JP2013205787A - Focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing device able to estimate an appropriate focusing position according to a status of a subject.SOLUTION: A scanning operation is repeated (S17), positional information of a focus lens that has the peak of image contrast is detected and stored (S41). In accordance with the detection result of the scanning operation performed at last, a determination is made whether to estimate a focusing position at a specific time (S51 and S53). If the final focusing position can be used for the estimation of a focusing position (Yes in S53), a focusing position at a specific time is estimated based on the stored past positional information (S63). If the final focusing position cannot be used (No in S53), a focusing position in the final scan is estimated (S55). Then, based on the plurality of pieces of stored past positional information and the estimated focusing position, the focusing position at the specific time is estimated.

Description

  The present invention relates to a focus adjustment apparatus, and more particularly to a focus adjustment apparatus that performs focusing by moving a focus lens to a position where the contrast of an image reaches a peak based on imaging data obtained from an imaging element.

  In the case of a moving subject, even if the subject is in focus, the subject may move during the shutter time lag after the shutter release button is operated, resulting in an out-of-focus photograph. In view of this, there is known a focus adjustment device that predicts a focus position during main exposure based on a plurality of distance measurement results performed until the shutter release button is operated. For this reason, in the case of focus adjustment by the phase difference method, the focus position is predicted based on a history of a plurality of detected defocus amounts, and in the case of focus adjustment by the contrast method, a plurality of detected in-focus states are predicted. The focus position is predicted based on the position history (see Patent Document 1).

JP 2010-107711 A

  Since the focus adjusting apparatus as described above predicts the in-focus position at the time of the main exposure, it is possible to reduce the possibility of being out of focus. However, in the case of focus adjustment by the contrast method, unlike the case of the phase difference method, since the peak of the contrast value is detected while actually moving the focus lens, it takes time to determine the focus position. End up. For this reason, when the movement of the subject is fast, the prediction accuracy of the in-focus position is lowered, and there is a possibility that the number of out-of-focus pictures will be increased. In addition, depending on the subject, the focus position may not be predicted during the main exposure based on the past focus history.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a focus adjustment device capable of predicting an appropriate in-focus position according to the state of a subject.

  In order to achieve the above object, a focus adjustment apparatus according to a first aspect of the present invention includes a focus lens that can be moved in the optical axis direction by a lens driving unit and forms an image of light from a subject to perform focus adjustment of a photographing optical system. In the apparatus, an imaging element that obtains imaging data of the subject imaged by the imaging optical system, and a plurality of imaging data output by the imaging element by performing an imaging operation by the imaging element by moving the focus lens And a control unit that performs a scanning operation for detecting the position of the focus lens at which the contrast peak of the image is based on the image, and the control unit repeatedly executes the scanning operation until immediately before the main exposure. The position information of the focus lens at which the contrast of the peak reaches is detected and stored, and based on the stored plurality of past position information A prediction control unit that predicts a focus position at a fixed time, and a focus position at a predetermined time based on the plurality of stored past position information according to the detection result of the scan operation performed immediately before the main exposure. A determination unit that determines whether or not to predict.

  According to a second aspect of the present invention, in the first aspect of the invention, the determination unit performs a scan operation immediately before the main exposure and the latest position information of the plurality of stored past position information. When the difference from the position of the focus lens at the time of completion is larger than the first predetermined value, it is determined that the in-focus position at the predetermined time is not predicted based on the past position information.

  According to a third aspect of the present invention, there is provided a focus adjustment apparatus according to the first aspect, further comprising a time storage unit that detects and stores a time at which the focus lens position at which the contrast of the image reaches a peak is detected by executing the scan operation. The determination unit is configured to detect a time at which the latest position information among a plurality of past position information stored in the time storage unit is detected, and a time at which the scanning operation is terminated immediately before the main exposure. When the difference is larger than the second predetermined value, it is determined that the focus position at the predetermined time is not predicted based on the past position information.

  According to a fourth aspect of the present invention, in the first aspect, the control unit controls the main exposure operation by the image sensor, and the determination unit performs a scan operation performed immediately before the main exposure. When predicting an in-focus position at a predetermined time based on the stored plurality of past position information according to the detection result, the prediction control unit performs the imaging based on the stored plurality of past position information. The focus lens is moved by predicting the focus position at the main exposure time by the element.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the determination unit uses the stored plurality of past position information according to the detection result of the scanning operation performed immediately before the main exposure. When determining that the in-focus position at a predetermined time is not predicted based on the above, the control unit sets the position of the focus lens at the time of main exposure to the position of the focus lens at the end of the scan operation executed immediately before the main exposure. To do.

  According to a sixth aspect of the present invention, there is provided a focus adjustment apparatus according to the first aspect, wherein the focus is adjusted by a photographing optical system that includes a focus lens that can be moved in the optical axis direction by the lens driving unit and forms an image of light from a subject. In the adjustment device, an imaging device that obtains imaging data of the subject imaged by the imaging optical system, and an imaging operation by the imaging device is performed by moving the focus lens, and a plurality of imagings output by the imaging device And a control unit that performs a scanning operation for detecting the position of the focus lens where the contrast peak of the image is based on the data, and the control unit repeatedly executes the scanning operation until immediately before the main exposure, and The position information of the focus lens where the contrast of the image reaches a peak is detected and stored, and based on a plurality of stored past position information. Even if the position of the focus lens at which the contrast of the image reaches a peak cannot be detected by the prediction control unit that predicts the in-focus position at a predetermined time and the scan operation performed immediately before the main exposure, A peak estimation unit that estimates the position of the focus lens, and the prediction control unit is a focus lens position that is a peak estimated by the peak estimation unit, the stored past position information, or the peak estimation The focus position at a predetermined time is calculated based on both the focus lens position that is the peak estimated by the unit and the stored past position information.

  According to the present invention, it is possible to provide a focus adjustment device capable of predicting an appropriate in-focus position according to the state of a subject.

