JP2013020123A - Focus adjustment device and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus adjustment device capable of reducing an arithmetic load when detecting a focus.SOLUTION: The focus adjustment device includes: focus detection means for detecting a focus adjustment state at a first time and at a second time; selection means for selecting an attention focus area to be focused from a plurality of focus areas on the basis of the focus adjustment state detected by the focus detection means at the first time; focus adjustment means for adjusting the focus adjustment state on the basis of the focus adjustment state of the attention focus area detected by the focus detection means at the first time; and composition change determination means for comparing a plurality of focus adjustment states detected at the first time by the focus detection means with a plurality of focus adjustment states detected at the second time by the focus detection means, to determine whether or not a composition change occurs. When it is determined that the composition change does not occur, the focus adjustment means adjusts the focus adjustment state on the basis of the focus adjustment state at the second time of the attention focus area selected at the first time.

Description

  The present invention relates to a focus adjustment device and a camera.

  In automatic focus adjustment of a camera, a plurality of focus areas for performing distance measurement (focus detection) are generally prepared. In such automatic focus adjustment using a plurality of focus areas, a technique is known in which a camera automatically determines a ranging position from a plurality of focus areas. For example, Patent Document 1 describes an imaging apparatus that recognizes a scene change (composition change) from the previous focus adjustment by using changes in the contrast, luminance, and hue of the subject during focus adjustment.

JP 2009-265138 A

  The imaging device described in Patent Document 1 has a problem that the calculation load at the time of focus detection is large because a scene change is detected from an image signal generated by the imaging element.

The invention according to claim 1 is a focus adjustment device that adjusts a focus adjustment state, wherein a focus adjustment state corresponding to each of a plurality of focus areas is obtained at a first time and a second time after the first time. Focus detection means for detecting, selection means for selecting a focus area to be focused from a plurality of focus areas based on the focus adjustment state detected by the focus detection means at the first time, and focus detection at the first time Based on the focus adjustment state corresponding to the focus area of interest detected by the means, the focus adjustment means for adjusting the focus adjustment state, the plurality of focus adjustment states detected at the first time by the focus detection means, and the focus detection means A composition change determining means for comparing the plurality of focus adjustment states detected at the second time and determining whether or not a composition change has occurred. The means determines the focus adjustment state based on the focus adjustment state at the second time of the focus area selected by the selection unit at the first time when the composition change determination unit determines that the composition change has not occurred. A focus adjusting device characterized by adjusting.
A tenth aspect of the present invention is a camera comprising the focus adjustment device according to any one of the first to ninth aspects.

  According to the present invention, it is possible to reduce the calculation load during focus detection.

It is a block diagram which shows the structure of the digital camera which concerns on the 1st Embodiment of this invention. 6 is a schematic diagram showing a focus area of the focus adjustment apparatus 400. FIG. 10 is a flowchart of processing executed by the focus adjustment device 400 when the release button is half-pressed in the automatic selection AF mode. 10 is a flowchart of processing executed by the focus adjustment device 400 when the release button is pressed halfway again in the automatic selection AF mode. It is a figure for demonstrating the defocus difference calculation process performed by step S209 of FIG. It is a flowchart of a defocus difference calculation process called in step S209 of FIG.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of a digital camera according to the first embodiment of the present invention. The digital camera 100 includes a camera body 200 and an interchangeable lens 300 that can be attached to and detached from the camera body 200.

  The interchangeable lens 300 includes a lens optical system 1 that receives a light beam from a subject and forms a subject image on an imaging surface. The lens optical system 1 includes a focus adjustment lens that can move in the optical axis direction. The camera body 200 includes an imaging element 6 that captures a subject image formed by the lens optical system 1, converts the subject image into an electrical signal, and outputs the electrical signal. The image sensor 6 is a solid-state image sensor such as a CCD or CMOS. Although omitted in FIG. 1, an infrared cut filter for cutting infrared light, an optical low-pass filter for preventing image aliasing noise, and the like are arranged on the imaging surface of the image sensor 6. .

  On the optical path of the light beam that has passed through the lens optical system 1 in the camera body 200, the quick return mirror 2 is disposed so as to block the image sensor 6. The quick return mirror 2 is in the position shown in FIG. 1 before exposure, and reflects the light beam from the lens optical system 1 toward the viewfinder screen 3 disposed on the upper part of the camera body 200. The viewfinder screen 3 is disposed at a position conjugate with the image pickup device 6 with respect to the quick return mirror 2.

