JP2016126046A - Focal point detecting device and focal point detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focal point detecting device and a focal point detecting method that are capable of accurately calculating a focusing position even if a plurality of point light source subjects differing in distance exist.SOLUTION: The focal point detecting device comprises: a saturation determination part 7 for determining whether or not an imaging signal is saturated; a saturation pixel region setting part 81 for setting saturation pixel regions in which imaging signals determined to be saturated by the saturation determination part 7 exist; an attribute detection region setting part 82 for setting attribute detection regions inside the saturation pixel regions; a focal point detection region setting part 83 for classifying imaging signals included in the attribute detection regions according to attribute information, and setting a plurality of focal point detection regions including the saturation pixel regions on the basis of the positions of the imaging signals having the same attribute information; an extraction part 84 for extracting a predetermined signal component from imaging signals obtained in each of the plurality of focal point detection regions; and a focal point detection part 85 for detecting a focal point on the basis of the extracted signal component.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a focus detection apparatus and a focus detection method.

  A contrast AF method is used as one method for automatic focus detection of a photographing lens provided in an imaging apparatus. The contrast AF method is a method of calculating a focus evaluation value indicating a contrast value of a subject image formed by the photographing lens and controlling the position of the photographing lens so that the focus evaluation value becomes a peak value.

  In the contrast AF method, if there is a high-luminance subject such as a point light source in the focus detection area, the imaging signal related to the high-luminance subject may be saturated and the focus position of the photographing lens may not be detected correctly. Therefore, for example, the focus detection apparatus proposed in Patent Document 1 has a first evaluation value that is an integrated value of the imaging signal that has passed through the bandpass filter and a second evaluation that is an integrated value of the imaging signal that has not passed through the bandpass filter. The position of the photographing lens is controlled using a third evaluation value that is a difference between the maximum difference value and each difference.

JP 2007-171807 A

  In Patent Document 1, a plurality of focus detection areas determined to have saturated image pickup signals are combined into one merged area. In this case, when there are subjects with different distances in the plurality of focus detection areas determined to be saturated with the imaging signal, the focusing accuracy decreases. This decrease in focusing accuracy becomes significant when there are a plurality of point light source subjects with different distances. By combining the focus detection areas, the focus evaluation value for the point light source subject is generated in one focus detection area, and therefore an evaluation value that is not suitable depending on the degree of brightness (brightness) may be generated. There is also.

  The present invention has been made in view of the above circumstances, and a focus detection apparatus and focus detection capable of calculating a focus position with high accuracy even when a plurality of point light source subjects having different distances exist. It aims to provide a method.

  In order to achieve the above object, a focus detection apparatus according to a first aspect of the present invention is a focus detection apparatus that calculates a focus position based on an imaging signal of an imaging element that captures a subject image. A saturation determination unit that determines whether or not the image is saturated; a saturation pixel region setting unit that sets a saturation pixel region in which an imaging signal determined to be saturated by the saturation determination unit is present; and the saturation pixel An attribute detection area setting unit that sets an attribute detection area inside the area, and the imaging signals included in the attribute detection area are classified according to attribute information, and based on the position of the imaging signal having the same attribute information A focus detection region setting unit that sets a plurality of focus detection regions including the saturated pixel region; an extraction unit that extracts a predetermined signal component from the imaging signal obtained in each of the plurality of focus detection regions; Based on the issued signal component characterized by comprising the focus detection unit that performs focus detection.

  In order to achieve the above object, a focus detection method according to a second aspect of the present invention is a focus detection method for calculating a focus position based on an imaging signal of an imaging element that captures a subject image. Determining whether or not it is saturated, setting a saturated pixel area where the imaging signal determined to be saturated exists, and setting an attribute detection area within the saturated pixel area And classifying the imaging signals included in the attribute detection area according to attribute information, and setting a plurality of focus detection areas including the saturated pixel area based on the position of the imaging signal having the same attribute information And extracting a predetermined signal component from the imaging signal obtained in each of the plurality of focus detection areas, and performing focus detection based on the extracted signal component. To.

  According to the present invention, it is possible to provide a focus detection apparatus and a focus detection method capable of calculating a focus position with high accuracy even when a plurality of point light source subjects having different distances exist.

