JP4946152B2 - Imaging device and its focus adjustment device - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly, to an imaging apparatus having a focus adjustment function for a subject, a focus adjustment apparatus thereof, a processing method therefor, and a program for causing a computer to execute the method.

  In recent imaging apparatuses, the function of selecting an optimal area from a plurality of areas (areas) of a captured image and driving the lens so that the area is in focus is “multi-point autofocus” (or “ It is widely used under the designation of “multi-point ranging autofocus”). Thereby, even when the main subject does not necessarily exist at the center in the angle of view, the photographer can perform appropriate focusing without performing a special operation.

  On the other hand, in order not to miss a photo opportunity, it is very important to shorten the time required for autofocus. For this reason, the function of performing autofocus before the shutter button is pressed is used by the name “monitoring autofocus” (or “moving image autofocus”). If the lens is driven in the vicinity of the in-focus position of the subject in advance, the autofocus operation range for still image shooting can be limited to a narrow range, so the time required for still image autofocus when the shutter button is pressed can be shortened. It can be done.

  However, in order to combine “multipoint autofocus” with “monitoring autofocus”, it is necessary to continue to search for the correct in-focus position after capturing the changing subject and selecting the correct area from multiple areas. There is a problem that the time required for distance measurement and calculation increases as the target area increases.

On the other hand, in order to narrow down the autofocus area, a technique for giving priority to a person has been proposed. For example, by selecting the person facing the front by detecting the state of the person's head, the person is determined as the main subject, the distance is measured with respect to the distance measurement point where the person exists, and the focus is adjusted. Techniques for matching are proposed (see, for example, Patent Document 1). In addition, a technique has been proposed in which areas are prioritized according to luminance information and rough distance distribution information and presented to the photographer, and the photographer selects an appropriate area from the limited areas to narrow down the area. (For example, refer to Patent Document 2).
JP 2001-255455 A (FIG. 2) JP 2001-108886 A (FIG. 5)

  However, in order to recognize the characteristics of the main subject in the prior art, a distance measuring sensor that measures the distance to the imaging device is required. However, this distance measuring sensor is likely to cause an error in the mechanism, and the imaging device This may be a factor that hinders downsizing. On the other hand, if the photographer selects an area as in the prior art, the operation may be complicated.

  Therefore, an object of the present invention is to realize a function of selecting an optimum area from a plurality of areas and continuously focusing without using a distance measuring sensor.

  The present invention has been made to solve the above problems, and a first aspect of the present invention is that imaging means for imaging a subject as a captured image at a predetermined focus position, and a plurality of predetermined multiples of the captured image. An evaluation value generating means for generating an evaluation value of image information for the area; an area selecting means for selecting an area where the maximum value of the evaluation value is estimated to be closest among the plurality of areas; and the area selecting means. A focus operation instructing unit that instructs the subject to focus on the selected area, and when the focus operation instructing unit focuses, the operation is repeated with the focus position as the new predetermined focus position. This is an imaging apparatus. Thereby, the operation of focusing on the area where the maximum value of the evaluation value of the captured image information is estimated to be the closest is repeated, and the focus is finally focused on the area including the closest subject. Bring about an effect.

  In the first aspect, the focus operation instructing unit instructs to perform a wobbling operation at a focused position where focus is achieved, and the region selecting unit estimates a maximum value of the evaluation value based on the wobbling operation. You may do it. Thereby, the detection of the subject based on the wobbling operation is performed.

  In the first aspect, the evaluation value can use a high frequency component of the image information. This is because the data obtained by integrating the high-frequency components of the image information indicates the magnitude of the contrast, and can be basic data for determining whether or not the subject is in focus.

  Further, in the first aspect, the image processing apparatus further comprises image information change detection means for detecting a change in the image information, and when the image information change detection means detects the change in the image information, the region selection means newly adds the above information. You may make it select the area | region estimated that the local maximum of an evaluation value becomes the nearest. As a result, once the closest subject is brought into focus, when a change occurs in the image information, a new region is selected.

  Further, in the first aspect, the zoom means further includes zoom means for enlarging the subject and supplying the subject to the image pickup means, and zoom fluctuation detecting means for detecting a fluctuation of an enlargement ratio by the zoom means. When the means detects the change in the enlargement ratio, the area selecting means may newly select an area where the maximum value of the evaluation value is estimated to be closest. As a result, once the closest subject is brought into focus, when the angle of view changes, the region is newly selected.