  The light beam reflected by the reflection surface of the quick return mirror 2 passes through the finder screen 3 and is introduced into the pentaprism 4 and enters the eyepiece lens 5. Therefore, the photographer can visually recognize the subject image through the eyepiece 5 in the state before exposure. A part of the light beam introduced into the pentaprism 4 enters the photometric sensor 16 through the photometric lens 15. The photometric sensor 16 measures the amount of light of the subject light and outputs an electrical signal corresponding to the amount of light.

  A liquid crystal panel 18 is provided between the finder screen 3 and the pentaprism 4. The liquid crystal panel 18 is provided with display segments corresponding to each of a plurality of focus areas described later. Each of these segments is configured to be able to control whether light is transmitted or blocked depending on whether a voltage is applied. Note that the portion of the entire liquid crystal panel 18 where the display segment is not provided always transmits light. Accordingly, when the photographer visually recognizes the subject image via the eyepiece 5, the display segment controlled to block the light is superimposed on the subject image and displayed on the viewfinder.

  Near the center of the quick return mirror 2 (near the optical axis of the lens optical system 1) is a half mirror, and part of the subject light passes through this half mirror. This transmitted light beam is reflected by the sub mirror 7 provided on the back surface of the quick return mirror 2 and is incident on a phase difference AF detection element 8 in a focus detection device 400 described later.

  At the time of exposure, the quick return mirror 2 and the sub mirror 7 are driven by a motor (not shown) and move to the lower part (retracted position) of the finder screen 3. When the quick return mirror 2 and the sub mirror 7 are moved to the retracted position, the light beam transmitted through the lens optical system 1 is introduced into the image sensor 6, and at this time, the image sensor 6 captures a subject image.

  The camera body 200 includes a focus adjustment device 400 that adjusts the focus adjustment state of the subject image formed by the lens optical system 1. The focus adjustment apparatus 400 includes a phase difference AF detection element 8, an AF-CCD control unit 9, a defocus calculation unit 10, a focus area position determination unit 11, and a lens drive amount calculation unit 12. Hereinafter, each of these units will be described in order.

  The phase difference AF detection element 8 includes a plurality of charge accumulation type line sensors such as a CCD. Two of these line sensors form a pair, and the reflected light of the sub-mirror 7 is divided into two by a mask (not shown) and then re-imaged on the pair of line sensors. These line sensors are arranged so that a plurality of focus areas described later are formed on the photographing screen.

  The phase difference AF detection element 8 is connected to an AF-CCD control unit 9 that controls an appropriate gain and accumulation time of the line sensor. The AF-CCD control unit 9 reads out the electric charge accumulated in the line sensor as necessary, and outputs an electric signal corresponding to the amount. The defocus calculation unit 10 calculates a defocus amount corresponding to each of a plurality of focus areas described later from the electrical signal output from the AF-CCD control unit 9. The defocus amount is an amount representing the amount of focus shift. Therefore, the calculation of the defocus amount means detection of the focus adjustment state of the subject image.

  The focus area position determination unit 11 selects a focus area to be focused based on the defocus amount calculated by the defocus calculation unit 10. In the following description, the focus area selected by the focus area position determination unit 11 is referred to as a focused focus area.

  The lens drive amount calculation unit 12 calculates a lens target position that is a target of the focus adjustment lens drive position based on the defocus amount corresponding to the focus area of interest calculated by the defocus calculation unit 10. Note that the lens target position here is a position where the defocus amount corresponding to the focus area is zero when the focus adjustment lens is driven to that position, that is, the subject image is focused in the focus area. Position.

  The lens drive control unit 13 adjusts the focus adjustment state of the subject image by driving the focus adjustment lens to the lens target position calculated by the lens drive amount calculation unit 12. In the interchangeable lens 300, a lens control motor 14, which is an actuator for driving the focus adjustment lens in the optical axis direction, is provided. The lens drive control unit 13 transmits the focus adjustment lens drive instruction to the lens control motor 14 via the electrical communication contact existing between the camera body 200 and the interchangeable lens 300, thereby adjusting the focus of the subject image. Adjust the condition.