1 is a block diagram mainly showing an electrical configuration of a camera according to an embodiment of the present invention. 6 is a flowchart showing a basic operation (single-shooting AF) of a camera according to an embodiment of the present invention. 6 is a flowchart illustrating a basic operation (continuous shooting AF) of a camera according to an embodiment of the present invention. It is a flowchart which shows the operation | movement of the scan control of the camera which concerns on one Embodiment of this invention. It is a flowchart which shows the operation | movement of the focusing position calculation of the camera which concerns on one Embodiment of this invention. It is a flowchart which shows the operation | movement of the final focusing position availability determination of the camera which concerns on one Embodiment of this invention. It is a flowchart which shows the operation | movement of focus position estimation in the last scan of the camera which concerns on one Embodiment of this invention. It is a graph which shows an example of control of the lens position when prediction is possible in the camera concerning one embodiment of the present invention. 6 is a graph illustrating an example of lens position control when prediction is impossible in the camera according to the embodiment of the present invention. 6 is a graph illustrating an example of control of in-focus position implementation in a final scan in a camera according to an embodiment of the present invention.

  A preferred embodiment will be described below using a camera to which the present invention is applied according to the drawings. The camera according to a preferred embodiment of the present invention is a digital camera, and includes a focus lens that can be moved in the optical axis direction by a lens driving unit to form an image of light from a subject and perform focus adjustment of the photographing optical system.

  That is, the camera according to the present embodiment includes an imaging unit, and the imaging unit converts the subject image into image data, and the display unit arranges the subject image on the back of the main body based on the converted image data. Live view display. The photographer determines the composition and the photo opportunity by observing the live view display.

  In addition, when continuous AF is set, a contrast value is acquired based on image data from the imaging unit, the time when the contrast value reaches the in-focus position, and the in-focus position of the focus lens. Remember the history. At the time of the release operation or subsequent continuous shooting, the focus position at the time of the main exposure is predicted based on the focus history in consideration of the time lag. If the predicted focus position is greatly deviated from the current position, or if the difference between the latest focus time and the current time is large, the reliability of the predicted focus position is low. Therefore, the current lens position is set as the in-focus position. When image data is acquired by the main exposure, the image data is subjected to image processing and recorded on a recording medium. The image data recorded on the recording medium can be reproduced and displayed on the display unit when the reproduction mode is selected.

  FIG. 1 is a block diagram mainly showing an electrical configuration of a camera according to an embodiment of the present invention. The camera according to the present embodiment includes an interchangeable lens 100 and a camera body 200, and both are detachable via a mount unit (not shown). In this embodiment, the interchangeable lens type is used. However, it is of course possible to fix the lens barrel to the camera body.

  The interchangeable lens 100 includes a photographing lens 101, a motor driving unit 102, a lens control unit 103, and a storage unit 104. The photographing lens 101 includes optical lenses such as a focus lens and a zoom lens, and forms a subject image by a photographing optical system constituted by these optical lenses. The motor drive unit 102 has a drive source such as a motor, and moves the focus lens along the optical axis direction of the photographing optical system.

  The lens control unit 103 includes a lens CPU and its peripheral circuits. The lens CPU controls the interchangeable lens 100 in accordance with a program stored in the storage unit 104 and a control command from the main body CPU in the main body control unit 204 on the camera main body 200 side. As the control, for example, the scanning operation of the photographing lens 101, the driving to the in-focus position, and the like are performed via the motor driving unit 102 in accordance with a command from the main body control unit 204. Further, the current state of the focus lens and zoom lens, the lens state during the scanning operation, and the like are detected and transmitted to the camera body 200 side as lens data. In addition to the above-described program, the storage unit 104 also stores unique information such as optical information of the interchangeable lens 100, adjustment values at the time of factory shipment, and the like.

  The camera body 200 includes an image sensor 201, a liquid crystal display unit 202, a storage unit 203, a body control unit 204, and an operation unit 205. The imaging element 201 is disposed on the optical axis of the photographing lens 101 and in the vicinity of the imaging position of the subject image, and the subject image is photoelectrically converted by a plurality of pixels arranged two-dimensionally to obtain image data (also referred to as imaging data). Is output to the main body control unit 204.

  The main body control unit 204 includes a main body CPU and its peripheral circuits. The main body CPU controls the entire camera according to the program stored in the storage unit 203. Various circuits such as an image processing circuit, a contrast AF circuit, an expansion / compression circuit, and a communication circuit are provided as peripheral circuits in the main body control unit 204. The contrast AF circuit receives the image data from the image sensor 201 and obtains the contrast value of the subject image by obtaining a difference signal between adjacent pixels.

  Further, the main body control unit 204 outputs a control command such as a scan operation command, a focus position movement command, and a lens data request command to the lens control unit 103 via the communication circuit to the lens control unit 103 described above. . The main body control unit 204 also receives optical data, lens data such as the state of the interchangeable lens 100 from the lens control unit 103.

  In addition, the main body control unit 204 moves the focus lens in the photographing lens 101 to execute an imaging operation by the imaging element 201, and a focus at which an image contrast peak occurs based on a plurality of imaging data output by the imaging element 201. It functions as a control unit that performs a scanning operation for detecting the position of the lens. The control unit repeatedly executes a scanning operation to detect and store position information of the focus lens at which the contrast of the image reaches a peak, and predicts a focus position at a predetermined time based on a plurality of stored past position information. Whether to predict the in-focus position at a predetermined time based on a plurality of stored past position information in accordance with the prediction control section (see S63 in FIG. 5 described later) and the detection result of the scan operation executed last. It also has a function as a determination unit (see S57 of FIG. 5 described later) for determining whether or not.

  In addition, the main body control unit 204, as the determination unit described above, has a difference between the latest position information of the plurality of stored past position information and the position of the focus lens detected by the last scan operation performed. If it is larger than the predetermined value, it is determined that the in-focus position at the predetermined time is not predicted based on the past position information (see S71 in FIG. 6 described later).