It is a block diagram of the camera provided with the focus detection apparatus which concerns on one Embodiment of this invention. It is a flowchart of AF control. It is a flowchart shown about a point light source focus detection area setting process. It is a figure shown about a point light source focus detection area. It is a figure which shows the focus evaluation value when not classifying a point light source focus detection area. It is a figure which shows the focus evaluation value at the time of classifying a point light source focus detection area. It is a flowchart shown about the modification of a point light source focus detection area setting process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a camera provided with a focus detection apparatus according to an embodiment of the present invention. The camera shown in FIG. 1 includes a photographic lens 1, a lens control unit 2, an imaging device 3, an imaging control unit 4, an imaging signal processing unit 5, an AE processing unit 6, a saturation determination unit 7, and an AF process. A unit 8, an image processing unit 9, a memory 10, a display unit 11, an operation unit 12, and a CPU 13 are included.

  The photographing lens 1 is an optical system for forming an image of a light beam from a subject on the image sensor 3. The photographing lens 1 has a focus lens. The focus lens adjusts the focal position of the photographing lens 1 by moving in the optical axis direction. The lens control unit 2 drives the focus lens of the photographing lens 1 in accordance with, for example, an instruction from the AF processing unit 8.

  The image sensor 3 is disposed on the optical axis of the photographing lens 1. The image sensor 3 has pixels. The pixels are two-dimensionally arranged and generate charges corresponding to the subject image formed by the photographing lens 1. This charge is read as an imaging signal. The imaging control unit 4 performs control of charge accumulation of the imaging device 3 and control of reading of the imaging signal according to a control signal from the CPU 13.

  The imaging signal processing unit 5 performs processing on the imaging signal read from each pixel of the imaging element 3. This processing includes processing such as analog noise removal and amplification for the imaging signal. In addition, this processing includes processing for converting an imaging signal that is an analog signal into imaging data that is a digital signal.

  The AE processing unit 6 calculates a luminance value, which is one of the attribute information of the imaging signal, for each predetermined luminance detection area based on the imaging data. Then, the AE processing unit 6 performs automatic exposure (AE) control based on the luminance value. The exposure amount of the image sensor 3 is controlled by the automatic exposure control.

  The saturation determination unit 7 determines the presence / absence of a saturated pixel. A saturated pixel is a pixel having a pixel value that has reached a predetermined saturation level. The saturation level is a predetermined level that can be regarded as a point light source, and is set to a level that is somewhat lower than the maximum value of the dynamic range of the A / D conversion of the imaging signal processing unit 5, for example.

  The AF processing unit 8 performs automatic focus (AF) control based on the imaging data in the focus detection area. At least one focus detection area is set in the entire area or a part of the imaging data. Each focus detection area is formed by one pixel or a plurality of pixels. The AF processing unit 8 includes a saturated pixel region setting unit 81, an attribute detection region setting unit 82, a focus detection region setting unit 83, an extraction unit 84, and a focus detection unit 85. The saturated pixel region setting unit 81 sets a saturated pixel region including a focus detection region including pixels in which imaging data determined to be saturated by the saturation determination unit 7 exists. The attribute detection area setting unit 82 sets an attribute detection area inside the saturated pixel area. The attribute detection area is a luminance detection area in the saturated pixel area. The focus detection area setting unit 83 sets a focus detection area in the imaging data. Further, the focus detection area setting unit 83 sets a point light source focus detection area based on the luminance value which is attribute information acquired for the attribute detection area. The point light source focus detection region is a focus detection region considered to include a point light source. The extraction unit 84 extracts the high-frequency signal component of the imaging data for each focus detection area. The high frequency signal component is extracted by, for example, a digital high pass filter. The focus detection unit 85 calculates a focus evaluation value by accumulating the image data of the extracted signal components, and performs focus control of the focus lens based on the focus evaluation value.

  The image processing unit 9 processes the imaging data to generate display image data or recording image data. This process includes processes such as white balance correction, gradation correction, and color correction. Further, the processing for recording image data includes compression processing. Further, when reproducing the image data for recording recorded in the memory 10, the image processing unit 9 performs expansion processing.

  The memory 10 includes an electrically rewritable non-volatile memory configured to be detachable from the camera body or built in the camera body. In the memory 10, image data for recording obtained by the processing of the image processing unit 9 is recorded.

  The display unit 11 displays various images such as a live view image based on the display image data generated by the processing of the image processing unit 9. The display unit 11 displays an image based on the reproduction image data obtained by the expansion processing of the image processing unit 9.

  The operation unit 12 includes an operation member for the user to operate the camera. The operation members are, for example, a power switch, a release button, a playback button, and a menu button. The operation unit 12 detects the operation state of these operation members and outputs a signal corresponding to the detected operation state.

  The CPU 13 controls processing of each block of the camera. For example, the CPU 13 performs processing according to the operation state of each operation member of the operation unit 12.