  Each unit of the focus adjustment device 400 described above may or may not be configured by an independent member, circuit, or the like. For example, the defocus calculation unit 10 and the focus area position determination unit 11 may be included in the same circuit. Each of these units may be realized by a predetermined control program executed by the microprocessor.

  The camera body 200 includes a control circuit 17 in addition to the components described above. The control circuit 17 includes a microprocessor, a memory, and its peripheral circuits, and controls the entire digital camera 100. The control circuit 17 is connected to an operation member (not shown) for setting each photographing condition such as a focus area selection switch and a focus mode selection switch.

(Explanation of focus mode)
FIG. 2 is a schematic diagram showing a focus area of the focus adjustment apparatus 400. A total of 51 focus areas 21 are provided on the display screen 20 as shown in FIG. The liquid crystal panel 18 is provided with 51 display segments so as to correspond to the 51 focus areas 21.

  The digital camera 100 has a plurality of focus modes such as a manual focus mode, a single AF mode, and an automatic selection AF mode. When the photographer operates an operation member (not shown) (for example, a focus mode selection switch), the control circuit 17 selects a focus mode corresponding to the operation.

  The manual focus mode is a focus mode in which automatic focus adjustment is not performed. When this focus mode is selected, the lens driving motor 14 does not operate, and the photographer needs to manually adjust the focus using an operation member such as a focus ring (not shown). That is, in the manual focus mode, even when the photographer presses a release button (not shown) halfway, the digital camera 100 does not perform an operation related to focusing. When the photographer fully presses a release button (not shown), the control circuit 17 retracts the quick return mirror 2 and the sub mirror 7 from the optical path, and causes the image sensor 6 to capture the subject image.

  The single AF mode is a mode in which focus adjustment is performed on a focus area preselected by the photographer. The photographer selects any one focus area from the plurality of focus areas shown in FIG. 2 using an operation member (not shown) (for example, a focus area selection switch). When the photographer presses a release button (not shown) halfway, the control circuit 17 causes the focus adjustment device 400 to perform automatic focus adjustment. The focus adjustment device 400 adjusts the focus of the lens optical system 1 so that the subject image is focused in the focus area selected by the photographer. Further, the focus adjustment device 400 causes the liquid crystal panel 18 to display a focus area in which the defocus amount is less than a predetermined threshold, that is, a focus area that is in focus. Thus, the photographer can visually recognize the focused focus area with the finder. When the photographer fully presses a release button (not shown), the control circuit 17 causes the image sensor 6 to capture a subject image as in the manual focus mode.

  The automatic selection AF mode is a focus mode in which the focus adjustment device 400 performs processing to be described later and automatically selects a focus area to be a focus adjustment target. When the photographer presses a release button (not shown) halfway, the control circuit 17 causes the focus adjustment device 400 to execute processing to be described later. Hereinafter, processing executed by the focus adjustment apparatus 400 in the automatic selection AF mode will be described.

(Description of automatic selection AF mode)
FIG. 3 is a flowchart of processing executed by the focus adjustment device 400 when the release button is half-pressed in the automatic selection AF mode. When the photographer sets the automatic selection AF mode and presses the release button halfway, the processing shown in FIG. First, in step S102, the AF-CCD control unit 9 causes all line sensors included in the phase difference AF detection element 8 to accumulate charges. In step S103, the AF-CCD control unit 9 reads the electric charge of the line sensor that has performed the accumulation control, and outputs an electrical signal corresponding to the amount.

  In step S104, the defocus calculation unit 10 calculates a defocus amount corresponding to each of the plurality of focus areas based on the electrical signal output from the AF-CCD control unit 9 in step S103. In step S106, the focus area position determination unit 11 sorts the focus areas for which the defocus amounts have been calculated in step S104, in ascending order based on the defocus amounts. In the processing after step S106, a reliable defocus amount could not be calculated in step S104 (the reliability parameter was less than a predetermined amount), that is, the focus adjustment state could not be detected. Focus area is excluded.

  In step S107, the focus area position determination unit 11 converts the plurality of focus areas sorted in step S106 into a plurality of groups including focus areas having values close to the calculated defocus amount (ie, close focus adjustment states). Classify. This classification is performed as follows, for example.

  First, for the defocus amounts D1, D2,..., DN of the N focus areas sorted in step S106, the average value is Dave, and the variance v is obtained by the following equation (1).

