JP6349678B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection apparatus and an imaging apparatus.

  Conventionally, the focus detection areas are grouped according to the brightness of each of the plurality of focus detection areas, and the charges (signals) read out from the line sensor based on the brightness of the group having the largest number of focus detection areas belonging to the same group. ) Has been proposed (see Patent Document 1).

JP 2012-63449 A

  In the focus detection apparatus of Patent Document 1, when gain is determined based on a group on the high luminance side, signal data with a sufficient output level is obtained in the focus detection region of that group. However, in the focus detection areas of other groups, the output level is significantly lower than the saturation level of the line sensor, and therefore signal data with an appropriate output level cannot be obtained when the contrast of the subject is low.

  An object of the present invention is to provide a focus detection apparatus and an imaging apparatus that can set an appropriate accumulation time.

  The focus detection device of the present invention is set in a focus detection sensor having a plurality of focus detection areas that receive a light beam from a subject and generate charges, and in each of the focus detection areas of the focus detection sensor. Output means for outputting signal data based on the charge generated in the accumulation time; and the charge generated in the accumulation time previously set in the plurality of focus detection areas, based on the charge generated in the plurality of focus detection areas. A saturation time calculation means for calculating a charge saturation time which is a time until the charge is saturated, and a charge generated in the first focus detection area among the plurality of focus detection areas with the previously set accumulation time; A first ratio, which is a ratio of charges generated in the other focus detection areas, is calculated, and a second focus detection among the plurality of focus detection areas is performed during the previously set accumulation time. Calculating a second ratio, which is a ratio of the charge generated in the other focus detection area to the charge generated in the area, and the ratio is used for focus detection among the first ratio and the second ratio. The charge saturation time in the first focus detection region or the second focus detection region, in which the ratio of the number of the focus detection regions within a predetermined range that is equal to or higher than the noise level ratio of the sensor is calculated, An accumulation time setting means for setting the accumulation time is provided.
  The imaging device of the present invention is configured to include a focus detection device.

  According to the present invention, it is possible to provide a focus detection apparatus and an imaging apparatus that can set an appropriate accumulation time.

It is a schematic block diagram of the camera 1 in 1st Embodiment. 3 is a conceptual diagram illustrating a configuration of a phase difference AF detection area 151 in a phase difference AF detection unit 15. FIG. It is a conceptual diagram which shows line sensor S1-S7 arrange | positioned corresponding to the AF area of each row | line | column. 4 is a flowchart illustrating a processing procedure when an AF operation of the camera 1 is performed in the control device 30. 4 is a flowchart illustrating a processing procedure of AF sensor control by an AF-CCD control unit 31 according to the first embodiment. 4 is a flowchart illustrating a processing procedure of AF sensor control by an AF-CCD control unit 31 according to the first embodiment. It is a flowchart which shows the process sequence of AF sensor control by AF-CCD control part 31A of 2nd Embodiment. It is a flowchart which shows the process sequence of AF sensor control by AF-CCD control part 31A of 2nd Embodiment.

  Hereinafter, embodiments of a focus detection device and an imaging device according to the present invention will be described with reference to the drawings. Here, an embodiment in which the focus detection apparatus according to the present invention is applied to a camera 1 as an imaging apparatus will be described.

[First Embodiment]
First, the camera 1 according to the first embodiment will be described. FIG. 1 is a schematic configuration diagram of a camera 1 in the first embodiment.

  As shown in FIG. 1, the camera 1 includes a camera body 10 and an imaging lens 20 configured to be detachable from the camera body 10. The camera 1 of this embodiment is a so-called digital single-lens reflex camera.

  The camera body 10 includes an image sensor 11, a quick return mirror 12A, a sub mirror 12B, a finder optical system 13, a photometric unit 14, a phase difference AF detection unit 15 as a focus detection sensor and detection means, and an operation member. 16 and a control device 30.

  The image pickup device 11 is configured by a solid-state image pickup device such as a CCD or a CMOS that outputs a charge converted from subject light as a charge signal. In the image sensor 11, pixels corresponding to red (R), green (G), and blue (B) colors are arranged in a predetermined arrangement pattern. The image sensor 11 captures image information on an image formation plane by the image forming optical system of the image pickup lens 20 and outputs the image information to the control device 30 as an image signal corresponding to color information and luminance information corresponding to each pixel.