  Next, the operation of the focus detection apparatus according to this embodiment will be described. FIG. 2 is a flowchart of AF control in the present embodiment. The AF control is mainly controlled by the AF processing unit 8. Note that the AF control described below is contrast-type AF control.

  In step S101, the CPU 13 performs preprocessing such as exposure setting for AF control. The exposure setting is performed using a predetermined setting, for example. Further, the exposure setting may be performed by measuring the brightness of the imaging data.

  In step S102, the CPU 13 instructs the AF processing unit 8 to execute AF control. Upon receiving this instruction, the AF processing unit 8 sets a focus detection area. As the focus detection area, for example, an area selected by the user from a plurality of focus detection area settings is used. The setting of the focus detection area is, for example, a setting that uses one focus detection area in the screen selected by the user for focus detection, a setting that uses a plurality of focus detection areas in the screen selected by the user for focus detection, and a screen. There is a setting in which the entire area is used for focus detection.

  In step S103, the AF processing unit 8 performs a point light source focus detection area setting process. The point light source focus detection area setting process is a process for setting a focus detection area that is considered to include a point light source in the screen, in addition to the normal focus detection area. Details will be described later.

  In step S <b> 104, the AF processing unit 8 sends a lens driving instruction to the lens control unit 2. In response to this instruction, the lens control unit 2 drives the focus lens by a predetermined amount. This lens drive is a drive for detecting the peak of the focus evaluation value and is called a scan drive or the like.

  In step S105, the AF processing unit 8 obtains a focus evaluation value for each focus detection region by obtaining an integrated value of high-frequency signal components of the imaging data for each focus detection region including the point light source focus detection region.

  In step S106, the AF processing unit 8 corrects the focus evaluation value. The correction of the focus evaluation value is a correction calculation for the focus evaluation value of the point light source focus detection area. As this correction calculation, for example, a technique described in Japanese Patent Application Laid-Open No. 2011-175119 can be used.

  In step S107, the AF processing unit 8 performs a direction determination process to determine the direction in which the focus evaluation value peak exists. As a determination method, for example, the current focus evaluation value is compared with the focus evaluation value one or more times before, and if the focus evaluation value increases, the current lens driving direction is the peak of the focus evaluation value. If the focus evaluation value decreases, a method of determining that the reverse direction of the current lens driving direction is the direction in which the peak of the focus evaluation value exists can be used. When it is determined that the reverse direction of the current lens driving direction is the direction in which the peak of the focus evaluation value exists, the AF processing unit 8 instructs the lens control unit 2 to drive the focus lens in the reverse direction. Send a lens drive instruction.

  In step S108, the AF processing unit 8 determines whether or not the direction determination process is completed. This determination is performed by determining whether or not the amount of increase or decrease in the focus evaluation value is greater than or equal to a predetermined value. If it is determined in step S108 that the increase or decrease amount of the focus evaluation value is less than a predetermined value, it is determined that the direction determination process has not been completed. In this case, the process returns to step S105. That is, the processing from step S105 to step S108 is repeated until the direction determination processing is completed.

  If it is determined in step S108 that the increase or decrease amount of the focus evaluation value is greater than or equal to a predetermined value, it is determined that the direction determination process has been completed. In this case, the process proceeds to step S109. In step S109, the AF processing unit 8 performs peak detection processing. The peak detection process is a process for detecting the peak of the focus evaluation value. The peak detection process is a process for detecting a change from an increase in focus evaluation value to a decrease.

  In step S110, the AF processing unit 8 determines whether or not the peak detection process has been completed, that is, whether or not a change from an increase in focus evaluation value to a decrease has been detected. If it is determined in step S110 that the peak detection process has not been completed, the process returns to step S105. That is, the processes from step S105 to step S110 are repeated until the peak detection process is completed.

  If it is determined in step S110 that the peak detection process has been completed, the process proceeds to step S111. In step S111, the AF processing unit 8 sends a lens driving instruction to the lens control unit 2 so as to drive the focus lens to the peak position that is the position of the focus lens at which the focus evaluation value reaches a peak. Thereafter, the process of FIG. 2 ends. Note that the true peak of the focus evaluation value is obtained by interpolation between the lens position before the focus evaluation value exceeds the peak and the lens position after the peak.

  Next, the point light source focus detection area setting process will be described. FIG. 3 is a flowchart showing the point light source focus detection region setting process.

  In step S <b> 201, the AF processing unit 8 determines whether there is a saturated pixel in the imaging data using the determination result of the saturation determination unit 7. If it is determined in step S201 that there are no saturated pixels, the processing in FIG. 3 ends.