  According to a second aspect of the present invention, there is provided an evaluation value generating means for generating an evaluation value of image information for a plurality of predetermined regions of a captured image at a predetermined focus position with respect to a subject, and among the plurality of regions, A region selecting unit that selects a region in which the maximum value of the evaluation value is estimated to be closest, and a focus operation instruction unit that instructs the subject to be focused in the region selected by the region selecting unit. When the focus operation instructing means adjusts the focus, the focus adjustment device repeats the operation with the focus position as the new predetermined focus position. As a result, the operation of focusing on the region where the maximum value of the evaluation value of the image information is estimated to be closest is repeated, and finally the focus is brought to the region including the closest subject. .

  According to a third aspect of the present invention, there is provided a procedure for generating an evaluation value of image information for a plurality of predetermined regions of a captured image at a predetermined focus position with respect to a subject, and the evaluation value of the plurality of regions. A procedure for selecting an area where the local maximum is estimated to be closest, a procedure for instructing the subject to focus on the selected area, and a new focus position when the focus is in focus. And a program for causing a computer to execute a procedure for adjusting the focus, or a procedure for repeating the above steps as the predetermined focus position. As a result, the operation of focusing on the region where the maximum value of the evaluation value of the image information is estimated to be closest is repeated, and finally the focus is brought to the region including the closest subject. .

  According to the present invention, it is possible to obtain an excellent effect that an optimum area can be selected from a plurality of areas and kept in focus without using a distance measuring sensor.

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

  FIG. 1 is a diagram illustrating a configuration example of an imaging apparatus according to an embodiment of the present invention. The imaging apparatus includes a lens group including a surface lens 111, a focus lens 112, and a zoom lens 113 as an optical system. The front lens 111 is a lens for capturing a captured image. The focus lens 112 is a lens for focusing on a subject in the captured image. The zoom lens 113 is a lens for changing the angle of view of the captured image. The positions of the focus lens 112 and the zoom lens 113 are changed by motors 122 and 123, respectively. Drivers 132 and 133 drive these motors 122 and 123.

  The imaging apparatus also includes a focus control unit 142, a zoom control unit 143, a shutter button 152, and a zoom button 153. The focus control unit 142 controls the driver 132 of the focus lens 112. The zoom control unit 143 controls the driver 133 of the zoom lens 113. The shutter button 152 is a button for recording a captured image. The zoom button 153 is a button for adjusting the change in the angle of view by the zoom control unit 143.

  In addition, the imaging apparatus includes an imaging element 160, an imaging signal acquisition unit 170, an image display unit 180, an evaluation value generation unit 190, and a focus adjustment unit 200. The image sensor 160 photoelectrically converts a captured image received via the surface lens 111, the focus lens 112, and the zoom lens 113 and supplies it as an image signal. For example, a CCD (Charge Coupled Devices) or a CMOS (Complementary Metal Oxide) is provided. Semiconductor) sensor. The imaging signal acquisition unit 170 acquires the imaging signal supplied from the imaging element 160, and performs signal processing such as A / D conversion, white balance, and gamma conversion. The image display unit 180 displays the imaging signal acquired by the imaging signal acquisition unit 170 as a captured image, and is realized by, for example, an LCD (Liquid Crystal Display).

  The evaluation value generation unit 190 extracts image information related to high frequency components in a predetermined area (hereinafter referred to as a distance measurement area) of the captured image from the image signal acquired by the imaging signal acquisition unit 170 and generates an evaluation value thereof. Is. The focus adjustment unit 200 selects one of a plurality of distance measurement areas of the captured image based on the evaluation value generated by the evaluation value generation unit 190 and focuses on the distance measurement area. An instruction is given to 142.

  Here, in order to realize autofocus based on an imaging signal without using a distance measuring sensor, a technique using the contrast of the imaging signal is known (see, for example, JP-A-10-213737). . That is, when the contrast is high, the image is in focus, and when the contrast is low, the image is out of focus. The evaluation value generation unit 190 extracts the high frequency component of the imaging signal in a predetermined distance measurement area of the captured image, and determines the magnitude of the contrast by generating data obtained by integrating the high frequency component as an evaluation value of the image information. To do. The focus adjustment unit 200 realizes autofocus by driving the focus lens 112 so that the evaluation value is maximized.