  Further, the main body control unit 204, as the above-described determination unit, detects the difference between the time when the latest position information among a plurality of past position information is detected and the time when the focus lens position is detected by the lastly executed scanning operation. Is larger than the second predetermined value, it is determined that the in-focus position at the predetermined time is not predicted based on the past position information (see S73 in FIG. 6 described later).

  Further, the main body control unit 204 controls the main photographing operation by the image sensor 201. As a determination unit described above, when a focus position at a predetermined time is predicted based on a plurality of stored past position information in accordance with the detection result of the scan operation executed last (see S53 in FIG. 5 described later). The prediction control unit predicts the in-focus position at the main photographing time by the image sensor based on the stored plurality of past position information (see S63 in FIG. 5 described later), and moves the focus lens (described later). S21 in FIG.

  In addition, the main body control unit 204 determines, as the above-described determination unit, that the in-focus position at a predetermined time is not predicted based on a plurality of stored past position information in accordance with the detection result of the lastly executed scan operation. In this case (S53 No. in FIG. 5 to be described later), as the above-described control unit, the position of the focus lens at the time of actual photographing is set as the position of the focus lens at the end of the last scan operation (see S59 in FIG. 5).

  Further, the main body control unit 204 is configured to estimate a peak focus lens position (to be described later) even when the focus lens position where the image contrast reaches a peak cannot be detected by the last scan operation. (See S55 in FIG. 5 and S83 in FIG. 7). Further, as the above-described prediction control unit, the focus lens position that is the peak estimated by the peak estimation unit or the stored past position information, or the focus lens position that is the peak estimated by the peak estimation unit and the past position information stored Based on both of these, the focus position at a predetermined time is calculated (see S57 Yes → S61 → S63 in FIG. 5).

  The storage unit 203 in the camera body 200 includes various memories such as a rewritable volatile memory such as a RAM, a rewritable nonvolatile memory such as a flash memory, and a loadable storage medium. The nonvolatile memory stores various data for adjustment in addition to the program for the main body CPU. In addition, image data of a captured image that has been subjected to image processing by the main body control unit 204 is recorded in the storage medium. In addition, the storage unit 203 functions as a time storage unit that detects and stores the time at which the focus lens position at which the contrast of the image reaches a peak is detected by executing a scanning operation. It should be noted that the function as the time storage unit may of course be configured such that the main body control unit 204 incorporates a temporary storage unit and this temporary storage unit fulfills the function.

  The liquid crystal display unit 202 includes a liquid crystal monitor disposed on the back surface of the camera body 200. The liquid crystal display unit 202 performs live view display based on the image data from the image sensor 201, performs playback display based on the captured image data read from the storage unit 203, and sets various shooting modes. A menu image or the like is displayed. Note that the monitor is not limited to the liquid crystal monitor, and other monitors such as an organic EL may be used.

  The operation unit 205 includes various operation members such as a release button, a power button, a menu button, an OK button, a cross button, and the operation state of these operation members is output to the main body control unit 204. The main body control unit 204 executes camera control in response to an operation signal from the operation unit 205.

  Next, the operation in this embodiment will be described with reference to the flowcharts shown in FIGS. These flowcharts are executed by the main body control unit 204 in accordance with a program stored in the storage unit 203. The focus adjustment operation in the present embodiment is an operation when continuous AF (also referred to as C-AF) is set on the menu screen.

  The continuous AF in the present embodiment is applied to single shooting and continuous shooting. In single shooting, when the release button in the operation unit 205 is pressed, the main exposure is performed once and the image data is recorded in the storage unit 203. In continuous shooting, the main exposure is repeated at predetermined time intervals while the release button is pressed, and the image data acquired in the main exposure is sequentially recorded in the storage unit 203. Single shooting and continuous shooting are set on a menu screen or the like.

  When the single shooting mode is set and the release button is half-pressed, the single shooting AF flow shown in FIG. 2 starts. When the single shooting flow is entered, first, scan control is executed (S1). Here, the lens control unit 103 in the interchangeable lens 100 is started to drive the focus lens to the near side or the infinity side by the motor driving unit 102, and image data (imaging image) from the image sensor 201 is moved during the movement of the focus lens. Based on the data, the contrast AF circuit in the main body control unit 204 calculates a contrast value. The focus position of the focus lens when the contrast value reaches a peak is calculated, and a focus history including a set of the focus position and the focus time is recorded in the storage unit 203. Detailed operation of this scan control will be described later with reference to FIG.

  When the scan control is performed, it is determined whether a 2nd release is detected (S3). Since the 2nd release switch is turned on when the release button in the operation unit 205 shifts from half-press to full-press, this step is determined based on the state of the 2nd release switch. As a result of this determination, if the 2nd release is not detected, that is, if the release button is not fully pressed, the process returns to step S1 to continue the scan control.

  If the result of determination in step S3 is that 2nd release has been detected, focus drive is carried out (S5). Here, using the in-focus history stored in the scan control in step S1, the time lag until the main exposure is taken into consideration, and during the main exposure (when half of the time from the start of exposure to the end of exposure has elapsed) The in-focus position is predicted, and the focus lens is moved to the in-focus position predicted by the lens control unit 103 and the motor driving unit 102. When the reliability of the predicted position is low, the focus lens is moved to the final focus position.

  Once focus driving is performed in step S5, next exposure is performed (S7). Here, exposure control is performed with an aperture value, shutter speed value, and the like for appropriate exposure, image processing is performed on the image data obtained by the image sensor 201 at this time, and the image data subjected to this image processing is stored. Recorded in the unit 203. When the main exposure is finished, the flow of the single-shot AF is finished.

