JP5482454B2 - Imaging apparatus, focus control method, and program - Google Patents

Description

The present invention relates to an imaging apparatus such as a digital camera having an autofocus function, it relates to a focus control how Ho及 beauty program.

  2. Description of the Related Art Conventionally, in a camera device having an autofocus function, a technique that enables correction of a focus shift by a manual operation after a so-called focus lock is performed at the time of shooting until a final shooting instruction operation is known ( For example, see Patent Document 1 below).

JP-A-11-174314

  However, although it is possible to correct the focus shift after the focus lock by using the above technique, there are problems that the focus shift cannot be corrected instantaneously by manual operation, and that manual operation is troublesome in the first place.

The present invention has been made in view of such a conventional problem, and requires manual operation for defocusing at the time of shooting due to the movement of the camera body after focusing once by the autofocus function. imaging device it is possible to not immediately corrected, and to provide a focus control direction Ho及 beauty program.

In order to solve the above-described problem, in the imaging apparatus according to the first aspect of the present invention, an imaging unit that images a subject, and a control unit that controls the focus lens to move to a focus position in response to a predetermined operation; An image acquisition device that acquires movement information of the image pickup apparatus main body after the control means is controlled to move the focus lens to the in-focus position, and the image pickup apparatus based on the movement information acquired by the information acquisition means. Is determined by the control means to determine whether or not the subject has moved away from or closer to the subject when the focus lens is moved to the in-focus position, and the determination means determines that the imaging apparatus has moved away from the subject. Then, the imaging device is moved forward by the first search range setting means for setting the search range of the focus lens on the far side and the determination means. When it is determined that the subject is approaching, second search range setting means for setting the search range of the focus lens to the near distance side, the first search range setting means, and the second search range setting means. wherein while moving the focus lens in the search ranges set by searching the focus position, and a correcting means for correcting the position of the searched focus focus lens position, the control means, the still image shooting instruction The focus lens is automatically controlled to the in-focus position in response to a focus lock operation prior to the operation, and the correction means corrects the position of the focus lens in response to a still image shooting instruction operation .

In the focus control method according to the fifth aspect of the present invention, the focus control method using the imaging device is a control step of controlling the focus lens to move to the in-focus position in response to a predetermined operation. And an information acquisition step of acquiring movement information of the main body of the imaging device after the focus lens is controlled to move to the in-focus position by the control means, and based on the movement information acquired by the information acquisition step, A determination step of determining whether the imaging device has moved away from or approached the subject when the focus lens has been moved to the in-focus position by the control step, and that the imaging device has moved away from the subject by the determination step When the determination is made, a first search range setting step for setting the search range of the focus lens to the long distance side. And a second search range setting step for setting a search range of the focus lens to a short distance side when the determination step determines that the imaging apparatus has approached the subject, and the first search A correction step of searching for a focus position while moving the focus lens within the search range set by the range setting step and the second search range setting step, and correcting the position of the focus lens to the searched focus position; viewed including the control step, a response to the focus lens to focus lock operation prior to imaging instruction of a still image is automatically controlled to the focus position, the correction step, the position of the response to the focus lens in the photographing instruction operation of the still image It is characterized by correcting .

According to a sixth aspect of the present invention, there is provided a program for controlling a computer to move a focus lens to a focus position in response to a predetermined operation, and the focus lens is moved to a focus position by the control means. After the control to move to, the information acquisition means for acquiring the movement information of the main body of the imaging apparatus, and the focus lens is focused by the control means based on the movement information acquired by the information acquisition means. Determination means for determining whether or not the subject is moved away from or closer to the position When the determination means determines that the imaging apparatus has moved away from the subject, the search range of the focus lens is set to a long distance. The first search range setting means set on the side and the determination means determine that the imaging apparatus has approached the subject. Then, the focus is set within the search range set by the second search range setting means, the first search range setting means, and the second search range setting means for setting the search range of the focus lens to the short distance side. The in-focus position is searched while moving the lens and functions as a correction means for correcting the position of the focus lens at the searched in-focus position, and the control means performs a focus in response to a focus lock operation prior to a still image shooting instruction. The lens is automatically controlled to the in-focus position, and the correction unit corrects the position of the focus lens in response to a still image shooting instruction operation .

  According to the present invention, it is possible to immediately correct a focus shift at the time of shooting due to the movement of the camera body after the focus is once adjusted by the autofocus function without requiring a manual operation.