  If it is determined in step S201 that there is a saturated pixel, the process proceeds to step S202. In step S202, the AF processing unit 8 sets a saturated pixel region. The saturated pixel area is a focus detection area group composed of focus detection areas including all saturated pixels.

  In step S <b> 203, the AF processing unit 8 sets an attribute detection region inside the saturated pixel region, and acquires a luminance value for each attribute detection region from the AE processing unit 6.

  In step S204, the AF processing unit 8 determines whether or not the luminance value of a certain attribute detection region is equal to or higher than a predetermined first luminance level. The first luminance level is not limited to a predetermined level, and may be a level calculated based on an average value of all luminance detection areas.

  If it is determined in step S204 that the luminance value of the attribute detection area is equal to or higher than the first luminance level, the process proceeds to step S205. In step S205, the AF processing unit 8 sets that the luminance value of the corresponding attribute detection area belongs to the first luminance level.

  If it is determined in step S204 that the luminance value of the attribute detection area is not equal to or higher than the first luminance level, the process proceeds to step S206. In step S206, the AF processing unit 8 sets that the luminance value of the corresponding attribute detection area belongs to the second luminance level.

  In step S207, the AF processing unit 8 determines whether or not the determination of the luminance values for all the attribute detection areas in the saturated pixel area has been completed. If it is determined in step S207 that determination of luminance values for all attribute detection areas in the saturated pixel area has not been completed, the process returns to step S204. In this case, the same determination is performed for another attribute detection region in the saturated pixel region.

  If it is determined in step S207 that determination of luminance values for all attribute detection areas in the saturated pixel area has been completed, the process proceeds to step S208. In step S208, the AF processing unit 8 determines the distribution of luminance values. That is, the AF processing unit 8 determines a plurality of adjacent attribute detection areas having a luminance value of the first luminance level as the first luminance area, and determines a plurality of adjacent attribute detection areas having the luminance value of the second luminance level. The second luminance area is determined.

  In step S209, the AF processing unit 8 sets a point light source focus detection region for each luminance region. Thereafter, the process of FIG. 3 ends. In setting the point light source focus detection region, the AF processing unit 8 sets the point light source focus detection region A in the first luminance region and sets the point light source focus detection region B in the second luminance region. Here, the point light source focus detection region A is a focus detection region in the first luminance region, and does not overlap with the focus detection region in the other first luminance region and the focus detection region in the second luminance region. Is set. Similarly, the point light source focus detection region B is a focus detection region in the second luminance region, and does not overlap with the focus detection region in the other second luminance region and the focus detection region in the first luminance region. Is set.

  As described above, in the present embodiment, when there are regions around saturated pixels having different luminance levels in the screen, the region including the saturated pixels having individual luminance levels is the point light source focus detection region. Set to For example, when the point light source subject T having the first luminance level and the point light source subject S having the second luminance level are present at a longer distance than the point light source subject T as in the example of FIG. In addition to the focus detection areas M1 to M9, the point light source focus detection area B (consisting of the focus detection areas M1 and M4) corresponding to the point light source subject S and the point light source focus detection area A (focus) corresponding to the point light source subject T Detection areas M5, M6, M8, and M9).

  Here, if the point light source focus detection area A and the point light source focus detection area B are set as one point light source focus detection area, the focus evaluation value shows peaks on both the infinite side and the near side as shown in FIG. . This causes erroneous distance measurement and a decrease in distance measurement accuracy.

On the other hand, in the present embodiment, as shown in FIG. 6, since the focus evaluation value shows a peak at the focus lens position corresponding to each distance, the target object can be accurately focused. Furthermore, since it is difficult to be influenced by different high-brightness subjects and the degree of focus evaluation value correction calculation can be adjusted according to the luminance, it is possible to perform AF control with higher accuracy.
In this embodiment, the saturated pixel area is a focus detection area group composed of focus detection areas including all saturated pixels, but a set of individual saturated pixels (or a set of small areas including saturated pixels) is used. A saturated pixel region may be used. In this case, instead of providing the attribute detection area inside the saturated pixel area, the attribute detection area may be provided by combining areas around the saturated pixel area. At this time, the attribute detection area does not include the saturated pixel area, and the luminance area is set with a luminance component excluding the saturated pixel area.

[Modification]
Hereinafter, modifications of the present embodiment will be described. In the above example, the luminance value is used as the attribute information in the point light source focus detection region setting, but a value related to the color of the imaging signal may be used. The value relating to the color is, for example, a chromaticity value.

