JP2017062281A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device that enables an optimal bracket shooting to be taken for each shooting scene when taking an automatic bracket shooting with a polarization filter.SOLUTION: An imaging device comprises: an imaging unit that shoots a subject; a polarization filter that is rotatably provided forward the imaging unit; rotation means that causes the polarization filter to automatically rotate in a direction around an optical axis; and bracket shooting means that, when a shooting instruction is given, automatically sets the polarization filter at a plurality of rotation angles, and takes the shooting. The imaging device is configured to: prior to the bracket shooting, take a plurality of images in advance as rotating the polarization filter by a unit rotation angle; divide the plurality of taken images into a block; specify the rotation angle in which a polarization elimination effect of each block is maximum; and on the basis of a distribution of the specified rotation angle, determine an angle at which the bracket shooting is taken.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus provided with a polarizing filter, and to a control method and program thereof.

  In photographing with a digital camera or the like, there is a method in which unnecessary reflected light as a polarization component is removed using a polarizing filter (PL filter). For example, it is known that colors such as the blueness of the sky are vividly captured when a polarizing filter is used when photographing a landscape. If a polarizing filter is used when photographing a subject in a show window, reflected light is removed and the subject is clearly captured.

  The polarizing filter can change the polarization direction of the light component to be removed by rotating the polarizing filter. In general, the polarizing filter is mounted on the front surface of the camera lens, and is adjusted to an effective angle by which the user can remove a desired light component while manually rotating the polarizing filter. On the other hand, there is a technique in which a polarizing filter is built in the camera, and the camera automatically searches for an effective angle and performs shooting.

  In Japanese Patent Laid-Open No. 2004-228688, a technique that controls the rotation of a polarizing filter installed on the optical path in front of the image sensor and makes it possible to adjust the polarizing filter to a rotation angle at which the luminance signal of the captured image data is minimized. Is disclosed.

Japanese Unexamined Patent Publication No. 2006-208714

  There is a method called a PL bracket that captures multiple images while the camera automatically swings the rotation angle of the polarization filter built into the camera. At the time of PL bracket shooting, there are cases where the rotation angle of the polarizing filter is shaken at a preset angle such as 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees to perform bracket shooting. In this case, for example, a desired effect cannot be obtained in a scene where the polarization removal effect is the largest at 60 degrees when viewed on the entire screen.

  There is also a method of searching for the PL bracket image by searching for an angle having the greatest depolarization effect on the entire screen and swinging the angle around the angle with a constant width. However, the effect of depolarization is not uniform for the screen depending on the scene, and may differ for each region of the screen. For example, in the scene as shown in FIG. 3, even if the area A occupying the largest area on the right side of the screen is 80 degrees and the polarization removal effect is the maximum, the same is true for the area B on the upper side of the screen and the area C on the left side of the screen. The depolarization effect is not always maximized at 80 degrees. In the B region and the C region, the polarization removal effect is maximized at 30 degrees and 150 degrees, respectively.

  In that case, even if bracket shooting is performed with a fixed width (0, 40, 80, 120, 160) around the angle (80 degrees) where the depolarization effect is the largest on the entire screen, the depolarization effect is obtained for the B and C regions. It will not be possible to shoot at the maximum angle.

  An object of the present invention is to perform optimum bracket shooting for each shooting scene when performing PL bracket shooting in which a camera automatically swings the rotation angle of a polarization filter built in the camera and captures a plurality of images. It is an object of the present invention to provide an imaging apparatus that enables the above.

In order to achieve the above object, an imaging apparatus according to the present invention includes:
An imaging unit for imaging a subject;
A polarizing filter rotatably provided in front of the imaging unit;
A rotating means for automatically rotating the polarizing filter around the optical axis;
Bracket imaging means for automatically setting the polarizing filter at a plurality of rotation angles when shooting instructions are issued,
Before the bracket shooting, a plurality of images are pre-shot while rotating the polarizing filter by a predetermined unit rotation angle,
Divide multiple captured images into blocks, identify the rotation angle that has the greatest depolarization effect for each block,
The bracket shooting angle is determined based on the specified rotation angle distribution.

  According to the imaging apparatus of the present invention, when performing PL bracket shooting in which a camera automatically shoots a plurality of images while rotating the rotation angle of a polarization filter built in the camera, an optimum bracket for each shooting scene Shooting can be performed.

