JP2013161011A - Imaging device - Google Patents

Abstract

Conventionally, since the amount of focus change due to IRCF insertion / extraction is performed only for a specific light source, the correction amount stored in advance when light that is not the specified light source enters is not necessarily the correct correction amount. As a result, the focus may be out of focus. An object of the present invention is to quickly correct an optimum focus position without being affected by a change in wavelength component of incident light due to insertion / extraction of an optical filter as compared with the prior art.
A lens control unit that performs focusing, a filter control unit that performs insertion / extraction of an optical filter, an exposure control unit that adjusts brightness of a captured image, and a focus movement amount associated with the insertion / extraction of the optical filter are stored. In the imaging apparatus having the correction storage unit, the focus is adjusted once when the optical filter is inserted and removed, the focus correction amount at the time of the focus adjustment is stored, and after the focus correction amount is stored, the previous focus is stored. The focus position is corrected by inserting and removing the optical filter using the correction amount.
[Selection] Figure 3

Description

  The present invention relates to an imaging apparatus, and more particularly to focus focus position correction associated with insertion and removal of an optical filter.

  Conventionally, a video signal of an image pickup apparatus forms an image on the image pickup element through light passing through a lens through an infrared cut filter (IRCF).

  The IRCF prevents infrared light that cannot be detected by the human eye from entering the image sensor, and prevents the infrared light from causing a reddish image.

  Then, the light from which the infrared component is cut is converted into a video signal through the image sensor, and the white balance (WB) adjustment is performed from the video signal, and the RGB (red, green, blue) components are balanced to obtain a color image. Output.

  On the other hand, in order to improve the sensitivity of the image sensor, the IRCF that has been conventionally cut by the IRCF is taken into the image sensor by extracting the IRCF in the previous stage of the image sensor from the optical path to improve the sensitivity. It was.

  However, since the RGB balance of the video signal is lost by removing the IRCF and it becomes difficult to obtain the WB, when the IRCF is removed, the color image output is switched to the monochrome image output. The method of photographing is used.

  In addition, since the optical path length from the lens to the image sensor changes due to the insertion / extraction of the IRCF, in order to prevent the change of the optical path length in the previous period, the dummy glass is generally inserted / extracted in accordance with the insertion / extraction of the IRCF.

  Furthermore, since the wavelength component of the light incident on the image sensor changes due to IRCF insertion / extraction, defocusing is prevented by correcting the focus position according to the incident light.

  With such a technique, it has been possible to increase the brightness of a captured image and to perform shooting without blurring with high visibility even for a low-illuminance subject.

  Conventionally, various methods have been conceived as methods of focus correction by inserting and removing optical filters.

  For example, in the past, the amount of focus change due to IRCF insertion / extraction was assumed only for a specific light source, so the correction amount stored in advance when light that was not the specified light source entered was not necessarily correct. In some cases, the amount of focus was not maintained, and as a result, the focus was still out of focus.

  Therefore, Patent Document 1 discloses a method in which a correction amount stored in advance is adjusted according to the ratio of RGB components entering the sensor, and a focus correction amount due to a difference in incident light is calculated.

  Further, Patent Document 2 discloses a technique for correcting a focus shift by adjusting an amount of focus correction due to a difference in incident light components each time by performing an AF operation in accordance with IRCF insertion / extraction.

JP-A-11-305107 JP-A-2005-242105

  However, the above-described method of Patent Document 1 has a problem in that it takes time to perform focus correction by IRCF insertion / extraction because the correction amount is determined according to the ratio of RGB color components.

  For example, when the IRCF is extracted from the IRCF insertion state, the correct RGB ratio is not known unless the RGB component ratio is measured after the IRCF is extracted. It takes a long time to adjust the focus, and the image is out of focus and difficult to see.

  Furthermore, since the correction amount differs depending on each ZOOM position, it is necessary to store the correction amount at each ZOOM position in advance, and if correction is to be made with high accuracy, the correction amount data stored in advance increases.

  In the method of Patent Document 2, since the AF operation is performed every time the IRCF is inserted / removed, the focus position of the screen changes during the AF operation, so that the image is difficult to see.

  Further, when IRCF is inserted or removed, for example, when IRCF is removed, the infrared component light that has been cut so far also enters the image sensor, and the amount of light entering the image sensor increases rapidly, so-called luminance shock. If there is a sudden change in brightness, and the focus is not focused properly and the process of returning to the proper exposure state is slow, focusing by the AF operation may not be successful and the focus may be blurred. there were.