  Next, continuous shooting AF will be described using the flowchart shown in FIG. If the release button is fully pressed while the continuous shooting mode is set, the flow of continuous shooting AF shown in FIG. 3 starts. If the continuous shooting flow is entered, first, the main exposure is performed (S11). Here, image processing is performed on the image data obtained in the same manner as in step S 7 in FIG. 2, and this image data is recorded in the storage unit 203.

  Once the main exposure is performed in step S11, next, initial position driving is performed (S13). In step S17, which will be described later, scan control is performed. When the scan control is started, the focus lens position is driven to an optimum position. That is, in contrast AF, the peak of the contrast value is detected, but the focus lens is moved to the peak of the contrast value during the main exposure in step S11. It is desirable to start scanning in contrast AF from a position slightly shifted from the peak position. Therefore, in this step, the driving is performed so that the position slightly shifted from the peak position of the contrast value becomes the initial position in consideration of the driving direction of the focus lens so far.

  Once the initial position driving is performed in step S13, next, exposure conditions for scanning are determined (S15). Here, the exposure conditions for the scan control performed in step S17 are determined. In determining the exposure condition, the image data obtained at the previous main exposure or the image data of the live view image is taken in, the luminance information is calculated from the image data, and the exposure condition (for example, electronic shutter speed) during scanning is calculated. Etc.).

  Once the exposure condition is determined in step S15, next, scan control is performed (S17). Here, as in step S1 in FIG. 2, the contrast value is acquired while moving the focus lens. Detailed operation of this scan control will be described later with reference to FIG. In continuous shooting AF, main exposure and scan control are repeated while the release button is fully pressed. Scan driving is performed for a predetermined number of frames (that is, performed with the number of frames within a range not exceeding the upper limit).

  If scan control is performed in step S17, then the in-focus position is calculated (S19). Here, as in step S5 of FIG. 2, the focus position stored in the scan control in step S17 is used, and the focus position during the main exposure is considered in consideration of the continuous shooting interval until the main exposure in step S11. Predict.

  Once the in-focus position is calculated in step S19, in-focus driving is then performed (S21). Here, the lens control unit 103 and the motor driving unit 102 move the focus lens to the in-focus position predicted in step S19. When the reliability of the predicted position is low as a result of the final scan, the focus lens is moved to the final focus position (see S51, S57, and S59 in FIG. 5).

  In step S21, when the in-focus driving is performed, it is next determined whether or not the 2R holding is continued (S23). As described above, in the continuous shooting mode, continuous shooting is continued while the release button is fully pressed. In this step, it is determined whether or not the 2nd release (2R) switch that is linked to the full depression of the release button remains on.

  If 2R is held as a result of the determination in step S23, the process returns to step S11, the in-focus position is predicted, main exposure is performed, and continuous shooting is continued. On the other hand, if 2R holding has not been continued, that is, if the user's finger has moved away from the release button, the flow of continuous shooting AF ends.

  Next, detailed operation of the scan control in step S1 (see FIG. 2) and step S17 (see FIG. 3) will be described using the flowchart shown in FIG. In the scan control flow, first, scan driving is started (S31). Here, the main body control unit 204 instructs the lens control unit 103 to start scanning of the focus lens by the motor driving unit 102. When scanning is started, the contrast AF circuit in the main body control unit 204 calculates a contrast value based on the image signal from the image sensor 201.

  When the scan driving is started, next, the determination of the direction determination is awaited (S33). When scan driving is started, the contrast value is calculated as described above every time image data for one frame is output, so whether the contrast value increases or decreases for each frame. judge. When the contrast value increases or decreases by a predetermined number of frames, the direction determination is confirmed.

  If the direction determination is confirmed in step S33, it is next determined whether the result of the direction determination is a forward direction or a reverse direction (S35). If the contrast value has increased, the forward direction is determined because there is a peak in the direction in which the focus lens is moving. On the other hand, if the contrast value has decreased, the reverse direction is determined because there is a peak in the direction opposite to the direction in which the focus lens is moving.

  If the result of determination in step S <b> 35 is that the reverse direction is determined, then the scan direction is reversed (S <b> 37). Here, the main body control unit 204 instructs the lens control unit 103 to reverse the focus lens scanning direction by the motor driving unit 102.

  If the scan direction is reversed in step S37 or if the result of determination in step S35 is the forward direction, next peak detection is waited (S39). As described above, the contrast AF circuit calculates a contrast value every time image data for one frame is output during scan driving. This step waits for a change from an increase to a decrease in contrast value that occurs when the contrast value exceeds the peak.

  If the peak of the contrast value is detected in step S39, then the in-focus position is calculated and the in-focus history is stored (S41). Here, the focus evaluation position (focus lens position) of the peak of the AF evaluation value is calculated from the AF evaluation values (contrast value) at three points near the peak and the focus lens position at that time, using an approximate expression of a quadratic curve. ) Is calculated. The in-focus position and the in-focus time are stored in the storage unit 203 as an in-focus history as a set. The storage unit 203 functions as a time storage unit that detects and stores the time at which the focus lens position at which the contrast of the image reaches a peak is detected by executing a scanning operation.

  In step S41, when the in-focus position is calculated and the in-focus history is stored, it is next determined whether or not a 2nd release has been detected (S43). Here, as in step S3 (see FIG. 2), the determination is made based on the state of the 2nd release switch.

  If the result of determination in step S43 is that 2nd release has not been detected, the in-focus direction is determined (S45). In step S39, since the contrast value peak is exceeded, the driving direction of the focus lens is reversed in order to detect the peak again. Therefore, the main body control unit 204 instructs the lens control unit 103 to reverse the focus lens scanning direction by the motor driving unit 102.

  When the drive direction is reversed in step S45, the process returns to step S33, the peak of the contrast value is obtained in steps S33 to S41, and the in-focus position is calculated. On the other hand, if the result of determination in step S43 is that a 2nd release has been detected, the scan control flow is terminated and the original flow is restored. In the flow shown in FIG. 4, the 2nd release is detected in step S43. However, when the 2nd release is detected during the execution of steps S33 to S41, the scan control is terminated.