  FIG. 2 is a diagram illustrating a configuration example of the focus adjustment unit 200 according to the embodiment of the present invention. The focus adjustment unit 200 includes an area selection unit 220, a selection area holding unit 230, a focus operation instruction unit 240, a selection area reset unit 250, an image information storage unit 260, an image information change detection unit 270, a focus A control monitoring unit 280 and a zoom position monitoring unit 290 are provided. The focus adjustment unit 200 may be realized as a software program that runs on a computer.

  The area selection unit 220 selects one ranging area from a plurality of predetermined ranging areas of the captured image based on the evaluation value of the image information supplied via the signal line 199. . More specifically, the area selection unit 220 selects an area where the maximum value of the evaluation value is estimated to be closest among a plurality of distance measurement areas at the current position (focus position) of the focus lens 112. In order to perform this region selection, a so-called wobbling operation is performed. In this wobbling operation, the focus lens 112 is slightly vibrated back and forth in the optical axis direction around the current focus position to acquire a change in the captured image. By this wobbling operation, the area selection unit 220 acquires the direction in which the evaluation value of the image information changes, and estimates a region having a maximum value.

  Note that the area selection unit 220 detects the state of the shutter button 152 via the signal line 159. Thereby, for example, when the half-pressed state is obtained, the change of the selection of the distance measurement area may be stopped.

  The selection area holding unit 230 holds information for identifying the distance measurement area selected by the area selection unit 220. The selection area reset unit 250 resets the information held in the selection area holding unit 230 and instructs the area selection unit 220 to reselect the distance measurement area.

  The focus operation instruction unit 240 instructs the focus control unit 142 to drive the focus lens 112 via the signal line 209. More specifically, the focus operation instruction unit 240 focuses on the subject in the distance measurement area held in the selection area holding unit 230 based on the evaluation value of the image information supplied via the signal line 199. Is instructed to move the focus lens 112. In addition, the focus operation instruction unit 240 instructs a wobbling operation for performing a distance measurement area selection by the area selection unit 220 described above.

  The image information storage unit 260 stores image information supplied via the signal line 179. This image information includes luminance information and color information in the imaging signal.

  The image information change detection unit 270 compares the past image information stored in the image information storage unit 260 with the latest image information supplied via the signal line 179 and detects a change in the image information. is there. When detecting a change in image information, the image information change detection unit 270 instructs the selection area reset unit 250 to reset the information held in the selection area holding unit 230.

  The focus control monitoring unit 280 monitors the drive control of the focus lens 112 via the signal line 149. When the focus control monitoring unit 280 detects that the operation of the focus lens 112 has stopped, the focus control monitoring unit 280 instructs the image information storage unit 260 to store the latest image information supplied via the signal line 179.

  The zoom position monitoring unit 290 monitors the position of the zoom lens 113 via the signal line 148. When the zoom position monitoring unit 290 detects that the position of the zoom lens 113 has changed, the zoom position monitoring unit 290 instructs the selection area reset unit 250 to reset the information held in the selection area holding unit 230.

  FIG. 3 is a diagram showing an example of a plurality of distance measuring areas on the captured image in the embodiment of the present invention. In this example, two ranging areas 611 and 612 are defined on the captured image. In this case, the area selection unit 220 selects any one of the ranging areas 611 and 612 and holds information for identifying the selected ranging area in the selection area holding unit 230.

  Here, assuming that a person's face is contained in the distance measurement area 611 as shown in the figure and a tree is contained in the distance measurement area 612 behind the person, the distance measurement area 611 In 611 and 612, for example, the distribution of evaluation values as shown in FIG. 4 is shown.