  The quick return mirror 12A is a reflecting member configured to be movable to two different positions in the camera 1. That is, the quick return mirror 12A is movable between an action position (see FIG. 1) interposed in the optical path from the imaging optical system of the imaging lens 20 to the imaging element 11 and a retracted position not interposed in the optical path. It is configured. The quick return mirror 12A reflects the incident light beam to the finder optical system 13 (finder screen 13A) at the operating position. A part of the quick return mirror 12A is formed with a semi-transmissive region that transmits a part of the incident light beam.

  The sub mirror 12B is a reflecting member provided on the back side of the quick return mirror 12A. The sub mirror 12B reflects the incident light beam that has passed through the semi-transmissive area of the quick return mirror 12A toward the phase difference AF detection unit 15 in the quick return mirror 12A that has moved to the operating position.

  The finder optical system 13 includes a finder screen 13A, a pentaprism 13B, and an eyepiece lens 13C.

  The finder screen 13 </ b> A is provided at a position optically equivalent to the image sensor 11. An incident light beam guided by the quick return mirror 12A forms an image on the finder screen 13A. The pentaprism 13B and the eyepiece 13C are optical systems that enable the photographer to visually recognize the subject image formed on the viewfinder screen 13A as an erect image.

  The photometric unit 14 includes a photometric lens 14A and a photometric sensor 14B. The photometric lens 14A guides the subject image formed on the finder screen 13A via the pentaprism 13B to the photometric sensor 14B. As with the image sensor 11, the photometric sensor 14 </ b> B includes pixels corresponding to each color of red (R), green (G), and blue (B) arranged in a predetermined arrangement pattern, and is imaged by a lens optical system. Image information on the image plane is captured.

  Then, the photometric sensor 14B outputs a photometric signal corresponding to the color information and luminance information corresponding to each pixel to the control device 30. The control device 30 detects the brightness of the imaging surface based on the photometric signal from the photometric sensor 14B and determines the exposure.

  The operation member 16 includes various switches (not shown) for operating the camera 1. For example, the operation member 16 is instructed to select a mode selection switch for selecting the operation mode of the camera 1, an area selection switch for selecting an AF area (described later), a focus adjustment (AF) start, and an instruction for shooting Release button etc. are included.

  The phase difference AF detection unit 15 includes line sensors S1 to S7 (described later) as focus detection sensors. The incident light flux that has been transmitted through the semi-transmissive region of the quick return mirror 12A and reflected by the sub mirror 12B is incident on the line sensors S1 to S7. In addition, the phase difference AF detection unit 15 functions as a function of the detection unit by supplying the charges detected by the line sensors S1 to S7 to the AF-CCD control unit 31 as signal data controlled by a preset accumulation time and gain. Output.

  FIG. 2 is a conceptual diagram showing the configuration of the phase difference AF detection area 151 in the phase difference AF detection unit 15. As shown in FIG. 2, the phase difference AF detection area 151 is provided with a plurality of AF areas (ranging areas) 153 as focus detection areas at predetermined positions in the imaging area 152. In the present embodiment, one focus detection range (row) is constituted by five AF areas 153 arranged in the vertical direction. This focus detection range is arranged in seven rows, and a total of 35 AF areas 153 are arranged. Hereinafter, the AF area 153 illustrated in FIG. 2 is also referred to as an “AF area” as appropriate.

  FIG. 3 is a conceptual diagram showing line sensors S1 to S7 (hereinafter collectively referred to as “line sensor S”) arranged corresponding to the AF area of each column. The line sensors S1 to S7 are arranged so as to correspond to the focus detection range of each column.

  In FIG. 2, each area A to E indicated by a broken line indicates the vertical position of the focus detection area. Each AF area 153 can be represented by a line sensor S number (1 to 7) and a region code (A to E). For example, the AF area 153 at the center of the phase difference AF detection area 151 is “C1”.