It is the figure which showed schematic structure of the imaging device of this invention. It is a flowchart showing the processing operation of embodiment of this invention. It is the figure which showed the example of the imaging | photography scene of this invention. It is a figure showing the change of the luminance value accompanying rotation of a polarizing filter. It is the figure which showed the histogram of the rotation angle when the luminance value for every block becomes the minimum. It is the figure which showed the example of the imaging | photography scene when implementing PL bracket imaging | photography. It is the figure which showed the histogram of a rotation angle when the luminance value for every block becomes the minimum in a certain scene. It is the figure which showed the mode when the image for evaluation of a certain scene was divided into blocks.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an imaging apparatus 100 according to an embodiment of the present invention.

  101 is a lens optical system, 102 is a mechanical shutter (illustrated as a mechanical shutter), 103 is an image sensor, 104 is a CDS circuit that performs analog signal processing, and 105 is an A / D that converts an analog signal into a digital signal. A converter 106 is a timing signal generating circuit that generates signals for operating the CDS circuit 104 and the A / D converter 105, and 107 is a driving circuit for the lens optical system 101, the mechanical shutter 102, the image sensor 103, and the polarization filter 115. , 108 is a signal processing circuit for performing signal processing necessary for image data, and 109 is an image memory for storing the image data subjected to signal processing.

  110 is an image recording medium removable from the imaging device, 111 is a recording circuit that records signal processed image data on the image recording medium 110, and 112 is an image display device that displays signal processed image data, 113. The display circuit 114 displays an image on the image display device 112, and the system control unit 114 controls the entire imaging device. In the lens optical system 101, the polarization filter 115 is installed in a state where the rotation can be controlled, and the rotation is controlled by the drive circuit 107.

Hereinafter, a photographing operation using the imaging apparatus 100 configured as described above will be described.
First, the lens optical system 101 drives the optical system according to a control signal from the system control unit 114 to form a subject image set to an appropriate brightness on the image sensor 103. The polarization filter 115 installed in the lens optical system 101 is rotationally controlled in a direction orthogonal to the optical axis of the lens optical system 101 by a control signal from the system control unit 114.

  Next, the mechanical shutter 102 is driven by a control signal from the system control unit 114 so as to shield the image sensor 103 in accordance with the operation of the image sensor 103 so that a necessary exposure time is obtained. At this time, when the image sensor 103 has an electronic shutter function, it may be used together with the mechanical shutter 102 to secure a necessary exposure time. The image sensor 103 is driven by a drive pulse based on the operation pulse generated by the timing signal generation circuit 106 controlled by the system control unit 114, and converts the subject image into an electrical signal by photoelectric conversion as an analog image signal. Output.

  The analog image signal output from the image sensor 103 is subjected to an operation pulse generated by the timing signal generation circuit 106 controlled by the system control unit 114, and the clock synchronization noise is removed by the CDS circuit 104. In 105, it is converted into a digital image signal. Next, the signal processing circuit 108 performs image processing such as color conversion, white balance, and gamma correction, resolution conversion processing, and image compression processing. The signal processing circuit 108 may output the digital image signal as it is as image data to the image memory 109 or the recording circuit 111 without performing signal processing by the control signal from the system control unit 114.

  Further, the signal processing circuit 108, when requested by the system control unit 114, information of digital image signals and image data generated in the signal processing process, for example, the spatial frequency of the image, the average value of the designated area, the compression Information such as the amount of image data or information extracted from the information is output to the system control unit 114. Further, the recording circuit outputs information such as the type and free capacity of the image recording medium 110 to the system control unit 114 when requested by the system control unit 114.

  Further, a reproduction operation when image data is recorded on the image recording medium 110 will be described. In response to a control signal from the system control unit 114, the recording circuit reads image data from the image recording medium 110. Similarly, in response to a control signal from the system control unit 114, the signal processing circuit 108 determines that the image data is a compressed image. Then, image expansion processing is performed and stored in the image memory 109. The image data stored in the image memory 109 is subjected to resolution conversion processing by the signal processing circuit 108, converted to a signal suitable for the image display device 112 by the display circuit 113, and displayed on the image display device 112. .

Next, PL bracket shooting control will be described with reference to the flowchart shown in FIG.
The control process of PL bracket shooting is executed according to a computer program stored in a memory (not shown) in the system control unit 114. FIG. 2 is a flowchart showing the flow of the PL bracket photographing process. When the imaging apparatus 100 is turned on and the imaging process is started, the process starting from step S201 is started.