  The area selection unit 220 sets all the ranging areas that “the evaluation value increases when the focus lens is moved to the closest side” as a candidate for the ranging area to be finally focused by the wobbling operation. If there is only one candidate, the distance measuring area that is the candidate is selected. Further, when there are a plurality of candidate ranging areas, for example, (1) a distance measuring area closer to the center is selected, (2) an area having a large fluctuation amount of the wobbling evaluation value is selected, (3) Prioritize color information and select a ranging area that contains a lot of specific colors (when many people are included as subjects) or a ranging area that does not contain a lot of specific colors (when subjects contain lots of sky), Alternatively, it is possible to adopt a method such as (4) selecting one distance measurement area based on a criterion of selecting at random. In addition, when using color information, there is a method of selecting only one including specific color information from a distance measuring area “an evaluation value increases when the focus lens is moved to the closest side”. By such a method, it becomes possible to match the closest subject among the specific subjects.

  However, there is a possibility that a noise component may be included in the difference between the evaluation values due to the wobbling operation. Therefore, it is necessary to set a certain level threshold value and to trust the result of the wobbling direction determination only when the threshold value is exceeded. . Also, when the evaluation value fluctuation due to wobbling is extremely large, there is a possibility of disturbance such as camera shake or temporary entry of the subject due to panning or tilting, so such information is not used. It is necessary to do so. For the same reason, when the evaluation value direction determination does not indicate the same direction more than a certain number of times even though the wobbling center is located at the same position, the evaluation value should not be used.

  Note that if it is determined that any evaluation value is unreliable due to low contrast, disturbance, or the like, autofocus is executed using the distance measurement area selected immediately before. Furthermore, if any of the evaluation values is not reliable and there is no distance measurement area selected so far, for example, auto focus is executed in the distance measurement area closest to the center.

  FIG. 4 is a diagram illustrating an example of an evaluation value distribution by a plurality of distance measurement areas on a captured image according to the embodiment of the present invention. 4A and 4B both show the evaluation value of the image information in the vertical direction and the focus position of the focus lens 112 in the horizontal direction. As for the focus position, the right side is the closest side and the left side is the infinite side. In this example, the distribution is such that the subject in the distance measurement area 611 is closer to the subject than the subject in the distance measurement area 612.

  When the focus position is at the current position in FIG. 4A, the evaluation value gradient 712 of the distance measurement area 612 indicates that the evaluation value gradient 712 is climbing to the closest side, while the evaluation value gradient 711 of the distance measurement area 611 is substantially flat. It has become. Accordingly, the area selection unit 220 selects the distance measurement area 612 by estimating that the evaluation value of the distance measurement area 612 has a maximum value on the near side of the current position in FIG. As a result, under the instruction from the focus operation instruction unit 240, autofocus is performed with reference to the distance measuring area 612, and the focus position is moved to the current position in FIG.

  When the focus position is at the current position in FIG. 4B, the evaluation value slope 713 of the distance measurement area 611 indicates climbing to the closest side, while the evaluation value inclination 714 of the distance measurement area 612 is a local maximum value. Is shown. Therefore, the area selection unit 220 selects the distance measurement area 611 by estimating that the evaluation value of the distance measurement area 611 has a maximum value on the closest side of the current position in FIG. As a result, under the instruction from the focus operation instruction unit 240, autofocus is performed based on the distance measurement area 611. That is, the inclination of the ranging area 611 that could not be found at the current position in FIG. 4A is found at the current position in FIG.

  In this way, the focus position is adjusted so that the subject on the closest side is in focus. Here, an example in which two distance measurement areas are provided in the center of the captured image has been described. However, the present invention is not limited to this, and an arbitrary number of distance measurement areas are provided at arbitrary positions as shown below. be able to.

  FIG. 5 is a diagram showing another example of a plurality of distance measuring areas on a captured image in the embodiment of the present invention. FIG. 5A shows an example in which three distance measuring areas are arranged at the center of the captured image. In the case of this example, either one of the left and right ranging areas is selected as being close. If only one distance measuring area is provided at the center, the background behind is in focus, and people on both sides are blurred. In this regard, by providing three distance measuring areas as shown in FIG. 5A, such a void can be prevented.

  FIG. 5B is an example in which the ranging area is spread so as to cover the entire captured image. According to this example, a close subject can be detected with high accuracy. However, the cost for generating the evaluation value increases according to the number of ranging areas. Therefore, for example, the number of distance measurement areas may be reduced by not providing distance measurement areas in the peripheral portion of the captured image.

  In any case, the distance measurement area provided in the captured image needs to match the distance measurement area of the autofocus of the still image.