It is a block diagram of a digital camera common to each embodiment according to the present invention. It is a conceptual diagram which shows a focus position-distance table. It is a flowchart which shows the operation | movement in 1st Embodiment. It is explanatory drawing which shows the positional relationship of the to-be-photographed object and camera at the time of imaging | photography. It is explanatory drawing which shows the to-be-photographed object distance at the time of half-pressing of a shutter key, and the time of full pressing, and the movement distance of a triaxial direction. It is a flowchart which shows the operation | movement in 2nd Embodiment. It is a flowchart which shows the 1st search range limited contrast AF process common to 2nd and 3rd embodiment. It is a flowchart which shows the operation | movement in 3rd Embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing an outline of an electrical configuration of a digital camera 1 common to each embodiment described below. The digital camera 1 has a still image shooting mode and a moving image shooting mode as shooting modes, and mainly includes the following units as shown in the figure.

  That is, the digital camera 1 includes a lens block 2 made of an optical system including a focus lens, a motor block 3 made of a focus motor for driving the optical system, and a motor driver 4 for driving the focus motor. . The motor driver 4 drives the focus motor in accordance with a command from the CPU 5 that controls the entire digital camera 1, and moves the optical system along the optical axis according to the control of the CPU 5 to change the position of the focus lens.

  The digital camera 1 also has a CCD 6 (imaging means) that converts an optical image of a subject imaged through the lens block 2 into an electrical signal (imaging signal). The CCD 6 is driven by a vertical / horizontal driver 8 based on a timing signal generated by a timing generator (TG) 7 in accordance with a command from the CPU 5 and outputs an analog imaging signal corresponding to the optical image of the subject. The output signal of the CCD 6 is subjected to noise reduction by correlated double sampling and converted into a digital signal in the CDS / AD circuit 9 and then output to the image processing unit 10.

  The image processing unit 10 generates R, G, and B color component data (hereinafter, RGB data) for each pixel based on the input digital imaging signal (Bayer data) using the SDRAM 11 as a working memory in accordance with a command from the CPU 5. RGB interpolation processing, YUV conversion processing for generating YUV data consisting of luminance signals (Y) and color difference signals (U, V) from RGB data for each pixel, and digital for improving image quality such as auto white balance and edge enhancement Perform signal processing.

  The YUV data converted by the image processing unit 10 is sequentially stored in the SDRAM 11 and is converted into a video signal each time one frame of data is accumulated and sent to a liquid crystal monitor (LCD) 12, where it is displayed as a through image on the screen. Is done.

  Further, when shooting is performed with the shutter key (full pressing operation in this embodiment) in the still image shooting mode, the image data temporarily stored in the SDRAM 11 is compressed by the CPU 5, and finally the still image of a predetermined format is stored. It is recorded in the external memory 13 as an image file. During moving image shooting in the moving image shooting mode, a plurality of image data stored in the SDRAM 11 at a predetermined frame rate is sequentially compressed by the CPU 5 and finally recorded as a moving image file in the external memory 13.

  The external memory 13 is composed of, for example, various memory cards, and the still image file and the moving image file recorded in the external memory 13 are read and expanded as needed by the CPU 5 according to the user's selection operation in the playback mode, and YUV After being developed as data on the SDRAM 11, it is reproduced and displayed on a liquid crystal monitor (LCD) 12.

  The digital camera 1 also includes a flash memory 14 that is a non-volatile memory capable of rewriting stored data. In the flash memory 14, various programs for causing the CPU 5 to control the respective units, that is, programs for performing AE control, AF control, AWB control, and the like based on luminance information included in the imaging signal, and the control thereof Stores various data used. In the AF control, the contrast value of the subject image, that is, the AF evaluation value by the imaging signal output from the CCD 6 is acquired while moving the focus lens in the optical axis direction, and the peak position (focusing position) where it becomes the largest is obtained. This is based on a known contrast detection method in which focusing is performed by moving the focus lens.

  In the present embodiment, the flash memory 14 has a focus control for causing the CPU 5 to function as the focus control means, the movement distance acquisition means, the focus correction means, the distance acquisition means, the distance calculation means, and the in-focus position acquisition means of the present invention. A program and data constituting the focus position-distance table 101 shown in FIG. 2 are stored. The focus position-distance table 101 is table information indicating the subject distance and the position of the focus lens in the lens block 2 corresponding to the subject distance (hereinafter simply referred to as a focus position), and is focused at a certain focus position. A focus distance required to focus on a subject at a certain shooting distance is shown at the same time as a shooting distance to the subject that can be performed. That is, the flash memory 14 is a table information storage unit.