  Accordingly, an object of the present invention is to provide a method for quickly correcting an optimum focus position without being affected by changes in the optical path length of incident light due to insertion / extraction of an optical filter and changes in the wavelength component of incident light. It provides easy-to-view images that are in focus.

  In order to achieve the above object, the present invention provides a lens control unit that performs focusing, a filter control unit that performs insertion / extraction of an optical filter, an exposure control unit that adjusts brightness of a captured image, and insertion / extraction of the optical filter. And a correction storage unit that stores the accompanying focus movement amount.When the optical filter is inserted / removed, focus is performed once, the focus correction amount when the focus is performed is stored, and the focus correction amount is calculated. After the storage, the imaging apparatus is characterized in that the focus position is corrected by inserting and removing the optical filter by using the previous focus correction amount.

  According to the present invention, it is possible to provide a method for quickly correcting an optimum focus position without being affected by a change in the optical path length of incident light and a change in the wavelength component of incident light due to insertion and removal of an optical filter. It is possible to provide an easy-to-view video that matches.

Basic camera configuration block diagram in the present invention Spectral characteristics example of sensor Flow when switching from day mode to night mode and from night mode to day mode in Example 1 Flow of processing when switching from day mode to night mode in Example 2 Flow of processing when switching from night mode to day mode in Example 2 Flow of processing when switching from day mode to night mode in Example 3 Flow of processing when switching from night mode to day mode in Example 3

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is an example of an embodiment of the present invention.

  In FIG. 1, a lens group (101) is an optical system that condenses incident light from a subject on an image sensor (104).

  Light entering the camera through the lens (101) passes through the optical filter (102), passes through the color filter (103) arranged in a predetermined order for each pixel on the light receiving surface of the image sensor (104), Light is received by the image sensor (104).

  Here, an IRCF (102-1) and a cavity (102-2) are arranged in the optical filter (102).

  The cavity (102-2) refers to a situation in which no optical filter is disposed, and a so-called dummy glass or the like that maintains the optical path length may be included.

  The IRCF (102-1) drops light having an infrared wavelength in order to prevent infrared light from entering the image sensor.

  As a result, infrared light that cannot be captured by the human eye is prevented from entering the image sensor so that the color image becomes reddish.

  FIG. 2 shows the spectral characteristics of the image sensor and the IRCF transmittance.

  For example, when the light that has passed through the lens and passed through the color filter is a primary color filter, red, green, and blue (RGB) light components are captured by the image sensor.

  The light components are captured with the sensitivity shown in FIG. 2, and at that time, the light components are taken in according to the transmittance of the IRCF shown in FIG.

  The IRCF has a lower transmittance on the long wavelength side than red, which includes a component having a long wavelength among the light components.

  This indicates that the sensitivity is reduced with respect to the red component.

  In this way, the red component is prevented from being reddish by cutting a wavelength called an infrared region that cannot be captured by the human eye.

  The imaging element (104) outputs captured image information to be captured as an analog signal.

  The picture imaged by the image sensor (104) is gain-controlled by the AGC (105) and the luminance information of the video signal is adjusted, and the analog image signal is converted into a digital signal by the AD converter (106). .

  The video signal processing unit (107) performs predetermined processing on the digital imaging signal from the A / D conversion unit (106) and outputs a luminance signal and a color signal for each pixel, and creates an output video. Each parameter for camera control is created.

  Examples of this parameter include those used for aperture control, focus control, and white balance control for adjusting color.

  The video signal output unit outputs the video signal created by the previous video signal processing unit (107) to the outside.

  The exposure adjustment unit (109) calculates luminance information in the shooting screen from the luminance information output from the video signal processing unit (107).

  When the brightness of the image is determined and determined to be dark, the filter controller (110) inserts the cavity (102-2) on the optical axis, and when it is determined to be bright, the IRCF (102-1) is determined. ) Is inserted on the optical axis.

  Here, the mode in which the IRCF is inserted is referred to as a day mode, and the state in which the IRCF is removed and a cavity is inserted is referred to as a night mode.

  The lens control unit (111) controls the lens group (101) to move the lens to a focus position based on the focus information created by the previous video signal processing unit (107).

  In general, the focus information is information obtained by performing focusing using a method such as contrast AF or phase difference AF, which is a function called autofocus (AF) that automatically performs focusing.

  The contrast AF is a method of creating a signal from the contrast of the video and focusing using the high frequency component. The phase difference AF is divided into two images from the lens, and the focus position is determined from the imaging interval. It is a method to match.

  The correction storage unit (112) stores a focus correction amount that is performed when the optical filter is inserted and removed, and uses the stored correction amount to perform focus correction associated with the optical filter insertion and removal.