  Next, a standard deviation σ is obtained by the following equation (2) as an amount representing the degree of variation in the defocus amounts D1, D2,.

  Finally, the defocus width H for classification into groups is determined by the following equation (3) using the standard deviation σ obtained by the above equation (2).

H = α · σ (3)
In the above equation (3), α is a coefficient, and usually about 0.4 to 0.6 is appropriate. The focus area position determination unit 11 sets a plurality of group areas by setting each focus area sorted in the closest order to a group boundary where a defocus amount difference between adjacent focus areas is equal to or greater than the defocus width H. Classify into:

  In step S <b> 108, the focus area position determination unit 11 selects a group that is considered to have an optimum subject for focusing from the plurality of groups classified in step S <b> 107. The “group considered to have the best subject for focusing” may be, for example, a group that includes a focus area that is closest to the sort order, or a focus area that is centered in the sort order. It may be a group included. Moreover, groups other than these may be sufficient.

  In step S109, the focus area position determination unit 11 selects a focus area to be focused from the focus areas included in the group selected in step S108. For example, the focus area with the closest defocus amount may be selected as the focus area.

  In step S111, the lens drive amount calculation unit 12 calculates the drive amount of the focus adjustment lens based on the defocus amount calculated in the focus area of interest. In step S112, the lens drive controller 13 causes the lens drive motor 14 to drive the focus adjustment lens to the lens target position based on the drive amount of the focus adjustment lens calculated in step S111, and performs focus adjustment. Thereafter, the focus adjustment device 400 causes the liquid crystal panel 18 to display all focus areas whose defocus amount is less than a predetermined threshold value.

  The focus adjustment apparatus 400 performs the processing of FIG. 3, the focus area selected in step S <b> 109, the group including the focus area (that is, all focus areas included in the group), and these The defocus amount calculated in the focus area and the focus area displayed on the liquid crystal panel 18 are stored in a storage device (not shown). These data stored in the storage device are updated and stored every time the processing of FIG. 3 is executed. Hereinafter, a group including the focused area of focus is referred to as a focused group.

  Note that the focus area of interest may not be determined by the processing in steps S106 to S109. For example, when the focus adjustment state cannot be detected for all the focus areas in step S104, the focus area position determination unit 11 cannot determine the focus area. In such a case, the lens drive control unit 13 performs a so-called scanning operation for driving the focus adjustment lens between the close end and the infinity end, and searches for a focus detection position.

  FIG. 4 is a flowchart of processing executed by the focus adjustment device 400 when the release button is pressed halfway again after the processing shown in FIG. 3 is executed in the automatic selection AF mode. Once the release button is pressed halfway and then the release button is pressed halfway again, the focus detection device 400 executes the process shown in FIG. 4 instead of the process shown in FIG. In this process, it is determined whether or not a composition change has occurred by the focus area position determination unit 11. If it is determined that no composition change has occurred, focus adjustment different from that in FIG. 3 is performed. On the other hand, when it is determined that a composition change has occurred, the same focus adjustment as in FIG. 3 is performed.

  Note that the predetermined time is between the time when the release button was pressed halfway last time and the processing shown in FIG. 3 was executed (the time when the defocus amount was calculated by the defocus calculation unit 10) and the time when the half-press was again pressed halfway. If (for example, 3 seconds) has elapsed, the focus detection apparatus 400 does not execute the process shown in FIG. 4 even if it is half-pressed again, and instead executes the process shown in FIG. This is because there is a high possibility that the subject has changed (that is, a composition change has occurred) if a sufficient amount of time has passed since the half-press was once made. That is, the focus area position determination unit 11 determines that a composition change has occurred when a predetermined time (for example, 3 seconds) has elapsed.

  Further, once the release button is pressed halfway (that is, when the process of FIG. 3 is executed), the AF-CCD control unit 9 detects the phase difference AF until the execution of the process of FIG. 4 is started. The accumulation control of the line sensor included in the element 8 is repeatedly performed every predetermined period. The AF-CCD control unit 9 executes AGC (auto gain control) of the line sensor based on the previous accumulation result every time this accumulation control is performed. If the subject light changes greatly at this time, for example, the previous time does not saturate. The brightness value of the sensor may be saturated (overflow) this time. Thus, when the presence or absence of saturation of the luminance value of any sensor is different between the previous time and the current time, the AF-CCD control unit 9 determines that the AGC has failed. Once it is determined that AGC has failed, the focus detection apparatus 400 executes the process of FIG. 3 instead of the process of FIG. 4 when the release button is pressed halfway next time. This is because the AGC failure is considered to be caused by a large luminance change of the photographing screen, and such a luminance change is considered to be caused by a composition change.