  A microcomputer 15 is connected to the CPU 5. The microcomputer 15 is connected to a key input unit 16 and an acceleration sensor 17 including a shutter button (not shown), a power key, a mode switch, a zoom up / zoom down button, and the like. The microcomputer 15 constantly scans the key input unit 16 for various switches and the like. When any operation key is operated by the user, an operation signal corresponding to the operation content is sent from the microcomputer 15 to the CPU 5. Sent to.

  The shutter button has a so-called half-shutter function that can be operated in two steps, a half-press operation and a full-press operation (shooting instruction operation). During shooting, it is also used as a recording start (movie start) key.

  The acceleration sensor 17 is a detection unit of the present invention that individually detects acceleration in the three-axis directions of x, y, and z as motion information indicating the motion of the camera body, and the detection signal of the acceleration sensor 17 is a microcomputer 15. Is sent to the CPU 5 via. The acceleration sensor 17 has a camera body in which the z axis coincides with the optical axis of the lens block 2, the x axis coincides with the left and right direction of the camera body, and the y axis coincides with the up and down direction of the camera body. It is arranged in the body (see FIG. 4).

  The digital camera 1 also has a power supply control circuit 19 for controlling the power of a rechargeable battery 18 such as a nickel metal hydride battery to a predetermined voltage required in each unit described above and supplying the power to each unit. The operation of the power supply control circuit 19 is controlled by the microcomputer 15.

  Next, an operation according to the present invention of the digital camera 1 having the above configuration will be described. FIG. 3 is a flowchart showing the processing contents of the CPU 5 when the still image shooting mode is set.

  When the still image shooting mode is set, the digital camera 1 repeatedly performs the imaging operation of the subject by the CCD 6 at a predetermined cycle, and the captured subject image is sequentially displayed on the liquid crystal monitor 12 as a through image.

  In the meantime, as shown in FIG. 3, the CPU 5 sequentially checks whether or not the shutter key is half-pressed, and when the shutter key is half-pressed (YES in step SA1), normal AF processing by the contrast detection method is started ( In step SA2), the AF process is continued until the main subject A (FIG. 4) is in focus (NO in step SA3). When focus is finally reached (YES in step SA3), the subject distance L corresponding to the focus position at that time is stored in the work memory with reference to the focus position-distance table 101 (FIG. 2) described above. (Step SA4).

  Subsequently, the acceleration sensor 17 detects triaxial acceleration (step SA5), and calculates the movement distance (ΔLx, ΔLy, ΔLz) of the camera body in the triaxial direction based on the detection result (step SA6). The processes in steps SA5 and SA6 are repeated until the shutter key is fully pressed (NO in step SA7). Meanwhile, the focus position is maintained at the position controlled by the AF process in step SA2. That is, the focus lock state is maintained.

  Here, the movement distances (ΔLx, ΔLy, ΔLz) calculated in step SA6 are the movement distances of the camera body (left or right, up) In the second and subsequent processes, calculation is performed to add / subtract the current travel distance to the previous travel distance. The calculated movement distances (ΔLx, ΔLy, ΔLz) are sequentially stored in the work memory.

Thereafter, when the shutter key is fully pressed (YES in step SA7), the subject distance (L) stored in the work memory and the movement distances (ΔLx, ΔLy, ΔLz) in the three axes directions, that is, half-pressing operation are performed. Based on the final moving distance from the time when the corresponding AF processing is completed, the appropriate subject distance (L ′) is set to L ′ = √ {(L + ΔLz) ² + ΔLx ² + ΔLy ² }.
(Step SA8, see FIG. 5).

  Then, a focus position corresponding to the calculated appropriate subject distance (L ′) is acquired from the focus position-distance table 101, and the focus lens is moved to the acquired position (step SA9). In other words, the focus shift caused by the movement of the camera body after halfway pressing of the shutter key is corrected, and in this state, the photographing process (imaging process for recording) is performed and the photographed image is recorded in the external memory 13 (step SA10). . Thereafter, the process returns to the above-described step SA1 to repeat the above-described processing. Although not shown, if the half-pressed state is released after the shutter key is pressed halfway and before the shutter key is fully pressed, the process immediately returns to step SA1.