  First, in step S201, when the PL bracket shooting mode is set by the user, the process proceeds to step S202. Next, in step S202, when the signal SW1 transmitted when the shutter switch is half-pressed is detected, the process proceeds to step S203. In step S203, the rotation angle θ of the polarizing filter is set to 0 ° which is the reference position.

  In step S204, the evaluation image is taken in a state where the rotation angle θ of the polarizing filter is set to 0 degree, and the process proceeds to step S205. Unlike the actual captured image that is recorded on the recording medium by PL bracketing when the shutter switch is fully pressed, this evaluation image is captured in advance while rotating the polarization filter in advance. FIG. 5 is an image acquired to determine the rotation angle of the polarizing filter during PL bracket shooting. In step S205, the rotation angle θ of the polarizing filter is set to (θ + 1) degrees, which is rotated by 1 degree from the rotation angle θ captured last time.

  In step S206, an evaluation image is taken with the rotation angle of the polarizing filter set in step S205. In step S207, it is determined whether the current rotation angle θ of the polarizing filter is greater than 180 degrees. If larger than 180 degrees, the process proceeds to step S208. On the other hand, when the angle is smaller than 180 degrees, the process returns to step S205, and the evaluation image is photographed by setting the rotation angle θ of the polarizing filter to (θ + 1) degrees that is rotated by 1 degree from the rotation angle θ photographed last time. Repeat the process.

  In step S208, as described above, a plurality of evaluation images taken while rotating the polarizing filter by 1 degree from 0 degrees to 180 degrees are divided into a plurality of blocks. FIG. 8 is a diagram showing a state when an evaluation image of a certain scene is divided into blocks. In this way, the evaluation image is divided into blocks, an average value of luminance values of all pixels included in each block is calculated, and set as a luminance value for each block.

  In step S209, the rotation angle of the polarization filter on which the evaluation image having the minimum luminance value is captured for each block is specified. FIG. 4 is a diagram showing the luminance value for each rotation angle of the polarizing filter for a block having an evaluation image divided into blocks. According to FIG. 4, it can be seen that this block has the lowest luminance at 80 degrees and the highest luminance at 170 degrees. Therefore, the rotation angle of the polarizing filter that minimizes the luminance value in this block is specified as 80 degrees.

  Further, in step S210, a histogram representing the rotation angle distribution of the polarization filter in which the evaluation image having the minimum luminance value is captured for each block specified in step S209 is created.

  In step S211, a bracket angle in PL bracket shooting is determined based on the histogram created in step S210. FIG. 5 is a diagram showing an example of the histogram created in step S210. In FIG. 5, the histogram takes a large value at the angles of A, B, and C. For this reason, in this scene, it can be seen that the scene is composed mainly of subjects that have a large depolarization effect at three types of angles A, B, and C, and these three types of angles are determined as bracket angles in PL bracket shooting. .

  Thereafter, in step S212, when the signal SW2 transmitted when the shutter switch is fully pressed is confirmed, the process proceeds to step S213.

  Finally, in step S213, PL bracket shooting is performed at the bracket angle determined in step S211, an image is recorded on the image recording medium 110, and the process ends. If you rotate the polarizing filter at this time, the brightness value of the subject will change, or the reflected light will be removed and the contrast of the subject will change.Therefore, set the exposure and focus before shooting at each rotation angle in the PL bracket. It is desirable to fix it. Here, the effect of the present invention will be described with reference to FIGS. FIG. 6 is a diagram showing an example of a shooting scene when performing PL bracket shooting.

  As described in the process of the flowchart of FIG. 2 described above, an evaluation image is taken while rotating the polarizing filter from 0 degrees to 180 degrees, the taken evaluation image is divided into blocks, and the minimum luminance in each block is obtained. It is assumed that a histogram representing the value distribution is created as shown in FIG. In the histogram of FIG. 7, among the angles from 0 degrees to 180 degrees, 80 degrees has the highest distribution as the angle at which the block having the minimum luminance exists, and then the distribution increases in the order of 150 degrees and 30 degrees. Yes. In this case, the rotation angle of the polarizing filter in PL bracket shooting is set to 30 degrees, 80 degrees, and 150 degrees, and PL bracket shooting is performed at this rotation angle in the main shooting after pressing SW2.

  FIGS. 6 (a), 6 (b), and 6 (c) show areas when grouping blocks having rotation angles of 30 degrees, 80 degrees, and 150 degrees that take the minimum luminance value in the shooting scene of FIG. FIG.