  The line sensor S is a charge storage type photoelectric conversion element array (CCD line sensor or the like) in which a plurality of photoelectric conversion elements that output a charge signal according to the intensity of subject light are arranged in a line. In the line sensor S, one photoelectric conversion element is arranged in an area corresponding to each AF area. A pair of luminous fluxes divided into two by passing through different regions of the imaging lens 20 (see FIG. 1) are divided into two by an aperture mask (not shown), and then the pair of subject images are line sensors S. Re-imaged in the corresponding region of. The line sensor S detects the luminance of the formed subject image as an electric charge. That is, the line sensor S accumulates charges proportional to the luminance of the pair of subject images over a set accumulation time. As a result, a charge signal corresponding to the luminance of the pair of subject images is output from the line sensor S. The charge signal output from the line sensor S is amplified with a preset gain in an amplifier circuit (not shown), and then converted into digital signal data in an A / D converter (not shown). The output level of the signal data is represented by the peak value of the charge signal × gain.

  The control device 30 is configured by a CPU, a memory, and the like (not shown), and integrally controls the operation of the camera 1. In addition, the control device 30 detects the brightness of the imaging surface based on the photometric signal from the photometric sensor 14B, and determines the exposure.

  Further, as shown in FIG. 1, the control device 30 includes an AF-CCD control unit 31, a defocus calculation unit 32, a focus area position determination unit 33, and a lens as functional units related to focus adjustment (AF). A drive amount calculation unit 34, a lens drive control unit 35, and a background region / face region extraction unit 36 are provided.

  The AF-CCD control unit 31 reads the signal data from the phase difference AF detection unit 15 and outputs the signal data to the defocus calculation unit 32. The charge accumulation time in the line sensor S of the phase difference AF detector 15 and the gain of the amplifier circuit are set by the AF-CCD controller 31.

  The AF-CCD control unit 31 calculates the saturation time of each AF area to be controlled based on the previously set accumulation time of the AF area to be controlled as a function of the saturation time calculation means.

  As a function of the accumulation time control means, the AF-CCD control unit 31 sets a saturation level range (to be described later) as a main luminance distribution of the focus detection range based on the saturation time of each AF area calculated in the above control. The accumulation time in accumulation control is set according to the specified saturation level range.

  Each control of the AF-CCD control unit 31 will be described later. In the present embodiment, the phase difference AF detection unit 15 and the AF-CCD control unit 31 constitute a focus detection apparatus according to the present invention.

  Based on the signal data output from the AF-CCD control unit 31, the defocus calculation unit 32 calculates a defocus amount that represents the focus adjustment state (focus amount) of the imaging lens 20.

  The focus area position determination unit 33 determines an AF area 153 that finally focuses the imaging lens 20 based on the defocus amount calculated by the defocus calculation unit 32.

  The lens driving amount calculation unit 34 has a focus that the imaging lens 20 has based on the defocus amount calculated by the defocus calculation unit 32 corresponding to the AF area determined by the user or the focus area position determination unit 33. The driving amount of the adjusting lens (lens group L2) is calculated.

  Here, the lens drive amount is calculated by calculating the lens target position that is the target of the drive position of the focus adjustment lens (lens group L2). The lens target position corresponds to the position of the focus adjustment lens (lens group L2) where the defocus amount is almost zero.

  The lens drive control unit 35 controls the driving of the lens driving motor 22 of the imaging lens 20 based on the lens driving amount calculated by the lens driving amount calculating unit 34, that is, the lens target position with respect to the focus adjustment lens (lens group L2). Output a signal. In response to this drive control signal, the lens drive motor 22 drives the focus adjustment lens (lens group L2) and moves it to the lens target position, thereby performing focus adjustment.

  Based on the signal data output from the AF-CCD control unit 31, the background region / face region extraction unit 36 extracts a high luminance portion serving as a background region from the imaging region 152. The background area / face area extraction unit 36 extracts a face area from the signal data output from the AF-CCD control unit 31 by a technique such as pattern matching.

  The imaging lens 20 includes a plurality of lens groups L1, L2, and L3 that constitute an imaging optical system, and a lens driving motor 22 inside the lens barrel 21. The lens group L2 is a focus adjustment lens that can move in the direction of the optical axis OA and adjust the imaging position. The lens group L2 is configured to be movable to the subject side or the image sensor 11 side along the optical axis OA direction by the lens driving motor 22. The driving of the lens driving motor 22 is controlled by a control device 30 provided on the camera body 10 side.

  Next, a processing procedure when performing the AF operation in the camera 1 configured as described above will be described. FIG. 4 is a flowchart illustrating a processing procedure when the control device 30 performs the AF operation of the camera 1. The processing in this flowchart is started when the user performs an operation such as half-pressing the release button (operation member 16) and instructs the camera 1 to perform AF driving.