  FIG. 6 is a diagram illustrating an example in which a plurality of contrasts are included in one of the distance measurement areas on the captured image according to the embodiment of the present invention. FIG. 6A is an example in which two distance measuring areas are provided in the center of the captured image as in the case of FIG. 3, but it is assumed that the subject in the distance measuring area 621 is both a person and a background. To do.

  In this case, the evaluation value distribution in the distance measuring area 621 has two peaks as shown in FIG. Therefore, at the current position in FIG. 6B, since the slope 621 of the distance measuring area 621 indicates mountain climbing and the slope 622 of the distance measuring area 622 indicates mountain climbing, the distance measuring area 622 is closer. Presumed to be on the side.

  In this regard, in the embodiment of the present invention, since the area selection unit 220 determines the selection of the distance measurement area again at the focus position at which the distance measurement area 622 is maximized, the distance measurement area 621 is finally at the closest side. Mountains will be detected.

  As described above, according to the embodiment of the present invention, ranging is performed by wobbling until there is no other ranging area where there is a mountain of evaluation values closer to the closer side than the current ranging area. The area is detected, and the operation of moving to the peak of the evaluation value of the distance measurement area is repeated. As a result, the focus lens 112 moves the second time from the first time, the third time from the second time, and the third time from the second time so as to focus on a subject that is closer to the imaging device. The number of areas gradually decreases, and finally, a distance measuring area in which the closest subject exists is selected.

  In this way, if autofocus is performed in the finally selected distance measuring area and the camera is on standby, the focus lens 112 has already been moved to a position where the focus lens 112 should be finally moved when the shutter button 152 is pressed. 112 is present, so autofocus can be executed in a very narrow focus range after the shutter button 152 is pressed, or capture can be performed without newly executing autofocus. Realized in a short time.

  In addition, when the range between the infinity side and the near side limit of the focus lens 112 is driven without selecting any ranging area, whether the imaging area is occupied by a low-contrast subject without contrast, It is considered too dark to autofocus. Therefore, in such a case, it is necessary to wait at a predetermined position (for example, about 2 meters from the imaging device or the infinity side), or to reduce the moving speed of the focus lens 112 and wait for the appearance of the subject, or the contrast signal is the highest. Move to a higher point and wait.

  Next, a response when the subject changes will be described. When autofocus is executed and there is no subject on the near side, it is advantageous from the viewpoint of power consumption to stop the operation of the focus lens 112. However, there is no subject closest to the selected ranging area due to movement of the subject, intrusion of the subject from outside the angle of view of the imaging device, movement of the imaging device, etc. while the focus lens 112 is stopped. If you fall into a problem, you will not be able to detect it

  In order to avoid such a problem, image information when the focus lens 112 is stopped is stored in the image information storage unit 260, and the image information change detection unit 270 detects a change in the image information. When the image information changes by a predetermined value or more, the area selection unit 220 is prompted to select a distance measurement area via the selection area reset unit 250. Here, the image information includes luminance information and color information. Accordingly, for example, when the luminance level is decreased or increased by a predetermined ratio or more, or when the color temperature has changed by a predetermined ratio or more, the ranging area selection is performed.

  It is desirable to acquire these pieces of image information from the entire screen divided into a plurality of screens. However, the closer to the center, the lower the change determination threshold value may make the center redetection determination more sensitive.

  In some cases, the subject has just passed the angle of view, so if the image information changes and the original image information is restored after a certain period of time, it is just the subject that has passed. Therefore, it will not move to the closest side. However, in consideration of the noise component, it is determined that the original image information has been restored if the original image information falls within a certain threshold value after a certain period of time.

  Even when the position of the zoom lens 113 is moved, there is a possibility that the subject does not exist in the distance measuring area that has been selected so far due to the change in the angle of view, so it is necessary to select the distance measuring area again. There is. Therefore, the zoom position monitoring unit 290 monitors the movement of the zoom lens 113, and when the movement is detected, prompts the area selection unit 220 to select a distance measurement area via the selection area reset unit 250.

  Note that when the wobbling is continued without stopping the focus lens 112, the above-described problem does not occur, and thus these measures are unnecessary.