  First, in step S205, the AF-CCD control unit 9 reads the result of the last line sensor accumulation control and outputs an electrical signal. In step S206, the defocus calculation unit 10 defocuses corresponding to each focus area included in the group of interest stored in the execution of the process of FIG. 3 based on the electrical signal output from the AF-CCD control unit 9 in step S205. Calculate the focus amount. For example, if the focus group includes only four focus areas, the defocus amount is calculated not for all 51 points but only for these four focus areas.

  In step S208, it is determined whether or not there is no focus area in which the focus adjustment state can be detected in the focus area for which the defocus amount is calculated in step S206. That is, it is determined whether or not the focus adjustment state is undetectable for all the focus areas that are targets for calculating the defocus amount in step S206. If the focus adjustment state cannot be detected for any focus area, the process of FIG. 4 is stopped and the process of FIG. 3 is started from step S103. That is, the same processing as the first half-press is executed.

  In step S209, a defocus (Df) difference calculation process to be described later is executed. In this defocus difference calculation process, the defocus amount calculated in the previous process is compared with the defocus amount calculated this time for each focus area for which the defocus amount has been calculated in step S206, and the focus is calculated. A numerical value representing the uniformity of the change in the focus adjustment state in the area is calculated. Based on this numerical value, it is determined whether or not a composition change has occurred.

  In step S210, the focus area position determination unit 11 determines whether it is determined in step S209 that a composition change has occurred. If it is determined that a composition change has occurred, the processing of FIG. 4 is stopped, and the processing of FIG. 3 is started from step S103. That is, the same processing as the first half-press is executed. On the other hand, if it is determined that no composition change has occurred, the process proceeds to step S211.

  In step S211, the focus area position determination unit 11 determines whether or not the previous focus adjustment state of the focus area of interest can be detected in step S206. When the focus adjustment state of the previous focus area can be detected in the current process, the process proceeds to step S212, and the focus area position determination unit 11 selects the focus area selected as the previous focus area as the focus area. Choose as. On the other hand, if the focus adjustment state of the previous focus area of interest cannot be detected, the process proceeds to step S213. In step S213, the focus area position determination unit 11 selects, from the previous attention group, the focus area that is closest to the previous attention focus area as a new attention focus area.

  In step S214, the lens drive amount calculation unit 12 calculates the drive amount of the focus adjustment lens based on the defocus amount calculated in the focus area of interest. In step S215, the lens drive control unit 13 causes the lens drive motor 14 to drive the focus adjustment lens to the lens target position based on the drive amount of the focus adjustment lens calculated in step S214, and performs focus adjustment. In step S216, the focus detection apparatus 400 performs the same display on the liquid crystal panel 18 as when the processing of FIG. That is, the focus area in which the defocus amount is less than the predetermined threshold when the processing of FIG. 3 is executed is also displayed on the liquid crystal panel 18 this time.

  Note that the focus adjustment apparatus 400 performs the processing of FIG. 4, and similarly to the case of FIG. 3, the focus adjustment area, the focus group (that is, all focus areas included in the focus group), and these focus areas The calculated defocus amount and the focus area displayed on the liquid crystal panel 18 are stored in a storage device (not shown). These data stored in the storage device are updated and stored every time the process of FIG. 4 is executed.

  FIG. 5 is a diagram for explaining the defocus difference calculation process executed in step S209 of FIG. Now, it is assumed that the attention focus area 22 and the attention group 23 are selected from the 51 focus areas 21 included in the shooting screen 20 as shown in FIG. An example of the defocus amount in each focus area is shown in FIG. The left side of FIG. 5B shows the defocus amount of each focus area at the time of previous focusing, and the right side of FIG. 5B shows each focus at the current distance measurement. This is the defocus amount of the area.