  In addition, the AF evaluation values after Example 2 described later are also stored here.

  The video signal subjected to the camera control as described above is output to the outside from the video signal output unit (108).

  The feature in this case is that, in such a configuration example, the correction amount by inserting and removing the optical filter is not stored in advance, but the optimum correction amount is derived for the environment where the camera is installed, and the focus correction is performed quickly. It is.

  Therefore, at the time of inserting and removing the optical filter, the AF operation is performed at least once to focus, the focus movement amount at this time is stored, and thereafter, the stored correction amount is used to perform the focus correction.

  Specific examples of this case are shown below.

  The basic mechanism of the present invention will be described below with reference to the first embodiment of the present invention.

  FIG. 3 is an example of an embodiment of the present invention, and is a flow showing a correction operation accompanying optical filter insertion / extraction.

  First, the case of transition from the day mode to the night mode will be described.

  It is determined whether the current brightness is equal to or less than a predetermined optical filter insertion / removal brightness threshold (301). If it is determined that the brightness is equal to or less than a predetermined amount, a focus correction amount associated with the optical filter insertion / removal is determined. It is determined whether it has already been stored (302).

  If the correction amount is not yet stored, the focus position before the optical filter is extracted is stored (303), and the optical filter is extracted (304).

  Since the focus position is changed by removing the optical filter, focusing is performed by AF operation (305).

  The focus stop position at this time is stored, and the focus correction amount and the AF evaluation value after switching from the day mode to the night mode are stored from the difference from the focus position (303) when the optical filter is inserted (306).

  Thereafter, when the focus correction amount is stored, after the optical filter extraction operation (307), the AF correction operation is not performed, and the focus correction is performed using the previous focus correction amount (308).

  However, if the AF evaluation value stored in the AF evaluation value storage (306) has changed by a predetermined amount or more after performing the focus correction by removing the optical filter (309), it is determined that the focus position of the subject has changed. Focusing is performed again by AF operation (310).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the day mode to the night mode are stored (311).

  Next, a case where the night mode is changed to the day mode will be described.

  First, it is determined whether or not a predetermined brightness is obtained (312).

  If the current brightness is equal to or greater than a predetermined brightness threshold of the optical filter insertion / extraction, the optical filter is inserted into the optical path (313).

  Then, in accordance with the insertion of the optical filter, focus correction is performed using the correction amount (306) stored when switching from the day mode to the night mode (314), and the AF evaluation value after the focus correction is stored (315).

  However, if the AF evaluation value stored in the AF evaluation value storage (315) has changed by a predetermined amount or more after inserting the optical filter and performing focus correction (316), it is determined that the focus position of the subject has changed. Then, focus is performed again by AF operation (317).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the night mode to the day mode are stored (318).

  As described above, according to this embodiment, it is possible to quickly correct the focus position optimally without being affected by the change in the optical path length of the incident light and the change in the wavelength component of the incident light due to the insertion and removal of the optical filter. Is possible.

  The mechanism of the present invention will be described below with reference to the second embodiment of the present invention.

  FIG. 4 shows another example of the embodiment of the present invention and shows a transition when switching from the day mode to the night mode. FIG. 5 shows a transition when switching from the night mode to the day mode. .

  Unlike the first embodiment, the present embodiment assumes a case where the correction amount when switching from the day mode to the night mode and the correction amount when switching from the night mode to the day mode are separately provided.

  This is because of the difference in brightness when switching from day mode to night mode and when switching from night mode to day mode.For example, when sunset and sunrise, or when the surroundings are dark, the lights are turned on. This is a case where the wavelength component of light is changed such that the light is extinguished.

  First, the case of transition from the day mode to the night mode will be described.

  It is determined whether the current brightness is equal to or less than a predetermined threshold of optical filter insertion / extraction (401). If it is determined that the brightness is not more than a predetermined amount, the focus correction amount associated with the optical filter insertion / extraction has already been determined. It is determined whether it is stored (402).

  If the correction amount is not yet stored, the focus position before the optical filter is extracted is stored (303), and the optical filter is extracted (404).

  Since the focus position is changed by removing the optical filter, focusing is performed by AF operation (405).

  The focus stop position at this time is stored, and the focus correction amount and the AF evaluation value after switching from the day mode to the night mode are stored from the difference from the focus position (403) when the optical filter is inserted (406).

  Thereafter, when the focus correction amount is stored, after the optical filter extraction operation (407), focus correction is performed using the focus correction amount without performing the AF operation (408).