  In step S101 shown in FIG. 4, the AF-CCD control unit 31 causes the phase difference AF detection unit 15 (line sensor S) to perform charge accumulation control as AF sensor control. The signal data obtained by this accumulation control is output from the phase difference AF detection unit 15 to the defocus calculation unit 32 via the AF-CCD control unit 31.

  In step S <b> 102, the defocus calculation unit 32 calculates an image shift amount by correlation calculation based on the signal data output from the AF-CCD control unit 31, and calculates the defocus amount.

In step S103, the focus area position determination unit 33 executes an AF area position determination routine (not shown).
In step S104, the lens drive amount calculation unit 34 executes a lens drive amount calculation routine (not shown).

  In step S105, the lens drive control unit 35 outputs a drive control signal to the lens drive motor 22 of the imaging lens 20 in accordance with the result of the lens drive amount calculation of the lens drive amount calculation unit 34 in step S104.

  Next, the AF sensor control (subroutine) in step S101 in FIG. 4 will be described. 5 and 6 are flowcharts showing the processing procedure of AF sensor control by the AF-CCD control unit 31. FIG. The processes of the flowcharts shown in FIGS. 5 and 6 are executed for each of the line sensors S1 to S7. Here, description will be given as processing of an arbitrary line sensor S.

  In step S201 shown in FIG. 5, the AF-CCD control unit 31 determines whether or not the line sensor S has been activated. If the determination of the AF-CCD control unit 31 is “YES” in step S201, the process proceeds to step S203. If the determination of the AF-CCD control unit 31 is “NO” in step S201, the process proceeds to step S202.

In step S202, the AF-CCD control unit 31 executes startup processing such as initialization.
In step S203, the AF-CCD control unit 31 calculates the saturation time of each AF area to be controlled based on the previously set accumulation time of the AF area to be controlled.

  When the background area exclusion mode is set in advance, as a pre-process in step S203, the background area / face area extraction unit 36 (see FIG. 1) uses an AF area (focus detection) that is not to be controlled. Area) is executed. That is, the background area / face area extraction unit 36 excludes the corresponding AF area from being excluded from the control target when there is a high-luminance part that becomes the background area from the imaging area 152 (see FIG. 2), and the remaining AF The area is controlled.

  In step S204, the AF-CCD control unit 31 sets the AF area with the shortest saturation time as the AF area with the highest luminance, and the ratio of saturation time in other AF areas (hereinafter referred to as the ratio Hb% of the saturation time). , Also referred to as “saturation time ratio”). Then, the AF-CCD control unit 31 sets the calculated saturation time ratio (%) within a preset saturation time ratio Hbmin (%) to Hbmax (%) (hereinafter also referred to as “saturation level range”). Count the number of areas that enter.

Here, it demonstrates, referring Table 1 below. In Table 1, in the focus detection range corresponding to the line sensor S1 (see FIG. 3), the corresponding AF areas (focus detection regions) are represented by A1, B1, C1, D1, and E1.

  As shown in Table 1, in the focus detection range corresponding to the line sensor S1, the AF area (maximum brightness AF area) with the shortest saturation time is B1 (5 ms). Here, assuming that the saturation time ratio Hb% in B1 is 85% (5 ms × 0.85 = 4.25 ms), the saturation time ratio in other AF areas (85% 4.25 ms as a reference) ) Is 15.2% to 53.1%. When the saturation level range set for the AF area with the highest luminance is 25% (Hbmin) to 85% (Hbmax), the number of areas that fall within this saturation level range is three areas A1, B1, and C1. It becomes.

  In this embodiment, the upper limit (Hbmax) of the saturation level range set for the AF area with the highest luminance is set to be equal to or lower than the saturation level (100%) of the line sensor S in order to reduce the influence of overflow. . In the present embodiment, an example in which Hbmax is set to 85% is shown.

  In step S205, the AF-CCD control unit 31 sets the AF area with the longest saturation time as the AF area with the lowest luminance, and the saturation time ratio (%) in the other AF areas with respect to the saturation time ratio Hd%. Is calculated. Then, the AF-CCD control unit 31 counts the number of AF areas where the calculated saturation time ratio (%) falls within a saturation level range of preset saturation time ratios Hdmin (%) to Hdmax (%).