  As described above, in this embodiment, even when the focus is shifted due to the movement of the camera body while in the focus lock state, when the shutter key is fully pressed, it is detected sequentially after the focus lock. The focus position is controlled according to the appropriate subject distance (L ′) calculated from the movement distance of the camera body in the three axis directions. That is, the focus is automatically corrected.

  In addition, in this case, unlike a normal AF process using a contrast detection method when the shutter key is half-pressed, the focus lens is a known position (focus position) corresponding to an appropriate subject distance (L ′). Therefore, the focus correction is performed at a high speed.

  Therefore, even when the focus is out of focus after the focus is locked, it is possible to immediately correct the out-of-focus at the time of photographing without requiring manual operation.

  In the present embodiment, the appropriate subject distance (L ′) described above is calculated when the shutter key is fully pressed, but it is sequentially performed until the shutter key is fully pressed. It may be. That is, the above-described processing in step SA8 may be performed immediately after step SA6.

  Further, the process of moving the focus lens to a position corresponding to the appropriate subject distance (L ′) in step SA9 is performed immediately after calculating the subject distance (L ′) following the process of step SA6 (that is, immediately before step SA7). ). In other words, in this embodiment, the focus position controlled by the AF processing accompanying the half-pressing operation of the shutter key is corrected all at once when the shutter key is fully pressed, but until the shutter key is fully pressed. You may make it carry out sequentially between.

(Embodiment 2)
Next, a second embodiment will be described. In the present embodiment, in the digital camera 1 having the configuration shown in FIG. 1, when the still image shooting mode is set in the flash memory 14, the CPU 5 controls the focus control unit, the movement distance acquisition unit, the focus correction unit, and the like. A focus control program for functioning as a distance acquisition unit, a distance calculation unit, and a search range determination unit and for performing the processing of FIG. 6 is stored.

  Hereinafter, the processing contents of the CPU 5 will be described with reference to FIG. When the still image shooting mode is set, the CPU 5 performs focusing by a normal AF process using a contrast detection method in response to a half-press operation of the shutter key, and acquires and stores the subject distance L from the focus position at that time. (Steps SB1 to SB4). Thereafter, the acceleration sensor 17 sequentially detects triaxial accelerations (step SB5), and calculates the movement distances (ΔLx, ΔLy, ΔLz) of the camera main body based on the detection results (step SB6). Subsequently, an appropriate subject distance (L ′) is immediately calculated based on the calculated movement distances (ΔLx, ΔLy, ΔLz) and the subject distance (L) stored in the work memory (step SB7).

  Note that the movement distances (ΔLx, ΔLy, ΔLz) calculated in step SB6 are the movement distances (left or right direction) of the camera body based on the point in time when the focusing process by the AF process described above is completed, as in the first embodiment. , Upward or downward, forward or backward travel distance), and in the second and subsequent processing, calculation is performed by adding and subtracting the current travel distance to the previous travel distance, and the calculated travel distance (ΔLx, ΔLy, ΔLz) are sequentially stored in the working memory. The method for calculating the subject distance (L ′) is the same as in the first embodiment.

  Then, until the shutter key is fully pressed (NO in step SB8), the CPU 5 repeats steps SB5 to SB7 to sequentially acquire an appropriate subject distance (L ′). Meanwhile, the focus position is maintained at the position controlled by the AF process in step SB2. That is, the focus lock state is maintained.

  Thereafter, when the shutter key is fully pressed (YES in step SB8), whether or not the appropriate subject distance (L ′) acquired immediately before is larger than the subject distance (L) stored in the work memory. Is determined (step SB9). If the determination result is YES and it can be determined that the camera body is further away from the subject than when the shutter key is half-pressed, a first search range priority AF process described later is performed. If the determination result in step SB9 is NO, and it can be determined that the camera body is closer to the subject than when the shutter key is half-pressed, the second described later is performed. The search range priority AF process is performed (step SB11).

  FIG. 7 is a flowchart showing the first search range priority AF process by the CPU 5. In the first search range priority AF processing, the initial search range when searching for the focus position while moving the focus lens is set to the far side (the subject is far), and the far side is preferentially searched. This is an AF process using a contrast detection method.