  FIG. 7 is a flowchart showing a point light source focus detection region setting process when a chromaticity value is used as attribute information. Hereinafter, differences from FIG. 3 will be described.

  The processing from step S301 to step S302 is the same as the processing from step S101 to step S102 in FIG. In step S303, the AF processing unit 8 acquires a chromaticity value as attribute information from the saturated pixel region. Unlike the case of the luminance value, the chromaticity value may be acquired for each attribute detection area including a plurality of pixels, or may be acquired for each individual pixel.

  The processing from step S304 to S309 is the same as the processing from step S104 to step S109, except that the attribute information serving as a criterion for determination is changed from a luminance value to a chromaticity value.

  In this way, the point light source focus detection region can be set with attribute information other than the luminance value. Furthermore, the point light source focus detection area may be set using both the luminance value and the chromaticity value. Further, the point light source focus detection region may be set using the chromaticity value of only the saturated pixel region as the attribute information. In this case, different focus detection areas are set for sets of point light sources of different colors.

  In the above example, the luminance value or chromaticity value is classified into two types, but the number of classifications is not limited to two.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. Further, in the description of each operation flowchart described above, the operation is described using “first”, “next”, and the like for convenience, but this does not mean that it is essential to perform the operations in this order. Absent.

  Moreover, each process by embodiment mentioned above can also be memorize | stored as a program which CPU etc. can perform as a computer. In addition, the data can be stored and distributed in a storage medium of an external storage device such as a memory card, a magnetic disk, an optical disk, or a semiconductor memory. The CPU or the like can execute the above-described processing by reading a program stored in the storage medium of the external storage device and controlling the operation by the read program.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

  DESCRIPTION OF SYMBOLS 1 Shooting lens, 2 Lens control part, 3 Imaging device, 4 Imaging control part, 5 Imaging signal processing part, 6 AE processing part, 7 Saturation determination part, 8 AF processing part, 9 Image processing part, 10 Memory, 11 Display part , 12 operation unit, 13 CPU, 81 saturated pixel region setting unit, 82 attribute detection region setting unit, 83 focus detection region setting unit, 84 extraction unit, 85 focus detection unit

Claims (6)

In a focus detection device that calculates a focus position based on an imaging signal of an image sensor that captures a subject image,
A saturation determination unit that determines whether or not the imaging signal is saturated;
A saturated pixel region setting unit that sets a saturated pixel region in which an imaging signal determined to be saturated by the saturation determination unit exists;
An attribute detection area setting unit for setting an attribute detection area inside the saturated pixel area;
A focus detection area that classifies the imaging signals included in the attribute detection area according to attribute information and sets a plurality of focus detection areas including the saturated pixel area based on the position of the imaging signal having the same attribute information A setting section;
An extraction unit that extracts a predetermined signal component from the imaging signal obtained in each of the plurality of focus detection regions;
A focus detection unit that performs focus detection based on the extracted signal components;
A focus detection apparatus comprising:   The focus detection area setting unit classifies luminance values as attribute information of the imaging signal included in the attribute detection area into a plurality of luminance ranges, and the focus is located at a position where luminance values included in the same luminance range exist. The focus detection apparatus according to claim 1, wherein a detection area is set.   The focus detection area setting unit classifies values indicating colors as attribute information of the imaging signal included in the attribute detection area into a plurality of color ranges, and values indicating colors included in the same color range exist. The focus detection apparatus according to claim 1, wherein the focus detection area is set at a position.   The focus detection area setting unit classifies values indicating colors as attribute information of the imaging signal determined to be saturated into a plurality of color ranges, and there are values indicating colors included in the same color range The focus detection apparatus according to claim 1, wherein the focus detection area is set at a position where the focus detection is performed.   The focus detection apparatus according to claim 1, wherein the focus detection area setting unit does not set an area smaller than a predetermined size as the focus detection area. In a focus detection method for calculating a focus position based on an image pickup signal of an image pickup element that picks up a subject image,
Determining whether the imaging signal is saturated;
Setting a saturated pixel region in which an imaging signal determined to be saturated exists;
Setting an attribute detection area inside the saturated pixel area;
Classifying the imaging signals included in the attribute detection area according to attribute information, and setting a plurality of focus detection areas including the saturated pixel area based on the position of the imaging signal having the same attribute information;
Extracting a predetermined signal component from the imaging signal obtained in each of the plurality of focus detection regions;
Performing focus detection based on the extracted signal components;
A focus detection method comprising:

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