. If it is not the night mode, the process ends. If it is the night mode, the process proceeds to S304. That is, when the mode is not the night mode, the shooting is performed in the day mode (that is, the state in which the IRCF 31 is inserted in the optical path), and there is no need for focus correction.

  In S304, the camera control circuit 18 reads the current focus position. In S305, the camera control circuit 18 reads the luminance value Y2 in the night mode (that is, the state where the IRCF 31 is not inserted in the optical path). In S306, the camera control circuit 18 starts driving the filter holder 3 in a direction substantially perpendicular to the optical axis by driving the filter driving motor in accordance with the filter driving signal.

  In S307, the camera control circuit 18 reads the luminance value Y3 in a state where the bandpass filter 33 is in the optical path. That is, while driving the filter holder 3, the luminance value Y <b> 3 is acquired at a timing when the bandpass filter 33 attached to the filter holder 3 passes through the luminance acquisition range 4 b of the image sensor 4. In S308, the camera control circuit 18 reads the luminance value Y1 when the IRCF 31 is in the optical path. That is, after the drive of the filter holder 3 is completed, the luminance value Y1 is acquired in a state where the IRCF 31 attached to the filter holder 3 covers the luminance acquisition range 4b of the image sensor 4.

  In S309, the camera control circuit 18 drives the filter holder 3 in the direction opposite to S306 with respect to the optical axis by driving the filter driving motor in accordance with the filter driving signal. And it returns to the state (namely, night mode) in which the dummy glass 32 attached to the filter holder 3 covered the brightness | luminance acquisition range 4b of the image pick-up element 4. FIG.

  In S310, the camera control circuit 18 determines whether or not a value obtained by dividing the luminance value Y2 by subtracting the luminance value Y1 and the luminance value Y3 by the luminance value Y3 is greater than a predetermined value T2. If it is larger than the predetermined value T2, the process proceeds to S311. If it is equal to or smaller than the predetermined value T2, the process proceeds to S312.

  In S311, the camera control circuit 18 determines that the focus position corresponding to the wavelength of 950 nm is appropriate. In S313, the camera control circuit 18 determines whether or not the focus position read in S304 is a position corresponding to a wavelength of 950 nm. If it is a corresponding position, the process is terminated without correcting the focus position. If not, the camera control circuit 18 performs focus drive to the focus position corresponding to the wavelength of 950 nm and ends in S314.

  In S312, the camera control circuit 18 determines that the focus position corresponding to the wavelength of 800 nm is appropriate. In S315, the camera control circuit 18 determines whether or not the focus position read in S304 is a position corresponding to a wavelength of 800 nm. If it is a corresponding position, the process is terminated without correcting the focus position. If not, the camera control circuit 18 performs focus drive to the focus position corresponding to the wavelength of 800 nm and ends in S316.

  As described above, according to the third embodiment, the wavelength component is determined using the timer as a trigger to perform focus control. This makes it possible to perform more suitable focus control even when a change in the environment such as ambient lighting occurs when shooting the same shooting target for a long time.

(Modification)
In the first to third embodiments described above, the configuration in which the luminance is acquired in the luminance acquisition range 4b (FIG. 2) located in the center of the image sensor has been described. This is based on the assumption that the subject to be focused is located at the center of the shooting screen and the lighting state of the subject is determined. However, another luminance acquisition range 4b may be set.

  FIG. 8 is a diagram illustrating another example of the arrangement relationship between each filter and the image sensor. In FIG. 8, the size of the luminance acquisition range 4 b in the moving direction is set larger than the width of the bandpass filter 33. When the filter holder 3 is driven from the bottom to the top with respect to the luminance acquisition range 4b, a transition is made as shown in FIG. 8 (a) → FIG. 8 (b) → FIG. 8 (c). The sum of luminance values in the luminance acquisition range 4b sequentially acquired during this transition may be used as the luminance value.

  In the above description, an example in which 800 nm and 950 nm are assumed as infrared light wavelengths of external illumination and a bandpass filter of 700 nm to 900 nm is used has been described. That is, the fact that 800 nm infrared illumination is used is estimated based on the luminance value in the wavelength range of 700 nm to 900 nm, and the fact that 950 nm infrared illumination is used is indicated in the luminance value in the wavelength range of 900 nm to 1000 nm. It was set as the structure estimated based on. However, the above-described wavelength value is merely an example, and for example, a band-pass filter having other characteristics can be used depending on the assumed wavelength of external illumination.