  In such AF processing, first, the focus lens is moved by one step so as to move the focus position to the far side (step SB101), and imaging processing and AF evaluation value are detected (step SB102). Then, the peak of the AF evaluation value cannot be confirmed, that is, it cannot be confirmed that the AF evaluation value has changed from the increasing tendency to the decreasing tendency (NO in step SB103), and the search range for a predetermined number of steps determined in advance. If the movement of the focus lens to the far distance side is not yet completed (NO in step SB104), the process returns to step SB101, and the movement of the focus lens to the far distance side and the detection of the AF evaluation value are repeated.

  In the above process, the AF evaluation value detected in step SB102 described above is stored in the working memory for a predetermined number of times, and in step SB103, the peak is confirmed based on the AF evaluation values for the immediately preceding multiple times. Try.

  After that, if it can be confirmed from the AF evaluation value detected in step SB102 while the above process is repeated that it has changed from an increasing tendency to a decreasing tendency (YES in step SB103), the AF evaluation value peaked. The focus lens is moved to the position (step SB108), and the AF process is completed.

  On the other hand, when the peak of the AF evaluation value cannot be confirmed and the movement of the focus lens to the far side has been completed while the processing of steps SB101 to SB104 is repeated, for example, the focus position is the limit position on the far side. (NO in step SB103, YES in SB104), the focus lens is moved by one step so as to move the focus position to the short distance side (step SB105), and the AF evaluation value is detected (step SB106). ). If the AF evaluation value peak cannot be confirmed (NO in step SB107), the process returns to step SB105, and the movement of the focus lens to the short distance side and the detection of the AF evaluation value are repeated.

  When the focus lens is moved by one step in step SB105 for the first time, the focus lens is once returned to the position at the time when the first search range priority AF processing is started, and then the focus lens is moved by one step. . The method for confirming the peak of the AF evaluation value in step SB107 is the same as that in step SB103 described above.

  After that, if the peak of the AF evaluation value can be confirmed from the AF evaluation value detected in step SB106 while repeating the above process (YES in step SB107), the focus lens is moved to the position where the AF evaluation value is at the peak. (Step SB108), and the AF process is completed.

  On the other hand, the above-described second search range priority AF process is different from the above-described first search range priority AF process in that the initial search range when searching for the focus position while moving the focus lens is closer to the short distance side. This is an AF process using a contrast detection method that is set to (close to the subject) and preferentially searches the near distance side. Although a specific processing procedure is not shown, the moving direction of the focus lens during the processing shown in FIG. 7 is reversed.

  When either of the first or second search range priority AF processing described above is completed, shooting processing (recording imaging processing) is performed and the shot image is recorded in the external memory 13 (step SB12). Thereafter, the process returns to step SB1 described above and the above-described processing is repeated. Although not shown, if the half-pressed state is released after the shutter key is pressed halfway and before the shutter key is fully pressed, the process immediately returns to step SB1.

  As described above, in the present embodiment, even when the focus is shifted due to the movement of the camera body while in the focus lock state, when shooting is performed with the shutter key fully pressed, The focus position is controlled by the second search range priority AF process. That is, the focus is automatically corrected.

  In addition, in the first and second search range priority AF processes, an appropriate subject that has been sequentially calculated based on the subject distance (L) when the focus is locked and the movement distance of the camera body in the three-axis directions during the focus lock. The AF processing (focus correction) is performed at high speed by setting the range in which the focus position is preferentially searched based on the distance (L ′) to the range on the far side or the near side.

  Therefore, even when the focus is out of focus after the focus is locked, it is possible to immediately correct the out-of-focus at the time of photographing without requiring manual operation.

  In the present embodiment, the appropriate subject distance (L ′) is sequentially calculated while the focus is locked. However, as in the first embodiment, it is calculated when the shutter key is fully pressed. Also good.

  Further, after the shutter key is fully pressed, the first search range priority AF process or the second search range priority AF process is always performed, but the following may be performed. For example, immediately before step SB9, it is determined whether or not the difference between the subject distances L and L ′ is within a specified allowable range, that is, whether or not the subject distances L and L ′ are substantially the same. If it is determined that they are substantially the same, the shooting / recording process of step SB12 may be immediately performed without performing the first or second search range priority AF process.