  Next, a detailed operation for calculating the in-focus position in step S19 (see FIG. 3) will be described using the flowchart shown in FIG. In the in-focus position calculation flow, first, the final in-focus position availability determination is performed (S51). As described above, in contrast AF, a contrast value is calculated every time one frame of image data is output from the image sensor 201. For example, in the case of 60 frames / second, the contrast value is calculated every 1/60 seconds. For this reason, depending on the timing at which the 2nd release switch is turned on and continuous shooting is started, a considerable amount of time has elapsed since the in-focus position (see step S41 in FIG. 4) has been calculated. If the subject moves abruptly after the focal position is calculated, the reliability of the in-focus position prediction calculation may be low. Therefore, in this step, the final in-focus position information (the in-focus position and the in-focus time, see the in-focus history in step S41 in FIG. 4) and the current information (the current position and the current time) are used. Is determined to be reliable or not. Detailed operation of the final focus position availability determination will be described later with reference to FIG.

  If it is determined in step S51 that the final focus position is usable, it is next determined whether or not the final focus position is usable (S53). Here, the determination is made according to the determination result in step S51.

  If the result of determination in step S51 is that the final focus position cannot be used, next, focus position estimation in the final scan is performed (S55). The result of the determination in step S53 is No when the in-focus position cannot be determined based on the obtained image data as a result of the final scan. Therefore, in this step, the focus position is estimated using the result of the last scan. Detailed operation of in-focus position estimation in this final scan will be described later with reference to FIGS.

  If the focus position is estimated in the last scan in step S55, it is next determined whether or not the focus position can be estimated (S57). In the estimation of the focus position in step S55, it is determined whether or not the focus position can be estimated (see S89 and S91 in FIG. 7). In step 57, the determination is made based on the determination result.

  If the result of determination in step S57 is that focus position estimation is not possible, focus position pos = current LDP is set (S59). Here, since the reliability of the in-focus position estimated in step 55 is low, the in-focus position pos determined in the final scan is set as the focus lens drive position (LDP) of the photographing lens 101. The in-focus drive when the in-focus position cannot be predicted will be described later with reference to FIG.

  On the other hand, if the final in-focus position is usable as a result of the determination in step S53, or if the in-focus position can be estimated as a result of the determination in step S57, the moving object predicted time is calculated (S61). ). Here, when the in-focus position is predicted using the in-focus history, the time until the main exposure is calculated. When the release button is fully pressed, the time from when the 2nd release switch is turned on until the main exposure is reached. When continuous shooting is in progress, the time is the time until the next main exposure. Note that the time until the main exposure is an intermediate point during the main exposure (when half of the time from the start of exposure to the end of exposure has elapsed).

  Once the moving body prediction time is calculated, a predicted pulse position calculation is performed, and this calculated value is set to pos (S63). Here, using the in-focus history, after the moving body prediction time calculated in step S61, the subject position is predicted and calculated, and driving for positioning the focus lens of the photographing lens 101 at the in-focus position of the prediction calculation result is performed. The pulse position LDP is set. In the present embodiment, the prediction calculation is performed by linear approximation using the least square method using the information on the in-focus position stored in the in-focus history, but it is of course possible to employ a different prediction calculation formula. Absent. In the present embodiment, the driving position of the focus lens is represented by LDP. That is, it is represented by the number of pulses from a reference position such as a photo interrupter.

  If the focus position pos = current LDP is set in step S59, or if a value is set in predicted pulse position calculation => pos in step S63, the process returns to the original flow.

  As described above, the focus position at a predetermined time is based on a plurality of past focus position information stored (see S41 in FIG. 4) in accordance with the detection result of the last scan operation (see S17 in FIG. 3). Is predicted (S53 Yes in FIG. 5), the in-focus position of the main photographing time by the image sensor is predicted based on the stored past position information (S63 in FIG. 5). The focus lens is moved using the result of the prediction calculation (see S21 in FIG. 3).

  In addition, a focus position at a predetermined time is predicted based on a plurality of stored past focus position information (see S41 in FIG. 4) in accordance with the detection result of the last scan operation (see S17 in FIG. 3). When it is determined not to be performed (No in S53 in FIG. 5), the position of the focus lens at the time of actual photographing is set as the position of the focus lens at the end of the last scan operation (S59 in FIG. 5).

  Next, detailed operation of the final focus position availability determination in step S51 (see FIG. 5) will be described using the flowchart shown in FIG. If the flow for determining whether or not the final focus position can be used is entered, it is first determined whether or not | current LDP−final focus position | ≧ TH1 (S71). Here, from the focus lens position (current LDP) at the time when the scanning operation is terminated immediately before the main exposure, the latest focus among the plurality of past focus position information stored in step S41 (see FIG. 4). It is determined whether or not the absolute value of the value obtained by subtracting the position information (final in-focus position) is greater than the first predetermined value (TH1). This | current LDP-final in-focus position | corresponds to the distance LA in FIG.

  If the result of determination in step S71 is No, it is next determined whether or not current time-final focusing time ≧ TH2 (S73). Here, a value obtained by subtracting the time at which the latest in-focus position information from among the plurality of past in-focus position information stored in step S41 is subtracted from the time at which the focus lens position is detected by the scan operation executed last. Then, it is determined whether or not it is larger than the second predetermined value (TH2). This “current time-final focusing time” corresponds to time TA in FIG. 9 described later.

  If the result of determination in step S73 is No, it is determined that the final focus position can be used (S75). On the other hand, if the result of determination in step S71 is Yes, or if the result of determination in step S73 is Yes, it is determined that the final focus position cannot be used (S77). When the determination is made in step S75 or S77, the process returns to the original flow.