  As shown in Table 1, in the focus detection range corresponding to the line sensor S1, the AF area having the longest saturation time (the AF area having the lowest luminance) is E1 (28 ms). Here, if the saturation time ratio Hd% in E1 is 25% (28 ms × 0.25 = 7 ms), the saturation time ratio in other AF areas (ratio when 25% is 7 ms as a reference) is 35. 0.0% to 140.0%. If the saturation level range set for the AF area with the lowest luminance is 25% (Hdmin) to 100% (Hdmax), the number of areas that fall within this saturation level range is A1, C1, D1, E1. There will be 4 areas.

  In this embodiment, the lower limit value (Hdmin) of the saturation level range set for the AF area with the lowest luminance is set to be equal to or higher than the noise level of the line sensor S as the focus detection sensor in order to reduce the influence of noise. Is done. In this embodiment, an example in which Hdmin is set to 25% is shown.

  In step S206, the AF-CCD control unit 31 sets an AF area that is an intermediate area of the saturation time (an intermediate area between the shortest saturation time and the longest saturation time) as an AF area of intermediate luminance, and the saturation time ratio Hc. With respect to%, the saturation time ratio (%) in other AF areas is calculated. Then, the AF-CCD control unit 31 counts the number of AF areas in which the calculated saturation time ratio (%) falls within the saturation level range of preset saturation time ratios Hcmin (%) to Hcmax (%).

  As shown in Table 1, in the focus detection range corresponding to the line sensor S1, the AF area that is an intermediate region of the saturation time is C1 (12 ms). Here, assuming that the ratio Hc% of the saturation time in C1 is 50% (12 ms × 0.5 = 6 ms), the saturation time ratio in other AF areas (ratio based on 6 ms of 50%) is 21. 4% to 120.0%. When the saturation level range set for the AF area of intermediate luminance is 25% (Hcmin) to 100% (Hcmax), the number of areas that fall within this saturation level range is 3 of A1, C1, D1, and so on. It becomes an area.

  In step S207 shown in FIG. 6, the AF-CCD control unit 31 includes the saturation level range in which the saturation time ratio of the AF area (A1, B1, C1, D1, E1) is the largest among the above three saturation level ranges. (Saturation level range of most counts) is specified as the saturation level range that is the main luminance distribution of the focus detection range corresponding to the line sensor S1. Then, the AF-CCD control unit 31 sets a saturation time that is a reference for the specified saturation level range as an accumulation time in the current control.

  In the present embodiment, among the three saturation level ranges, the saturation level range in which the saturation time ratio of the AF area (A1, B1, C1, D1, E1) is the largest is included in the AF area with the lowest luminance of 4 areas. Corresponding Hdmin (%) to Hdmax (%). Therefore, the AF-CCD control unit 31 saturates the saturation level range from Hdmin (%) to Hdmax (%) corresponding to the AF area with the lowest luminance to be the main luminance distribution of the focus detection range corresponding to the line sensor S1. Specify as a level range. Then, the AF-CCD control unit 31 sets a saturation time of 7 ms (see Table 1), which serves as a reference for the specified saturation level range, as an accumulation time in the current control.

  In step S207, the AF-CCD control unit 31 selects a saturation level range on the higher luminance side when there are a plurality of saturation level ranges that are included most in the AF area among the three saturation level ranges. To do. For example, as the saturation level range most frequently included in the AF area, the saturation level range from Hdmin (%) to Hdmax (%) corresponding to the AF area with the highest luminance, and Hcmin (%) corresponding to the AF area with the intermediate luminance, It is assumed that there is a saturation level range of Hcmax (%). In this case, the AF-CCD control unit 31 selects a saturation level range from Hdmin (%) to Hdmax (%) corresponding to the AF area with the highest luminance, which is the saturation level range on the higher luminance side.

  In step S208 shown in FIG. 6, the AF-CCD control unit 31 sets a gain for the line sensor S of the phase difference AF detection unit 15 based on the result of the previous accumulation control. Here, it is desirable to set a gain as low as possible in order to reduce noise in the signal data to be output. However, when there is a limit on the storage time during continuous shooting, the gain is set according to the upper limit value of the storage time.