  Further, either the first search range priority AF process or the second search range priority AF process is performed according to the comparison result of both the subject distances L and L ′, that is, a range in which the focus position is preferentially searched. Although AF processing is performed on the far side or near side, the following may be performed. That is, the AF processing performed according to the comparison result of both the subject distances L and L ′ is the AF processing in which the search range of the focus lens is limited to the far side or the near side, and an appropriate subject distance (L ′) is focused. When the subject distance (L) at the time of locking is greater than the subject distance (L) at the time of locking, AF processing is performed by limiting the search range of the focus lens to the far side, and the appropriate subject distance (L ′) L) If it is less than or equal to, AF processing may be performed in which the search range of the focus lens is limited to the short distance side.

(Embodiment 3)
Next, a third embodiment will be described. In this embodiment, in the digital camera 1 having the configuration shown in FIG. 1, when the moving image shooting mode is set in the flash memory 14, the CPU 5 controls the focus control unit, the movement distance acquisition unit, the focus correction unit, and the distance of the present invention. A focus control program for functioning as an acquisition unit, a distance calculation unit, and a search range determination unit and for performing the processing of FIG. 8 is stored.

  Hereinafter, the processing contents of the CPU 5 will be described with reference to FIG. In the moving image shooting mode, the CPU 5 sequentially checks whether or not the movie start key (shutter key) is pressed, and when the movie start key is pressed (YES in step SC1), starts normal AF processing by the contrast detection method (step S1). SC2), AF processing is continued until focus is achieved (NO in step SC3). When focus is finally reached (YES in step SC3), movie recording (imaging, compression, and recording of a frame image at a predetermined frame rate) is started (step SC4). At that time, the subject distance L corresponding to the focus position at that time is stored in the working memory with reference to the focus position-distance table 101 (FIG. 2) described above (step SC5).

  Subsequently, the acceleration sensor 17 detects the acceleration in the triaxial direction, calculates the movement distance (ΔLx, ΔLy, ΔLz) of the camera body based on the detection result (step SC6), and further, for each frame (predetermined) The AF evaluation value is acquired from the image pickup signal (which may be the frame interval) (step SC7). If there is no change in the acquired AF evaluation value, the processes in steps SC6 and SC7 are repeated (NO in step SC8). Meanwhile, the focus position is maintained at the position controlled by the AF process in step SC2. That is, the focus lock state is maintained.

  Here, the movement distances (ΔLx, ΔLy, ΔLz) in the three-axis directions calculated in step SC6 are the points when the focusing by the above-described AF process of step SC2 (or the AF process of step SC11 or SC12 described later) is completed. Is the movement distance of the camera body (left or right direction, upward or downward direction, forward or backward movement distance), and in the second and subsequent processing, the movement distance up to the previous movement distance Calculate to add or subtract. The calculated movement distances (ΔLx, ΔLy, ΔLz) are sequentially stored in the work memory.

  In step SC8, the peak AF evaluation value at the time of the AF process in step SC2 (or the AF process in step SC11 or SC12 described later) is stored in the work memory, and the AF evaluation value and step The presence or absence of a change in the AF evaluation value is determined by comparing the AF evaluation value acquired in SC7. In such determination, “no change” if the difference between the AF evaluation value stored in the working memory and the AF evaluation value acquired in step SC7 is within a predetermined allowable range, and “ It is judged that there is a change.

  Thereafter, if the AF evaluation value changes during movie recording (YES in step SC8), first, the subject distance (L) at the start of movie recording stored in the work memory and the movement distance in the three-axis directions An appropriate subject distance (L ′) is calculated based on (ΔLx, ΔLy, ΔLz), that is, the final moving distance from the point when the AF process in step SC2 (or step SC11 or SC12) is completed (step SC9). Thereafter, it is determined whether or not the calculated appropriate subject distance (L ′) is greater than the subject distance (L) stored in the work memory (step SC10).

  If the determination result is YES and it can be determined that the camera body is further away from the subject than the movie recording start time, the first search range of FIG. 7 described in the second embodiment is used. When the priority AF process is performed (step SC11) and the determination result in step SC10 is NO and it can be determined that the camera body is closer to the subject than the movie recording start time, the second embodiment is used. The described second search range priority AF process is performed (step SC12).

  When either the first or second search range priority AF processing is completed, the process returns to step SC5, and the subject distance (L) corresponding to the new focus position controlled by any AF processing is determined as the focus position-distance. After obtaining from the table 101 (FIG. 2) and storing it in the working memory, the processing from step SC6 onward is repeated.