  Next, the operation of the imaging apparatus according to the embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a diagram illustrating a processing procedure of the imaging apparatus according to the embodiment of the present invention. First, in the focus adjustment unit 200, the area selection unit 220 selects a distance measurement area candidate (step S911). As a result, when a distance measurement area candidate is selected (step S912), autofocus is performed in the selected distance measurement area under an instruction from the focus operation instruction unit 240 (step S913).

  After autofocus is performed in step S913, the area selection unit 220 selects a distance measurement area candidate at the focus position (step S914). As a result, when another candidate for the distance measurement area is selected (step S915), autofocus is performed in the newly selected distance measurement area under an instruction from the focus operation instruction unit 240 (step S913). ). As described above, this operation is repeated as long as another candidate for the distance measurement area is selected.

  On the other hand, if no ranging area candidate is selected in step S912, autofocus is performed under the instruction from the focus operation instruction unit 240 in the provisional area provisionally selected in step S936 described later (step S912). S916). As a result, if autofocus is possible (step S917), the area selection unit 220 selects a distance measurement area candidate at the focus position (step S914). If autofocus is not possible (step S917), the subject appears at a predetermined position (for example, about 2 meters from the imaging device or on the infinity side) or the moving speed of the focus lens 112 is decreased. Or move to a point with the highest contrast signal and wait (step S918).

  After entering the standby state in step S918, or after no other ranging area candidate is selected in step S915, the process proceeds to a state in which the change of the subject is monitored (step S919).

  FIG. 8 is a diagram showing a processing procedure for subject change monitoring (step S919) in the embodiment of the present invention. When stopping the wobbling operation, the image information storage unit 260 stores the image information according to an instruction from the focus control monitoring unit 280 (step S942). Then, the image information change detection unit 270 detects a subsequent change in the image information (step S943). That is, the image information change detection unit 270 detects the change from the difference by comparing the image information stored in the image information storage unit 260 with the latest image information. At this time, as described above, since the subject may have just passed the angle of view, if a certain level of change occurs after a certain time (step S944), the area selection unit 220 performs distance measurement based on the wobbling operation. An area candidate is selected (step S946). As a result, when another candidate for the distance measurement area is selected in accordance with the change of the subject (step S947), the flow returns to the flowchart of FIG. 7 and the focus operation instruction unit 240 performs the operation in the selected distance measurement area. Under the instruction, autofocus is performed (step S913). On the other hand, if there is no change in the subject and no other ranging area candidate is selected (step S947), the wobbling operation is continued and the change in the subject is monitored.

  On the other hand, if the wobbling operation is to be continued (step S941), the area selection unit 220 continues to select a distance measurement area candidate based on the wobbling operation without detecting a change in the image information (step S946).

  FIG. 9 is a diagram showing a processing procedure for distance measurement area candidate selection (steps S911, S914, and S942) in the embodiment of the present invention. The focus operation instruction unit 240 instructs the start of the wobbling operation (step S921). Then, whether or not each of the ranging areas can be a candidate is determined as follows.

  The area selection unit 220 acquires the evaluation value of the ranging area during the wobbling operation (step S922), and whether or not the evaluation value increases when the focus lens is moved to the close side, that is, the subject is on the close side. It is determined whether or not it exists (step S923). When it is determined that the subject exists, if the evaluation value is reliable (step S924), the distance measurement area is set as a candidate (step S925). Here, the criterion for determining whether or not it is reliable is as described above, and it can be determined that it is reliable when the fluctuation is not extremely large and exceeds a certain level threshold. On the other hand, if there is no subject on the close side (step S923) or the evaluation value is not reliable (step S924), the distance measurement area is excluded from the candidates (step S926). When these determinations are made for all the ranging areas (step S927), the focus operation instruction unit 240 instructs the end of the wobbling operation (step S928).

  As a result, when a plurality of ranging areas are candidates (step S931), one of the highest priority is selected (step S932). As a priority order in that case, as described above, for example, the one having a large variation in the evaluation value is given priority. On the other hand, when there is only one candidate for the distance measurement area (step S933), the candidate is selected (step S934). If no distance measurement area candidate is found and no distance measurement area has been selected in the past (step S935), a specific distance measurement area such as a distance measurement area close to the center is selected as a temporary area. (Step S936).