  However, if the AF evaluation value stored in the AF evaluation value storage (406) has changed by a predetermined amount or more after the optical filter is removed and the focus is corrected (409), it is determined that the focus position of the subject has changed. Focusing is performed again by AF operation (410).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the day mode to the night mode are stored (411).

  Next, a case where the night mode is changed to the day mode will be described.

  It is determined whether or not the current brightness is equal to or greater than a predetermined brightness threshold of the optical filter insertion / extraction (501) When it is determined that the brightness is equal to or greater than a predetermined amount, the focus correction amount associated with the optical filter insertion / extraction Is already stored (502).

  If the correction amount has not yet been stored, the focus position with the optical filter removed is stored (503), and the optical filter is inserted (504).

  Then, since the focus position changes due to the insertion of the optical filter, focusing is performed by AF operation (505).

  The focus stop position at this time is stored, and the focus correction amount is calculated from the difference from the focus position (503) when the optical filter is removed, and the AF evaluation value after switching from the night mode to the day mode is stored (506).

  After that, when the focus correction amount is stored, after the optical filter insertion operation (507), the focus correction is performed using the previous focus correction amount without performing the AF operation (508).

  However, if the AF evaluation value stored in the AF evaluation value storage (506) has changed by a predetermined amount or more after the optical filter is inserted and the focus is corrected (509), it is determined that the focus position of the subject has changed. Then, focus is performed again by the AF operation (510).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the night mode to the day mode are stored (511).

  As described above, according to the present embodiment, it is possible to quickly correct the focus position optimally without being affected by the change in the wavelength component of the incident light due to the insertion / extraction of the optical filter as compared with the conventional case.

  Next, a third embodiment of the present invention will be described.

  FIG. 6 shows another example of the embodiment of the present invention and shows a transition when switching from the day mode to the night mode.

  Unlike the second embodiment, the present embodiment assumes a case where the focus correction amount suitable for the subject and the shooting scene is calculated when the shooting area of the camera changes.

  Specifically, it is a case where the shooting scene is changed such as panning (P) for moving the camera left and right, tilting (T) for moving up and down, rotation (R) for rotation, zooming (Z) for enlarging the subject, and the like.

  This embodiment takes into consideration that the illumination light source that illuminates the subject changes due to the scene change, and the focus movement amount to be corrected also changes.

  First, the case of transition from the day mode to the night mode will be described.

  It is determined whether or not the current brightness is equal to or less than a predetermined threshold of optical filter insertion / extraction (601). It is determined whether it is stored (602).

  If the correction amount is not yet stored, the focus position before the optical filter is extracted is stored (603), and the optical filter is extracted (604).

  Since the focus position is changed by removing the optical filter, focus is performed by AF operation (605).

  The focus stop position at this time is stored, and the focus correction amount and the AF evaluation value after switching from the day mode to the night mode are stored from the difference from the focus position (603) when the optical filter is inserted (606).

  Thereafter, when the focus correction amount is stored, after the optical filter extraction operation (607), when the PTRZ operation is not performed (608), the AF operation is not performed and the previous focus correction amount is used. Correction is performed (609).

  However, if the AF evaluation value stored in the AF evaluation value storage (606) has changed by a predetermined amount or more after performing the focus correction by removing the optical filter (610), it is determined that the focus position of the subject has changed. Focusing is performed again by AF operation (611).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the day mode to the night mode are stored (612).

  If the PTRZ operation is performed even when the focus correction amount is stored (608), it is determined that the shooting scene has changed as described above, and the AF operation is performed again for focusing. (611).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the day mode to the night mode are stored (612).

  Next, the transition from the night mode to the day mode is the same as when the day mode is changed from the night mode to the night mode in Example 2 and when the night mode is changed to the day mode. Since the difference is only an addition as in the third embodiment, the description is omitted here.

  As described above, according to the present embodiment, it is possible to quickly correct the focus position optimally without being affected by the change in the wavelength component of the incident light due to the insertion / extraction of the optical filter as compared with the conventional case.

  Next, a fourth embodiment of the present invention will be described.

  FIG. 7 shows another example of the embodiment of the present invention and shows a transition when switching from the night mode to the day mode.

  Since the transition when switching from the day mode to the night mode is the same as that in FIG. 6 shown in the third embodiment, the description thereof is omitted here.

  The following describes switching from night mode to day mode.

  It is determined whether or not the current brightness is equal to or greater than a predetermined optical filter insertion / extraction brightness threshold (701). It is determined whether it is stored (702).