  As described above, in this embodiment, when the focus adjusted by the AF processing at the start of movie recording or the subsequent AF processing is shifted due to the movement of the camera body during recording, this is a change in the AF evaluation value. At that time, the focus position is controlled by the first or second search range priority AF processing. That is, the focus is automatically corrected.

  In addition, in the first and second search range priority AF processes, it is calculated from the subject distance (L) at the start of recording and the movement distance in the three-axis direction of the camera body that is sequentially detected after the movie recording starts. Based on the appropriate subject distance (L ′), the focus position search range is given priority to the far side or the near side, so that the AF process (focus correction) is performed at high speed.

  Therefore, even when the focus is shifted during movie recording, it is possible to immediately correct the focus shift at the time of shooting without requiring manual operation.

  In the present embodiment, the appropriate subject distance (L ′) described above is calculated when the AF evaluation value changes during movie recording. However, it is calculated regardless of whether the AF evaluation value changes. It may be performed sequentially during recording. That is, the process of step SC9 described above may be performed immediately after step SC6. In this case, only the calculation process of the appropriate subject distance (L ′) may be periodically performed at a period different from the frame rate.

  Further, as described above, the moving distance (ΔLx, ΔLy, ΔLz) of the camera body calculated in step SC6 is not set as the moving distance based on the point in time when the immediately preceding AF process is completed, but the movie recording start point is always set. The first or second search range priority AF processing is performed based on the comparison result between the subject distance (L) initially acquired at the start of movie recording and the appropriate subject distance (L ′) as the reference moving distance. You may make it perform.

  Further, the first or second search range priority AF process is performed only at the timing when the AF evaluation value changes. However, the AF process may be performed at a predetermined time interval, for example, every frame. .

  In step SC7, the acquired AF evaluation value is stored in the working memory. In step SC8, the previous AF evaluation value acquired in step SC7 and the current AF evaluation acquired in step SC7 are stored. The values may be compared, and the first or second search range priority AF processing may be performed when both AF evaluation values have changed. In this case, whether or not there is a change between the previous AF evaluation value and the current AF evaluation value may be strictly determined.

  Also, the focus position is given priority according to the comparison result between the subject distance (L) acquired at the time of AF processing at the start of movie recording or the subsequent AF processing and the appropriate subject distance (L ′) described above. Although the AF process is performed with the search range set to the long distance side or the short distance side, as described in the second embodiment, the AF process is performed according to the comparison result of both the object distances L and L ′. The focus lens search range may be limited to the far side or the near side. That is, when the appropriate subject distance (L ′) is larger than the subject distance (L) at the time of the immediately preceding AF process, the AF process is performed by limiting the search range of the focus lens to the far side, and the appropriate subject is obtained. When the distance (L ′) is equal to or less than the subject distance (L) at the time of the immediately preceding AF process, the AF process in which the focus lens search range is limited to the short distance side may be performed.

  Here, in the first to third embodiments, the digital camera 1 that does not have the optical zoom function has been described, but the present invention can also be applied to a camera that has the optical zoom function. However, when the configuration of the imaging optical system is such that the relationship between the subject distance and the focus position changes when the optical zoom magnification is different, the focus position-distance table shown in FIG. A focus position-distance table having a data structure indicating the relationship between the subject distance and the focus position for each optical zoom magnification is used.

  In any case, the focus position-distance table (101) is not necessarily used, and a focus position corresponding to an appropriate subject distance (L ′) may be obtained by calculation. .

  Although the present invention has been described with reference to the case where the present invention is applied to a digital camera having a general configuration, the present invention is not limited to this, and other information such as a mobile phone terminal can be used as long as the present invention has an autofocus function. The present invention can also be applied to other camera devices such as a digital camera built in the device and a digital video camera.

1 Digital Camera 2 Lens Block 3 Motor Block 4 Motor Driver 5 CPU
6 CCD
10 Image processing unit 11 SDRAM
14 Flash memory 16 Key input unit 17 Acceleration sensor 101 Focus position-distance table L Subject distance L ′ Appropriate subject distance ΔLx Movement distance in the X axis direction ΔLy Movement distance in the Y axis direction ΔLz Movement distance in the Z axis direction

Claims (6)