  As described above, according to the embodiment of the present invention, auto-focusing is performed according to an instruction from the focus operation instruction unit 240 in the distance measurement area selected by the area selection unit 220, and the area selection unit 220 is further at the focus position. By repeatedly selecting the distance measurement area according to the above, it is possible to finally focus on the closest subject.

  In the embodiment of the present invention, as the number of distance measurement areas as candidates in the area selection unit 220 increases, it becomes possible to focus on a close subject more reliably. As one method for that purpose, it is conceivable to set the aperture in the direction of aperture as much as possible. As a result, the depth of field is deepened, and even when the focus lens 112 is located away from the focus of the subject, the presence of the subject can be sensed and it is easy to find the closest subject.

  As another method, it is conceivable to increase the wobbling amount so that evaluation values of other distance measurement areas can be easily detected when the maximum value of the evaluation value is reached in a certain distance measurement area. If wobbling is too large, focus will not be achieved and the angle of view will be noticeable. However, in the monitoring state in which no moving image is recorded, the image is visually recognized only through a relatively small screen such as an LCD. In this case, even if wobbling is increased, it is not noticeable. Therefore, when the maximum point of the evaluation value is reached, if the moving image is not being recorded, the focus operation instruction unit 240 controls to increase the size of the wobbling, thereby affecting the user. This makes it easier to find nearby subjects. The switching of the wobbling size may be changed according to the zoom position, or may be changed according to the depth of field.

  The embodiment of the present invention is an example for embodying the present invention and has a corresponding relationship with the invention-specific matters in the claims as shown below, but is not limited thereto. However, various modifications can be made without departing from the scope of the present invention.

  The processing procedure described in the embodiment of the present invention may be regarded as a method having a series of these procedures, and a program for causing a computer to execute these series of procedures or a recording medium storing the program May be taken as

It is a figure which shows the example of 1 structure of the imaging device in embodiment of this invention. It is a figure which shows the example of 1 structure of the focus adjustment part 200 in embodiment of this invention. It is a figure which shows an example of the several ranging area on the captured image in embodiment of this invention. It is a figure which shows an example of the evaluation value distribution by the some ranging area on the captured image in embodiment of this invention. It is a figure which shows the other example of several ranging area on the captured image in embodiment of this invention. It is a figure which shows the example in which several contrast is contained in one of the ranging areas on the captured image in embodiment of this invention. It is a figure which shows the process sequence of the imaging device in embodiment of this invention. It is a figure which shows the process sequence of object change monitoring in embodiment of this invention. It is a figure which shows the process sequence of ranging area candidate selection in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 111 Surface lens 112 Focus lens 113 Zoom lens 122, 123 Motor 132, 133 Driver 142 Focus control part 143 Zoom control part 152 Shutter button 153 Zoom button 160 Imaging element 170 Imaging signal acquisition part 180 Image display part 190 Evaluation value generation part 200 Focus Adjustment unit 220 Area selection unit 230 Selection area holding unit 240 Focus operation instruction unit 250 Selection area reset unit 260 Image information storage unit 270 Image information change detection unit 280 Focus control monitoring unit 290 Zoom position monitoring unit

Claims (8)