  If the correction amount is not yet stored, the focus position before the optical filter is inserted is stored (703), and the optical filter is inserted (704).

  Then, since the focus position is changed by inserting the optical filter, focusing is performed by AF operation (705).

  The focus stop position at this time is stored, and the focus correction amount is calculated from the difference from the focus position (703) when the optical filter is removed, and the AF evaluation value after switching from the night mode to the day mode is stored (706).

  Thereafter, when the focus correction amount is stored, after the optical filter insertion operation (707), when the PTRZ operation is not performed (708), the AF operation is not performed and the previous focus correction amount is used. Correction is performed (709).

  However, if the AF evaluation value stored in the AF evaluation value storage (706) has changed by a predetermined amount or more after inserting the optical filter and performing focus correction (710), it is determined that the focus position of the subject has changed. Then, focusing is performed again by AF operation (712).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the night mode to the day mode are stored (713).

  Further, if the PTRZ operation is performed even when the focus correction amount is stored (708), it is further determined whether a color component change has occurred (711).

  Thereafter, as described above, when the PTRZ operation is performed, since the shooting scene has changed, it is basically necessary to focus again by the AF operation. (611).

  However, if there is no change in the color component even if the scene changes, the image is shot with the same light source, so the focus correction amount may be the same as the previous PTRZ position.

  Therefore, when the color components are the same, focus correction is performed using the previously acquired focus correction amount (706) (709).

  However, if the AF evaluation value stored in the AF evaluation value storage (706) has changed by a predetermined amount or more after inserting the optical filter and performing focus correction (710), it is determined that the focus position of the subject has changed. Then, focusing is performed again by AF operation (712).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the night mode to the day mode are stored (713).

  Further, when the focus correction amount is stored, there is a PTRZ operation (708), and when a color component change occurs (711), it is determined that the subject shooting scene has changed and the AF operation is performed again to focus. (712).

  Then, the focus correction amount at that time and the AF evaluation value after switching from the night mode to the day mode are stored (713).

  As described above, according to the present embodiment, it is possible to quickly correct the focus position optimally without being affected by the change in the wavelength component of the incident light due to the insertion / extraction of the optical filter as compared with the conventional case.

  According to the present invention, it is possible to quickly correct the focus position optimally without being affected by the change in the wavelength component of the incident light caused by the insertion / extraction of the optical filter as compared with the prior art.

101: Lens group 102-1: IRCF
102-2: Cavity 103: Color filter 104: Image sensor 105: AGC
106: A / D conversion 107: Video signal processing unit 108: Video signal output unit 109: Exposure control unit 110: Filter control unit 111: Lens control unit 112: Correction storage unit

Claims (5)

A lens control unit that performs focusing, a filter control unit that inserts and removes an optical filter, an exposure control unit that adjusts the brightness of a captured image, and a correction storage unit that stores the amount of focus movement associated with the insertion and removal of the optical filter; In an imaging device having
When the optical filter is inserted / removed, focus is performed once, and the focus correction amount when the focus is performed is stored. After the focus correction amount is stored, the optical filter is inserted / removed using the previous focus correction amount. An image pickup apparatus that performs correction of a focus position according to.   The imaging apparatus according to claim 1, wherein a focus correction amount is stored in each of a case where the optical filter is removed and a case where the optical filter is inserted when the correction amount is obtained, and is adjusted according to the insertion and removal of the optical filter. An image pickup apparatus that performs focus correction using the focus correction amount.   3. The imaging apparatus according to claim 1 or 2, further comprising at least one of panning, tilting, rotation, and zooming functions, or determining that the imaging apparatus has been panned, tilted, rotated, or zoomed. In the imaging apparatus having at least one of the functions to perform focus correction again even if the correction amount associated with insertion / extraction of the optical filter is stored when the panning, tilting, rotation, or zooming is performed An image pickup apparatus that performs an operation and newly stores a focus correction amount.   The imaging apparatus according to claim 3, wherein the panning, tilting, rotation, and zooming operations are performed in an imaging apparatus that further includes a color determination unit that determines a change in a color component of a subject captured by the imaging device. However, if the color change by the color discriminating means is within a predetermined amount, the correction amount associated with the insertion / extraction of the optical filter is used as it is. 2. The focus focus alignment evaluation value stored after focus correction by insertion / extraction of the optical filter and focus focus alignment evaluation obtained again after focus correction by insertion / removal of the optical filter according to claim 1. When a change of a predetermined amount or more is found in the comparison of the evaluation value, the focus correction operation by focus is performed again, and the evaluation value for focus focus alignment at that time is stored. An imaging device.