  In the example shown in FIG. 5B, the defocus amount of the focus area 22 of interest, which was 0 at the previous focusing, is changed to 30 at the current distance measurement. In the case of hand-held shooting where the digital camera 100 is not fixed to a tripod or the like, or when shooting in a dark place and a high gain needs to be set, a condition in which the variation in the defocus amount tends to be large is shown in FIG. As shown in b), the defocus amount at the time of the current distance measurement may deviate from the vicinity of 0. Therefore, it is desirable to determine the composition change based on the relative change amount of the defocus amount distribution in a plurality of focus areas, not the change in the defocus amount in one focus area.

  In the present embodiment, in the defocus difference calculation process, the difference in the defocus amount between the current focus measurement and the previous focus in the focus area of interest is calculated as the defocus amount at the current distance measurement of each focus area included in the target group. By subtracting from, the difference in defocus amount is offset. For example, in FIG. 5B, the defocus amount of the focus area of interest at the time of current distance measurement is 30 and 0 at the previous focus. Therefore, after subtracting 30 from the defocus amount at the current distance measurement of each focus area included in the target group, a numerical value representing the uniformity of the focus adjustment state in the focus area is calculated.

  FIG. 6 is a flowchart of the defocus difference calculation process called in step S209 of FIG. First, in step S301, the focus area position determination unit 11 sorts all the focus areas included in the group of interest in the closest order based on the corrected defocus amount corresponding to the focus area. Here, the post-correction defocus amount refers to the defocus amount after the defocus amount offset described in FIG. 5 is applied to the defocus amount calculated in step S206 of FIG. Note that focus areas for which the defocus amount could not be calculated in step S206 (the focus adjustment state could not be detected) are excluded from the sorting process.

  In step S302, the focus area position determination unit 11 has a portion where the absolute value of the difference in the defocus amount after correction exceeds the defocus width H determined in step S107 in FIG. 3 for two focus areas adjacent in the sort order. It is determined whether or not. If the difference in the defocus amount after correction between two adjacent focus areas does not exceed the defocus width H, the process proceeds to step S304. On the other hand, if there is a combination of focus areas that exceeds the defocus width H, the process proceeds to step S307.

  In step S307, the focus area position determination unit 11 selects the focus area on the infinity side in the sort order, and the focus on the infinity side from the focus area, out of the two focus areas determined to exceed the defocus width H in step S302. All areas are set as exclusion focus areas. In step S308, the focus area position determination unit 11 determines whether or not there are a predetermined number of excluded focus areas (for example, 30% of the total number of focus areas included in the target group). If there is a predetermined number or more, an affirmative determination is made, and the process proceeds to step S309. In step S309, the focus area position determination unit 11 determines that no composition change has occurred, and ends the process of FIG. On the other hand, if the number of excluded focus areas is less than the predetermined number in step S309, the process proceeds to step S304.

  In step S304, the focus area position determination unit 11 calculates an average defocus amount Dfave for the corrected defocus amount of each focus area in the target group. In step S305, the focus area position determination unit 11 determines whether the average defocus amount Dfave is equal to or greater than a predetermined threshold value Dfsth. If the average defocus amount Dfav is greater than or equal to the threshold value Dfsth, an affirmative determination is made, and the process proceeds to step S306. In step S306, the focus area position determination unit 11 determines that a composition change has occurred. On the other hand, if a negative determination is made in step S305, the process proceeds to step S309. In step S309, the focus area position determination unit 11 determines that no composition change has occurred.

According to the digital camera according to the first embodiment described above, the following operational effects can be obtained.
(1) The focus area position determination unit 11 compares the plurality of defocus amounts detected at the previous half-press with the plurality of defocus amounts calculated at the half-press again, and has the composition changed? Determine whether or not. When it is determined by the focus area position determination unit 11 that no composition change has occurred, the lens drive control unit 13 re-executes the focus area selected by the focus area position determination unit 11 at the previous half-press time. The focus adjustment state is adjusted based on the defocus amount when half-pressed. Since it did in this way, the calculation load at the time of focus detection can be reduced.

(2) When the focus area position determination unit 11 determines that a composition change has occurred, the focus area position determination unit 11 selects a focus area based on the defocus amount calculated when the half-press is performed again. When the focus area position determination unit 11 determines that the composition change has occurred, the lens drive control unit 13 calculates the lens drive amount calculated based on the defocus amount of the focus area selected at the time of half-pressing again. To adjust the focus adjustment state. Since it did in this way, it becomes possible to select an appropriate focus area from the whole screen at the time of composition change.