  As described above, in the flow for determining whether or not the final focus position can be used, the difference between the latest position information of the plurality of stored past position information and the position of the focus lens detected by the last scan operation is the first. When it is larger than the predetermined value (TH1) of 1 (S71 Yes), it is determined that the in-focus position at the predetermined time is not predicted based on the past position information (S77). Further, there is a difference between the time when the latest position information among the plurality of past position information stored in the time storage unit (storage unit 203) is detected and the time when the focus lens position is detected by the last scan operation. When it is larger than the second predetermined value (S73 Yes), it is determined that the in-focus position at the predetermined time is not predicted based on the past position information (S77).

  Next, an example of prediction of the in-focus position during continuous AF will be described with reference to FIGS. 8 and 9. FIG. 8 shows the lens position control when the prediction can be performed, and FIG. 9 shows the lens position control when the prediction cannot be performed. 8 and 9, the horizontal axis indicates the change in time, and the vertical axis indicates the lens position.

  In FIG. 8, the first scan SC1 is performed between times T1 and T3, and during this time, the contrast value (AF evaluation value) is repeatedly calculated each time image data from the image sensor 201 is output. (See S33 to S39 in FIG. 4). At this time, when the peak of the contrast value is detected, the in-focus position is calculated. In the example shown in FIG. 8, the focus position z11 is calculated at time T2.

  When the first scan SC1 is completed, the driving direction of the focus lens is reversed (see S45 in FIG. 4), the second scan SC2 is executed from time T3 to T5, and the in-focus position z12 is calculated at time T4. Thereafter, similarly, the third scan SC3 is executed between times T5 and T7, the in-focus position z13 is calculated at time T6, and the fourth scan SC4 is executed between times T7 and T9. The focus position z14 is calculated at T8, the fourth scan SC5 is executed between times T9 and T11, the focus position z15 is calculated at time T10, and the sixth scan SC6 is performed between times T11 and T21. The focus position z16 is calculated at time T12.

  A line connecting the lens positions at the in-focus positions m1 to m6 becomes a subject movement line P indicating a change in the subject position. The focus position m6 indicates the latest focus position, the focus position m5 indicates the previous focus position, the focus position 4 indicates the previous focus position, and corresponds to these focus positions. The lens position (z11 to z16) to be used and the time (T2, T4, T6, T8, T10, T12) at that time are set and stored in the storage unit 203 as a focusing history.

  At time T21, when the scanning is finished by pressing down the 2nd release or when the timing of the next main exposure at the time of continuous shooting is reached, the final focus position availability determination in step S53 during the focus position calculation shown in FIG. 5 is performed. In the example shown in FIG. 8, it is determined that the final focus position (in this example, the focus position m6) can be used.

  When it is determined that the final in-focus position can be used, the main exposure starts at time T31, and the position of the subject at time T32 when ½ of the exposure time elapses is calculated as the moving object predicted time from time T21 to time T32. The focus position at the time of the main exposure is predicted and calculated based on the equation representing the moving object prediction time and the subject movement line P (see S63 in FIG. 5), and the focus lens is driven. This is performed along the drive line AFD (S21 in FIG. 3).

  FIG. 9 shows an example of control of the lens position when prediction cannot be performed as described above. From time T1 to time T11, scans SC1 to SC5 are performed as in the case of FIG. After starting the sixth scan SC6a, the scan direction is reversed at time T13. This is a case where the direction of the focus lens is reversed and the movement of the focus lens is started in step S45 (see FIG. 4). However, as a result of the determination and determination in steps S33 and S35, the contrast value has decreased and the scan direction is reversed. Yes (see S37 in FIG. 4).

  The scan direction is reversed, and at time T21 during execution of the scan SC6b, the 2nd release is pushed down or the timing of the main exposure next to the continuous shooting is reached. Also in this case, the final focus position availability determination in step S53 during calculation of the focus position shown in FIG. 5 is performed. In the example shown in FIG. 9, it is determined that the final focus position (in this example, the focus position m5) cannot be used. That is, the determination in step S71 is | current LDP−final in-focus position | ≧ TH1. In the example shown in FIG. 9, the difference LA between the final focus position m5 and the current LDP (z21) is larger than the predetermined value TH1. If the determination in step S73 is made, the difference time TA between the time T10 at the final focus position m5 and the current time T21 is greater than the predetermined value TH2.

  Thus, in the example shown in FIG. 9, it is determined that the final focus position (m5) cannot be used. For this reason, if the in-focus position can be estimated using the contrast value (AF evaluation value) in the final scan (the sixth scan SC6a, SC6b) (S57 in FIG. 5), the estimated in-focus position Is used to predict the in-focus position (S63 in FIG. 5), and the focus lens is driven along the drive line AFD (S21 in FIG. 4). On the other hand, if the focus position cannot be estimated, focus drive is performed at the lens position z21 corresponding to the current position at the current time T21 (S59 in FIG. 5).

  Next, the detailed operation of in-focus position estimation in the final scan in step S55 (see FIG. 5) will be described using the flowchart shown in FIG.

  If the in-focus position estimation flow in the final scan is entered, it is first determined whether or not the number of data is 5 or more (S81). In the calculation of the in-focus position in contrast AF, the peak position (in-focus position) is calculated using data of three points near the peak of the contrast value (S41 in FIG. 4). However, since the focus position estimation in the final scan is in a state where the peak of the contrast value is not detected, whether or not there is information on five or more points as the contrast value in order to ensure the reliability of the peak estimation. Judgment is made.

  If the result of determination in step S81 is that there are 5 or more data points, Gaussian function approximate expression calculation is performed (S83). Here, the peak position of the contrast information is calculated by the Gaussian function approximate expression using data of five points or more, and this peak position is set as the focus lens position (zc). Details of the calculation of the focus lens position (zc) by this Gaussian function approximate expression will be described later.