Imaging means for imaging a subject as a captured image at a predetermined focus position;
Zoom means for enlarging the subject and supplying the image to the imaging means;
Zoom fluctuation detecting means for detecting fluctuations in the enlargement ratio by the zoom means;
Evaluation value generating means for generating evaluation values of image information for a plurality of predetermined regions of the captured image;
Wherein when allowed to minute vibration back and forth in the optical axis direction of the focus lens around a predetermined focus position, one of the difference component of the evaluation value by the minute vibration in the respective area of the plurality of regions of a predetermined A region selection means for selecting a region where the maximum value of the evaluation value is estimated to be the closest among the plurality of regions only when the threshold value is exceeded,
Focusing operation instruction means for instructing the subject to focus in the area selected by the area selection means,
When the zoom variation detecting unit detects the variation of the enlargement ratio, the region selecting unit newly selects a region where the maximum value of the evaluation value is estimated to be closest,
An imaging apparatus that repeats the operation with the focus position set as the new predetermined focus position when the focus operation instruction means adjusts the focus. The focus operation instruction means instructs to perform a wobbling operation at a focused position in focus,
The imaging apparatus according to claim 1, wherein the region selection unit estimates a maximum value of the evaluation value based on the wobbling operation.   The imaging apparatus according to claim 1, wherein the evaluation value includes a high frequency component of the image information. Further comprising image information change detecting means for detecting a change in the image information,
The imaging apparatus according to claim 1, wherein when the image information change detection unit detects a change in the image information, the region selection unit newly selects a region where the maximum value of the evaluation value is estimated to be closest. Input means for inputting a captured image obtained by imaging a subject at a predetermined focus position;
Zoom fluctuation detecting means for detecting a fluctuation of an enlargement ratio in the zoom means for enlarging the subject and supplying it to the imaging means;
Evaluation value generating means for generating evaluation values of image information for a plurality of predetermined regions of the captured image;
Wherein when allowed to minute vibration back and forth in the optical axis direction of the focus lens around a predetermined focus position, one of the difference component of the evaluation value by the minute vibration in the respective area of the plurality of regions of a predetermined A region selection means for selecting a region where the maximum value of the evaluation value is estimated to be the closest among the plurality of regions only when the threshold value is exceeded,
Focusing operation instruction means for instructing the subject to focus in the area selected by the area selection means,
When the zoom variation detecting unit detects the variation of the enlargement ratio, the region selecting unit newly selects a region where the maximum value of the evaluation value is estimated to be closest,
An image processing apparatus that repeats an operation when the focus operation instruction means adjusts the focus, with the focus position as a new predetermined focus position. Evaluation value generation means for generating evaluation values of image information for a plurality of predetermined regions of a captured image at a predetermined focus position with respect to a subject;
Zoom fluctuation detecting means for detecting a fluctuation of an enlargement ratio in the zoom means for enlarging the subject and supplying it to the imaging means;
Wherein when allowed to minute vibration back and forth in the optical axis direction of the focus lens around a predetermined focus position, one of the difference component of the evaluation value by the minute vibration in the respective area of the plurality of regions of a predetermined A region selection means for selecting a region where the maximum value of the evaluation value is estimated to be the closest among the plurality of regions only when the threshold value is exceeded,
Focusing operation instruction means for instructing the subject to focus in the area selected by the area selection means,
When the zoom variation detecting unit detects the variation of the enlargement ratio, the region selecting unit newly selects a region where the maximum value of the evaluation value is estimated to be closest,
A focus adjustment device that repeats the operation when the focus operation instruction means adjusts the focus, using the focus position as a new predetermined focus position. A procedure for generating an evaluation value of image information for a plurality of predetermined regions of a captured image at a predetermined focus position with respect to a subject;
Wherein when allowed to minute vibration back and forth in the optical axis direction of the focus lens around a predetermined focus position, one of the difference component of the evaluation value by the minute vibration in the respective area of the plurality of regions of a predetermined A procedure for selecting a region where the maximum value of the evaluation value is estimated to be the closest among the plurality of regions only when the threshold value is exceeded,
A procedure for detecting a change in an enlargement ratio in zoom means for enlarging the subject and supplying the image to the imaging means;
A procedure for selecting a region where the maximum value of the evaluation value is estimated to be closest when a change in the enlargement ratio is detected;
Instructing the subject to focus on the selected area; and
A focus adjustment method comprising: a step of repeating each of the steps with the focus position set as a new predetermined focus position when the focus is achieved. A procedure for generating an evaluation value of image information for a plurality of predetermined regions of a captured image at a predetermined focus position with respect to a subject;
Wherein when allowed to minute vibration back and forth in the optical axis direction of the focus lens around a predetermined focus position, one of the difference component of the evaluation value by the minute vibration in the respective area of the plurality of regions of a predetermined A procedure for selecting a region where the maximum value of the evaluation value is estimated to be the closest among the plurality of regions only when the threshold value is exceeded,
A procedure for detecting a change in an enlargement ratio in zoom means for enlarging the subject and supplying the image to the imaging means;
A procedure for selecting a region where the maximum value of the evaluation value is estimated to be closest when a change in the enlargement ratio is detected;
Instructing the subject to focus on the selected area; and
A program for causing a computer to execute a procedure for repeating each of the steps with the focus position as a new predetermined focus position when the focus is in focus.

Images