(3) The focus area position determination unit 11 classifies the plurality of focus areas into a plurality of groups including focus areas having close defocus amounts based on the defocus amounts calculated at the previous half-press. The focus area position determination unit 11 includes a defocus amount calculated at the previous half-press for each focus area in the group classified at the previous half-press including the focus area selected at the previous half-press. And the defocus amount calculated at the time of half-press again, and the composition change is performed by calculating the uniformity of the defocus amount change in the focus area (that is, the degree of variation in the defocus amount change). Whether or not has occurred is determined. Since it did in this way, the composition change which recognized the subject as strange can be recognized.

(4) The defocus calculation unit 10 includes the focused focus area selected at the previous half-press, not all of the plurality of focus areas at the time of the half-press again, and the group classified at the previous half-press The defocus amount is calculated only for each focus area. Since it did in this way, it becomes possible to shorten the time which the calculation of a defocus amount requires.

(5) The lens drive control unit 13 determines that the composition change has not occurred by the focus area position determination unit 11 and the attention selected when the defocus calculation unit 10 is half-pressed again in the previous half-press. If the defocus amount of the focus area cannot be calculated (for example, due to saturation of luminance value or lack of contrast), the focus area selected at the previous half press will be included and the last half press The focus adjustment state is adjusted based on the defocus amount corresponding to one of the focus areas other than the focus area of interest among the focus areas in the group classified at times. Since it did in this way, even if it is a case where a focus focus area cannot detect a focus, it becomes possible to adjust a focus rapidly based on a suitable focus area.

(6) The focus area position determination unit 11 determines that a composition change has occurred when a predetermined time or more has passed after the release button was pressed halfway before the release button was pressed halfway again. Since it did in this way, when a composition change is anticipated reliably, it is not necessary to perform an extra calculation.

(7) The defocus calculation unit 10 calculates the defocus amount based on the luminance value of the light beam from the subject detected by the line sensor of the phase difference AF detection element 8. The focus area position determination unit 11 has a luminance value detected by the line sensor of the phase difference AF detection element 8 at the previous half-press time within a predetermined range, and the luminance value previously detected at the second half-press time. Is not within the predetermined range, it is determined that a composition change has occurred. Since it did in this way, when a composition change is anticipated reliably, it is not necessary to perform an extra calculation.

(8) The focus area where the defocus amount calculated by the defocus calculation unit 10 is in focus is displayed on the liquid crystal panel 18. When the focus area position determination unit 11 determines that the composition has not changed, the liquid crystal panel 18 displays the focus area that was in focus when the previous half-press was performed. Since this is done, it is possible to reduce variations in the display of the focus area (a state in which the displayed focus areas change one after another within a very short time), and to perform a display that is comfortable for the photographer.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

(Modification 1)
The offset of the defocus amount described in FIG. 5 can be performed based on a difference other than the difference in the defocus amount between the current focus measurement and the previous focus in the focus area of interest. For example, the defocus amount may be offset by taking the difference in the defocus amount between the current distance measurement and the previous focus for each focus area.

(Modification 2)
In the embodiment described above, the lens driving motor 14 exists in the interchangeable lens 300, but the lens driving motor 14 may exist in the camera body 200. In this case, the camera body 200 and the interchangeable lens 300 may be configured so that the driving force by the lens driving motor 14 in the camera body 200 is transmitted to the focus adjustment lens via a predetermined power transmission mechanism. The lens driving motor 14 may or may not be included in the focus adjustment device 400.

(Modification 3)
In the processing of FIG. 5, each focus area included in the target group is a processing target. This may also be processed for other focus areas. For example, among the focus areas located around the focus area of interest, a focus area in which a defocus amount close to the defocus amount of the focus area of interest is calculated may be a processing target of the processing in FIG. Alternatively, the process of FIG. 5 may be applied to all the focus areas shown in FIG. When the number of focus areas to be processed in FIG. 5 is increased, the storage capacity required for the storage device increases, but the number of focus areas for viewing the relative change amount of the defocus amount distribution increases, and the detection accuracy increases accordingly. .