Imaging means for imaging a subject;
Control means for controlling the focus lens to move to the in-focus position in response to a predetermined operation;
Information acquisition means for acquiring movement information of the imaging apparatus main body after the control means is controlled to move the focus lens to the in-focus position;
A determination unit that determines whether the imaging apparatus has moved away from or approached the subject when the focus lens is moved to the in-focus position by the control unit, based on the movement information acquired by the information acquisition unit;
A first search range setting unit configured to set a search range of the focus lens to a long distance side when the determination unit determines that the imaging apparatus has moved away from the subject;
A second search range setting unit that sets a search range of the focus lens to a short distance side when the determination unit determines that the imaging apparatus has approached the subject;
The focus position is searched while moving the focus lens within the search range set by the first search range setting means and the second search range setting means, and the position of the focus lens is corrected to the searched focus position. and a correction means that,
The control means automatically controls the focus lens to the in-focus position in response to a focus lock operation prior to a still image shooting instruction,
The image pickup apparatus , wherein the correction unit corrects the position of the focus lens in response to a still image shooting instruction operation . Distance acquisition means for acquiring a first subject distance at the time when the focus lens is controlled to move to the in-focus position by the control means;
Distance storage means for storing the first subject distance acquired by the distance acquisition means;
A moving distance calculating unit that calculates a moving distance of the imaging apparatus after the focus lens is controlled to move to the in-focus position based on the movement information acquired by the information acquiring unit;
Distance calculating means for calculating a second subject distance based on the first subject distance stored in the distance storage means and the moving distance calculated by the moving distance calculating means;
The distance determination unit determines whether the second subject distance calculated by the distance calculation unit is larger or smaller than the first subject distance stored in the distance storage unit, so that the imaging apparatus Determine if you ’re moving away or approaching the subject,
The first search range setting means sets the search range of the focus lens on the side farther from the subject when the distance determination means determines that the second subject distance is larger than the first subject distance. ,
The second search range setting means sets the search range of the focus lens closer to the subject when the distance determination means determines that the second subject distance is smaller than the first subject distance. The imaging apparatus according to claim 1. Table information storage means for storing table information indicating a correspondence relationship between the position of the focus lens and a pre-known subject distance in which each position is an in-focus position;
The imaging apparatus according to claim 2, wherein the distance storage unit stores the subject distance based on table information stored in the table information storage unit. The correction means has a maximum contrast value of the subject image captured by the imaging means while moving the focus lens within the search range set by the first search range setting means and the second search range setting means. become focus position searching the image pickup apparatus according to any one of claims 1 to 3, characterized in that to correct the position of the searched focus focus lens position. A focus control method using an imaging device,
A control step for controlling the focus lens to move to the in-focus position in response to a predetermined operation;
An information acquisition step of acquiring movement information of the imaging apparatus main body after the control unit is controlled to move the focus lens to the in-focus position;
A determination step of determining whether the imaging apparatus is moving away from or approaching the subject when the focus lens is moved to the in-focus position by the control step, based on the movement information acquired by the information acquisition step;
A first search range setting step for setting a search range of the focus lens to a long distance side when it is determined by the determination step that the imaging apparatus has moved away from the subject;
A second search range setting step for setting a search range of the focus lens to a short distance side when it is determined in the determination step that the imaging apparatus has approached the subject;
The focus position is searched while moving the focus lens within the search range set by the first search range setting step and the second search range setting step, and the position of the focus lens is corrected to the searched focus position. only contains a correction step that,
The control step automatically controls the focus lens to the in-focus position in response to a focus lock operation prior to a still image shooting instruction,
The focus control method characterized in that the correction step corrects the position of the focus lens in response to a still image shooting instruction operation . Computer
Control means for controlling the focus lens to move to the in-focus position in response to a predetermined operation;
Information acquisition means for acquiring movement information of the main body of the imaging apparatus after the control means is controlled to move the focus lens to the in-focus position;
A determination unit that determines whether the imaging apparatus has moved away from or approached the subject when the focus lens is moved to the in-focus position by the control unit, based on the movement information acquired by the information acquisition unit;
A first search range setting unit that sets a search range of the focus lens to a long distance side when the determination unit determines that the imaging apparatus has moved away from the subject;
A second search range setting unit that sets a search range of the focus lens to a short distance side when the determination unit determines that the imaging apparatus has approached the subject;
The focus position is searched while moving the focus lens within the search range set by the first search range setting means and the second search range setting means, and the position of the focus lens is corrected to the searched focus position. to function as a correction means that,
The control means automatically controls the focus lens to the in-focus position in response to a focus lock operation prior to a still image shooting instruction,
The correction means corrects the position of the focus lens in response to a still image shooting instruction operation .

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