  Once the Gaussian function approximate expression is calculated in step S83, it is next determined whether or not the evaluation value difference ≧ TH3 (S85). When calculating the peak position of the contrast value with an approximate expression, the reliability is low in a portion where the difference in AF evaluation value (contrast value) is small, such as the base portion of a Gaussian function. Therefore, in this step, reliability is determined based on the difference in AF evaluation values. In the example shown in FIG. 10 described later, the difference between the AF evaluation values corresponds to the maximum and minimum difference Z of the five AF evaluation values.

  If the result of determination in step S85 is that the difference in AF evaluation values is greater than or equal to a predetermined value TH3, it is next determined whether or not there is reliability (S87). The calculation for determining the reliability will be described together with the detailed description of the calculation of the Gaussian function approximation formula. However, when approximating the Gaussian curve, the Gaussian curve and the rest of the actual data are approximated. The sum of squares of the differences (see formula (3) described later) is used as the basis for determining the reliability.

  If the result of determination in step S87 is OK, it is determined that the in-focus position can be estimated (S89). On the other hand, if the result of determination in step S87 is NG, or the result of determination in step S81 is that the number of data is less than 5, or the result of determination in step S85 is the difference in AF evaluation values Is smaller than TH3, it is determined that the in-focus position cannot be estimated (S91).

  If it is determined in steps S89 and S91 whether the in-focus position can be estimated, the process returns to the original flow and proceeds to the above-described step S57 (see FIG. 5).

  An example of in-focus position estimation in the final scan will be described with reference to FIG. FIG. 10 shows a change in contrast value (AF evaluation value) during scan control. The horizontal axis indicates the position of the focus lens, and the vertical axis indicates the AF evaluation value. In this example, when 5 points of contrast values (AF evaluation values) can be calculated for 5 frames of image data, a 2nd release or the like is entered, so the scanning operation is stopped, and contrast is obtained from the acquired 5 points. Estimate the peak position of the value.

  The first point is that the AF evaluation value is AFval_1 at the focus lens position z1 (this result is abbreviated as (AFval_1, z1)). Thereafter, the second point is (AFval_2, z2), the third point is (AFval_3, z3), the fourth point is (AFval_4, z4), and the fifth point is (AFval_5, z5). In the figure, the solid line shows a curve of contrast information obtained by connecting the actual measured values of contrast values (AF evaluation values) from the first point to the fifth point.

  In FIG. 10, a two-dot chain line is a contrast value curve estimated by the Gaussian function approximate expression in step 83 using the contrast values from the first point to the fifth point. The peak position zc can be estimated from the estimated contrast information curve G. A broken line indicates a contrast information curve R obtained when scanning is continued after the fifth point. Ideally, it is desirable that the estimated contrast information curve G and the contrast information curve R match.

  As described above, even when the position of the focus lens at which the contrast of the image reaches the peak cannot be detected by the last scan operation (No in S53 in FIG. 5), the position of the focus lens at which the peak is estimated is estimated. (S55 in FIG. 5 and S83 in FIG. 7). If the focus lens focus position can be estimated (S57 in FIG. 5), the focus position at a predetermined time is calculated based on both the estimated focus lens position and the stored past position information. (S61 in FIG. 5), the in-focus position at a predetermined time is predicted (S63 in FIG. 5).

  Next, the calculation method using the Gaussian function approximate expression in step S83 (see FIG. 7) will be described. When the AF evaluation value obtained during the peak detection operation of the focus lens is AFval_i and the corresponding focus lens position is zi, for a plurality of points (AFval_i, zi) (i = 1, 2, 3,..., N). Then, a process for obtaining a Gaussian curve passing through the nearest is performed.

This Gaussian curve can be expressed as the following equation (1).
AFval_i = Nexp {− (zi−zc) ² / 2σ ² } (1)
Here, N is a constant, zc is an average, and σ is variance.

Taking the logarithm of both sides of the Gaussian function of equation (1), the following equation is derived.
Ln (AFval_i) = lnN + {− (zi−zc) ² / 2σ ² } (2)

In the formula (2), ln (AFval_i) = Fi, the put and ^{a = -1 / 2σ 2, b} = 2zc / 2σ 2, c = lnN-zc 2 / 2σ 2, mere quadratic Gaussian curve "F = Az ² + bz + c ".

  The in-focus position can be calculated by substituting coefficients a and b into zc = −b / 2a. In the present embodiment, the coefficients a, b, and c are obtained by solving simultaneous equations obtained by setting each equation value obtained by partial differentiation of the residual square sum of the quadratic curve representing the Gaussian curve to 0.

The residual sum of squares S can be expressed as the following equation (3).
S = Σ (Fi−azi ² −bzi−c) ² (3)
As described above, the residual sum of squares is used for determination of reliability in step S87.

The result of partial differentiation of the above equation (3) with the coefficients a, b, and c is shown as the following equations (4), (5), and (6).
∂S / ∂a = Σ (−2 (Fi−azi ² −bzi −c)) zi ² (4)
∂S / ∂b = Σ (−2 (Fi−azi ² −bzi−c)) zi (5)
∂S / ∂c = Σ (−2 (Fi−azi ² −bzi −c)) (6)
Here, i = 1 to n.

In each equation (4), (5), (6), the partial differential value is 0.
Then, the following formulas (7), (8), and (9) are derived.
Σ (zi ² Fi) = aΣ (zi ⁴ ) + bΣ (zi ³ ) + cΣ (zi ² ) (7)
Σ (zi Fi) = aΣ (zi ³ ) + bΣ (zi ² ) + cΣ (zi) (8)
Σ (Fi) = aΣ (zi ² ) + bΣ (zi) + cn (9)

In the above equations (7), (8), (9), Σ (zi) = A, Σ (Fi) = B, Σ (ziFi) = C, Σ (zi ² ) = D, Σ (zi ³ ) = If E, Σ (zi ⁴ ) = F, and Σ (zi ² Fi) = G, they can be expressed as the following equations (10), (11), and (12).
G = aF + bE + cD (10)
C = aE + bD + cA (11)
B = aD + bA + cn (12)

Solving the simultaneous equations (10), (11), and (12) with respect to a, b, and c yields the following equations (13), (14), and (15).
a = ((AB-Cn) (D2-AE)-(DC-AG) (A2-Dn)) / ((AD-En) (D2-AE)-(DE-AF) (A2-Dn))). (13)
b = ((DC-AG) -a (DE-AF)) / (D2-AE)) (14)
c = (B−bA−aD) / n (15)

  The focus lens position (focus position) at which the AF evaluation value is maximum is represented by the average zc that is the median value of the Gaussian distribution. Therefore, a, b, and c are calculated to obtain zc = −b / 2a. it can.