  In the above description, the dummy glass is provided in the optical path in the night mode, but a plain configuration may be used. Furthermore, although only one bandpass filter is provided, by providing a plurality of bandpass filters having different wavelength characteristics, it is possible to determine the range of wavelengths included in the captured image in more detail and to improve the focusing performance. Become.

(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  DESCRIPTION OF SYMBOLS 1 Zoom lens; 2 Focus lens; 3 Filter holder; 4 Imaging element; 5 Zoom drive motor; 6 Focus drive motor; 7 Filter drive motor; 8 Pan tilt drive motor; 9 Image sensor control circuit; 10 Video signal processing circuit; 12 pan / tilt drive motor driver; 13 filter drive motor driver; 14 focus motor driver; 15 zoom motor driver; 16 lens barrel; 17 luminance value calculation circuit; 18 camera control circuit; 19 memory; 20 operation switch; IRCF; 32 dummy glass; 33 Band-pass filter

Claims (10)

An imaging optical system;
Focusing means for adjusting the imaging position of the imaging optical system;
Imaging means for converting a subject image formed by the imaging optical system into an electrical signal;
Filter means for controlling the wavelength region of light incident on the imaging means;
Luminance acquisition means for acquiring the luminance value of the subject image from the electrical signal obtained by the imaging means;
Have
The filter means is configured to be able to switch at least three wavelength characteristics different from each other,
The focus unit adjusts an imaging position of the imaging optical system based on at least three luminance values acquired by the luminance acquisition unit for each of the at least three wavelength characteristics by the filter unit. An imaging device. The focusing means identifies at least two infrared illuminations having different wavelengths in the near-infrared wavelength region based on the at least three luminance values, and performs the imaging based on the identified wavelengths of the infrared illumination. The imaging apparatus according to claim 1, wherein an imaging position of the optical system is adjusted. The at least three wavelength characteristics are:
A first wavelength characteristic that transmits a visible light wavelength region and does not transmit a near-infrared wavelength region;
A second wavelength characteristic that transmits visible and near-infrared wavelength regions;
A third wavelength characteristic that transmits only a partial wavelength region of the near infrared;
The imaging apparatus according to claim 2, comprising: The filter means includes
A filter holder in which a first filter having the first wavelength characteristic, a second filter having the second wavelength characteristic, and a third filter having the third wavelength characteristic are arranged on substantially the same plane;
Drive means for moving the filter holder so that any one of the first filter, the second filter, and the third filter is inserted into the optical path of the imaging optical system;
Have
The imaging apparatus according to claim 3, wherein the third filter is disposed between the first filter and the second filter. The luminance acquisition unit inserts the first luminance value and the third filter obtained when the first filter is inserted into the optical path of the imaging optical system while the driving unit is moving the filter holder. The imaging apparatus according to claim 4, wherein the brightness value is continuously acquired in the order of the third brightness value obtained when the second brightness value is obtained and the second brightness value obtained when the second filter is inserted. The focusing means is configured to generate the at least two infrared rays based on a ratio value between a luminance value obtained by subtracting the first luminance value and the third luminance value from the second luminance value and the third luminance value. The imaging apparatus according to claim 5, wherein illumination is identified. The imaging apparatus according to claim 1, wherein the luminance acquisition unit acquires the at least three luminance values when the filter unit switches wavelength characteristics. The imaging device has a function to circulate and shoot a plurality of shooting targets,
The luminance acquisition unit controls the filter unit to acquire the at least three luminance values when switching an imaging target by the function. Imaging device. The imaging device has a timer,
The luminance acquisition means controls the filter means to acquire the at least three luminance values when a preset time in the timer arrives. The imaging device according to item. A method for controlling an imaging apparatus,
The imaging device
An imaging optical system;
Focusing means for adjusting the imaging position of the imaging optical system;
Imaging means for converting a subject image formed by the imaging optical system into an electrical signal;
Filter means for controlling the wavelength region of light incident on the imaging means;
Luminance acquisition means for acquiring the luminance value of the subject image from the electrical signal obtained by the imaging means;
Have
The control method is:
A switching step in which the filter means switches at least three wavelength characteristics different from each other;
The luminance acquisition means acquires at least three luminance values for the at least three wavelength characteristics; and
An adjustment step in which the focusing means adjusts an imaging position of the imaging optical system based on the at least three luminance values;
A method for controlling an imaging apparatus, comprising:

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