  The shooting scene of FIG. 6 is mainly composed of three areas, area A (sea), area B (sky), and area C (land). As shown in FIG. As shown in FIG. 6B, the region B takes a minimum luminance value at a rotation angle of 30 degrees, and as shown in FIG. 6C, the region C takes a rotation angle of 150 degrees. As described above, in this scene, PL bracket shooting is performed with the rotation angle of the polarization filter being 30 degrees, 80 degrees, and 150 degrees based on the histogram, so the area A that mainly constitutes the shooting scene of FIG. (Sea), Region B (Sky), Region C (Land) Each of the three regions will be photographed at the rotation angle of the polarizing filter that has the greatest polarization removal effect, making it the optimal PL bracket for the scene Shooting can be performed.

  In this embodiment, when the evaluation image is taken, the image is taken while changing the rotation angle of the polarizing filter from 0 degree to 180 degrees in increments of 1 degree. When it is desired to reduce the number of evaluation images taken as much as possible, the evaluation images may be taken in increments of 10 degrees, for example. Further, in order to perform more detailed angle setting, for example, an evaluation image may be taken in increments of 0.5 degrees.

  Further, in this embodiment, when determining the rotation angle having the greatest polarization removal effect, the rotation angle is determined based on the luminance value of the evaluation image, but may be determined based on the saturation of the evaluation image. I do not care. In that case, the saturation tends to increase due to the polarization removal, and therefore, the rotation angle at which the saturation is maximized is obtained for each block.

  Furthermore, in the present embodiment, three types of rotation angles in PL bracket shooting are selected from the histogram, but it is of course possible to use other angles. For example, when there are four types of angles with a generally high distribution in the histogram, the number of PL brackets to be photographed may be set to four. Further, for example, if the user has set the number of PL brackets to be photographed in advance as 5, the PL bracket photographing may be performed by setting the rotation angles up to the fifth highest in the histogram.

  As described above, the configuration and operation in the above-described embodiment can be appropriately changed. Software for realizing the functions of the above-described embodiments for an apparatus or a computer in the system connected to the various devices so that the various devices are operated so as to realize the functions of the above-described embodiments. The program implemented by supplying the program code and operating the various devices according to the program stored in the computer (CPU or MPU) of the system or apparatus is also included in the scope of the present invention.

  In this case, the program code of the software itself realizes the functions of the above-described embodiments, and the program code itself and means for supplying the program code to the computer, for example, the program code is stored. The storage medium constitutes the present invention. As a storage medium for storing the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) or other application software in which the program code is running on the computer, etc. It goes without saying that the program code is also included in the embodiment of the present invention even when the functions of the above-described embodiment are realized jointly.

  Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU provided in the function expansion board or function expansion unit based on the instruction of the program code Needless to say, the present invention includes a case where the functions of the above-described embodiment are realized by performing part or all of the actual processing.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

101 lens optical system, 107 drive circuit, 108 signal processing circuit, 114 system control unit,
115 Polarizing filter

Claims (6)

An imaging unit for imaging a subject;
A polarizing filter rotatably provided in front of the imaging unit;
A rotating means for automatically rotating the polarizing filter around the optical axis;
A bracket photographing means for automatically photographing the polarizing filter at a plurality of rotation angles when a photographing instruction is issued;
Before the bracket shooting, a plurality of images are pre-shot while rotating the polarizing filter by a predetermined unit rotation angle,
Divide multiple captured images into blocks, identify the rotation angle that has the greatest depolarization effect for each block,
An imaging device that determines an angle for bracket shooting based on a specified distribution of rotation angles. The imaging apparatus according to claim 1, wherein the rotation angle having the largest polarization removal effect is a rotation angle when the luminance level of each block is minimized. The imaging apparatus according to claim 1, wherein the rotation angle having the largest polarization removal effect is a rotation angle when the saturation level of each block is maximized. The imaging apparatus according to claim 1, wherein the rotation angle distribution is a histogram of rotation angles when the luminance level of each block is minimized. 5. The imaging apparatus according to claim 1, wherein the rotation angle distribution is a histogram of rotation angles when the saturation level of each block is maximized. 6. The imaging apparatus according to any one of claims 1 to 5, wherein the bracket shooting angle is an angle obtained by extracting a set number of shootings in descending order of frequency of rotation of the histogram.