  As described above, in one embodiment of the present invention, the scan lens is repeatedly executed to detect and store the position information of the focus lens at which the contrast of the image reaches a peak, and the plurality of stored past position information are stored. Based on the detection result of the last scan operation performed, the focus position at the predetermined time is predicted based on the plurality of past position information stored. It is determined whether or not the focal position is predicted (see S53 in FIG. 5). For this reason, it is possible to predict an appropriate in-focus position according to the state of the subject. That is, it is possible to appropriately predict the in-focus position even when the movement of the subject increases before the main exposure.

  In the embodiment of the present invention, the Gaussian function approximate expression is used for estimating the in-focus position in step S83 (see FIG. 7). However, the present invention is not limited to this, and an approximate expression for obtaining the peak position of the contrast value is used. Of course, a different function may be adopted.

  In the embodiment of the present invention, the digital camera is used as the photographing device. However, the camera may be a digital single lens reflex camera or a compact digital camera, such as a video camera or a movie camera. It may be a camera for moving images, or may be a camera built in a mobile phone, a smart phone, a personal digital assistant (PDA), a game machine, or the like. In any case, the present invention can be applied to any device that performs focus adjustment by contrast AF.

  In addition, regarding the operation flow in the claims, the specification, and the drawings, even if it is described using words expressing the order such as “first”, “next”, etc. It does not mean that it is essential to implement in this order.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, you may delete some components of all the components shown by embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 100 ... Interchangeable lens, 101 ... Shooting lens, 102 ... Motor drive part, 103 ... Lens control part, 104 ... Memory | storage part, 200 ... Camera body, 201 ... Imaging device 202 ... Liquid crystal display unit 203 ... Storage unit 204 ... Main body control unit 205 ... Operation unit

Claims (6)

In a focus adjustment apparatus that includes a focus lens that can be moved in the optical axis direction by a lens driving unit and that forms an image of light from a subject and performs focus adjustment of a photographing optical system.
An imaging device for obtaining imaging data of the subject imaged by the imaging optical system;
Control that moves the focus lens to execute an image pickup operation by the image pickup device, and performs a scan operation to detect the position of the focus lens at which an image contrast peak is based on a plurality of image pickup data output from the image pickup device. And
Comprising
The control unit
The scan operation is repeatedly executed until immediately before the main exposure to detect and store the position information of the focus lens at which the contrast of the image reaches a peak, and focus at a predetermined time based on the plurality of stored past position information. A prediction control unit for predicting a position;
A determination unit configured to determine whether or not to predict an in-focus position at a predetermined time based on the plurality of stored past position information according to a detection result of a scan operation performed immediately before the main exposure;
A focus adjustment device comprising:   The determination unit determines whether a difference between the latest position information of the stored past position information and the position of the focus lens at the time when the scanning operation is ended immediately before the main exposure is a first predetermined value. 2. The focus adjustment apparatus according to claim 1, wherein when the value is larger than the value, it is determined that the in-focus position at a predetermined time is not predicted based on the past position information. A time storage unit that detects and stores a time at which the focus lens position at which the contrast of the image reaches a peak is detected by executing the scanning operation
The determination unit is configured such that a difference between a time when the latest position information among a plurality of past position information stored in the time storage unit is detected and a time when the scanning operation is ended immediately before the main exposure is determined. When it is larger than the second predetermined value, it is determined that the in-focus position at the predetermined time is not predicted based on the past position information.
The focus adjusting apparatus according to claim 1, wherein: The control unit controls the main exposure operation by the image sensor,
When the determination unit predicts an in-focus position at a predetermined time based on the stored plurality of past position information according to the detection result of the scanning operation performed immediately before the main exposure,
The prediction control unit moves the focus lens by predicting a focus position at the main exposure time by the imaging element based on the stored plurality of past position information.
The focus adjusting apparatus according to claim 1, wherein: When the determination unit determines not to predict the in-focus position at a predetermined time based on the stored plurality of past position information according to the detection result of the scan operation performed immediately before the main exposure,
The control unit sets the position of the focus lens at the time of the main exposure as the position of the focus lens at the end of the scanning operation performed immediately before the main exposure.
The focus adjusting apparatus according to claim 1, wherein: In a focus adjustment device that performs focus adjustment of a photographing optical system that includes a focus lens that can be moved in the optical axis direction by a lens driving unit and forms an image of light from a subject.
An imaging device for obtaining imaging data of the subject imaged by the imaging optical system;
Control that moves the focus lens to execute an image pickup operation by the image pickup device, and performs a scan operation to detect the position of the focus lens at which an image contrast peak is based on a plurality of image pickup data output from the image pickup device. And
Comprising
The control unit
The scan operation is repeatedly executed until immediately before the main exposure to detect and store the position information of the focus lens at which the contrast of the image reaches a peak, and focus at a predetermined time based on the plurality of stored past position information. A prediction control unit for predicting a position;
A peak estimator that estimates the position of the focus lens that becomes the peak even if the position of the focus lens that makes the contrast of the image peak cannot be detected by the scanning operation performed immediately before the main exposure;
Have
The prediction control unit includes a focus lens position that is a peak estimated by the peak estimation unit, or the stored past position information, or a focus lens position that is a peak estimated by the peak estimation unit and the stored past position. Calculate a predetermined time focus position based on both information,
A focusing device characterized by that.