(Modification 4)
In the embodiment described above, the uniformity of the change in the focus adjustment state in the focus area within the group of interest is calculated by offsetting the defocus amount. The present invention is not limited to such an embodiment. For example, the uniformity of the change in the focus adjustment state may be expressed by the average value of the defocus amount (that is, the uniformity of the change in the focus adjustment state is calculated by calculating the average value of the defocus amount). May be considered).

  As long as the characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 ... Lens optical system, 6 ... Imaging device, 8 ... Phase difference AF detection element, 9 ... AF-CCD control part, 10 ... Defocus calculating part, 11 ... Focus area position determination part, 12 ... Lens drive amount calculating part, 13 ... Lens drive control unit, 100 ... Digital camera, 200 ... Camera body, 300 ... Interchangeable lens

Claims (10)

A focus adjustment device for adjusting a focus adjustment state,
Focus detection means for detecting the focus adjustment state corresponding to each of a plurality of focus areas at a first time and a second time after the first time;
Selection means for selecting a focus area to be focused from the plurality of focus areas based on the focus adjustment state detected by the focus detection means at the first time;
Focus adjusting means for adjusting the focus adjustment state based on the focus adjustment state corresponding to the focus area of interest detected by the focus detection means at the first time;
Whether a composition change has occurred by comparing the plurality of focus adjustment states detected at the first time by the focus detection means with the plurality of focus adjustment states detected at the second time by the focus detection means. Composition change determination means for determining whether or not
With
The focus adjustment unit adjusts the focus at the second time of the focus area selected by the selection unit at the first time when the composition change determination unit determines that the composition change has not occurred. A focus adjustment device that adjusts the focus adjustment state based on a state. The focus adjustment apparatus according to claim 1,
The selection means selects the focus area of interest based on the focus adjustment state detected by the focus detection means at the second time when the composition change determination means determines that a composition change has occurred,
The focus adjustment unit is configured to select the focus based on the focus adjustment state of the focus area of interest selected by the selection unit at the second time when the composition change determination unit determines that the composition change has occurred. A focus adjustment device for adjusting an adjustment state. The focusing apparatus according to claim 1 or 2,
Based on the focus adjustment state detected by the focus detection means at the first time, further comprising a classification means for classifying the plurality of focus areas into a plurality of groups including focus areas having close focus adjustment states,
The composition change determination means includes a focus adjustment state detected at the first time for each focus area in the group classified at the first time including the focus area of interest selected at the first time. And the focus adjustment state detected at the second time, and the uniformity of the change in the focus adjustment state in the focus area is calculated to determine whether or not a composition change has occurred. Focus adjustment device. The focus adjustment apparatus according to claim 3.
The focus detection means includes the focus area selected at the first time, not all of the plurality of focus areas at the second time, and includes the focus areas selected at the first time. A focus adjustment apparatus that detects the focus adjustment state only for a focus area. The focusing apparatus according to claim 3 or 4,
The focus adjustment unit determines that the composition change has not occurred by the composition change determination unit, and the focus adjustment state of the focus area of interest selected at the first time by the focus detection unit at the second time If the focus area within the group classified at the first time, including the focus area selected at the first time, is not one of the focus areas of interest. A focus adjustment device that adjusts the focus adjustment state based on a focus adjustment state corresponding to a focus area of the lens. In the focus adjustment apparatus according to any one of claims 1 to 5,
The composition change determining means determines that a composition change has occurred when a predetermined time or more has passed between the first time and the second time. In the focus adjustment apparatus according to any one of claims 1 to 6,
The focus detection unit detects the focus adjustment state based on a luminance value of a light beam from a subject,
The composition change determination means has the luminance value detected by the focus detection means at the first time within a predetermined range, and the luminance value detected by the focus detection means at the second time is predetermined. A focus adjusting apparatus, wherein if it is not within the range, it is determined that a composition change has occurred. In the focus adjustment apparatus according to any one of claims 1 to 7,
Further comprising display means for displaying the focus area in which the focus adjustment state detected by the focus detection means is an in-focus state,
When the composition change determination means determines that the composition change has not occurred, the display means determines that the focus adjustment state detected by the focus detection means at the first time is the in-focus state. A focus adjustment device displaying an area. The focus adjustment device according to claim 8.
The display unit displays all of the plurality of focus areas when the focus adjustment state detected by the focus detection unit is the in-focus state for the plurality of focus areas. . A camera comprising the focus adjustment device according to claim 1.