In step S209, the AF-CCD control unit 31 resets the accumulation time set in step S207 in accordance with the gain set in step S208.
In step S210, the AF-CCD control unit 31 performs accumulation control of the line sensor S according to the accumulation time reset in step S209. In this accumulation control, charges are accumulated in the line sensor S according to the set accumulation time. The charge accumulated in the line sensor S is transferred to the amplifier circuit as a charge signal and amplified with a preset gain. The charge signal amplified by the amplifier circuit is further converted into digital signal data by the A / D converter.

In step S <b> 211, the AF-CCD control unit 31 reads the signal data output from the phase difference AF detection unit 15, performs correction processing such as sensitivity non-uniformity correction, and outputs the result to the defocus calculation unit 32.
After the completion of this subroutine, the processing of the AF-CCD control unit 31 proceeds to step S102 of the main routine shown in FIG.

The focus detection apparatus according to the first embodiment described above has the following effects.
In the focus detection apparatus of the first embodiment, the saturation level range that is the main luminance distribution of the focus detection range is specified based on the saturation time of each AF area, and accumulation in accumulation control is performed according to the saturation level range. Time is set. According to this, it is possible to set an accumulation time with less influence of overflow or noise in as many focus detection regions as possible in each focus detection range. Therefore, according to the focus detection apparatus of the first embodiment, when performing accumulation control of a plurality of focus detection areas based on one accumulation time, appropriate accumulation times are set in as many focus detection areas as possible. can do.

  In the focus detection apparatus of the first embodiment, the saturation level range that includes the largest saturation time ratio of the AF area among the plurality of preset saturation level ranges is the main luminance distribution of the focus detection range. Specified as the saturation level range. According to this, the saturation level range most suitable for the luminance distribution of the captured image can be specified. Therefore, according to the focus detection apparatus of the first embodiment, it is possible to set a more appropriate accumulation time with less influence of overflow and noise in each focus detection range.

  Further, in the focus detection apparatus of the first embodiment, when there are a plurality of saturation level ranges that include the largest number of AF areas among the plurality of saturation level ranges, the saturation level range on the higher luminance side is selected. . Therefore, according to the focus detection apparatus of the first embodiment, signal data with a higher output level can be obtained while suppressing overflow in as many focus detection regions as possible.

[Second Embodiment]
Next, the camera 1A of the second embodiment will be described. Since the basic configuration of the camera 1A in the second embodiment is the same as that of the camera 1 (see FIG. 1) of the first embodiment, the description thereof is omitted.

  The AF-CCD control unit 31A (see FIG. 1) of the second embodiment changes the saturation level range of high luminance, low luminance, and intermediate luminance according to the set gain. Specifically, the AF-CCD control unit 31A temporarily sets the gain of each AF area, and if there is at least one AF area where the temporarily set gain is High, the lower limit value of each saturation level range is high. Change to Since other processes are the same as those in the first embodiment, description thereof will be omitted.

  FIGS. 7 and 8 are flowcharts showing a processing procedure of AF sensor control by the AF-CCD control unit 31A of the second embodiment. The processing in steps S301 to S303 illustrated in FIG. 7 corresponds to the processing in steps S201 to S203 illustrated in FIG. 8 corresponds to the processes of steps S204 to S206 shown in FIG. 5 and the processes of steps S207 to S211 shown in FIG. Hereinafter, steps S304 to S306 illustrated in FIG. 7 will be mainly described as processing characteristic of the present embodiment, and description of processing overlapping with the processing of the first embodiment described above will be omitted.

  In step S304 shown in FIG. 7, the AF-CCD control unit 31A temporarily sets the gain of each AF area based on the saturation time of each AF area calculated in step S303. In this temporary setting, a setting is made after estimating how much gain should be set based on the previously set gain and accumulation time, and whether the signal data can be appropriately controlled. In the present embodiment, the gain can be set in three stages of Low, Middle (> Low), and High (> Middle) in the amplifier circuit (not shown) of the phase difference AF detection unit 15.

  In step S305, the AF-CCD control unit 31A determines whether or not there is an AF area where the temporarily set gain is High. If the determination of the AF-CCD control unit 31 is “YES” in step S305, the process proceeds to step S306. If the determination of the AF-CCD control unit 31 is “NO” in step S305, the process proceeds to step S307 (see FIG. 8).

  In step S306, the AF-CCD control unit 31A changes so that the lower limit value of the saturation level range used in the subsequent processing in steps S307 to S309 (corresponding to steps S204 to S206 in FIG. 5) is increased. In the present embodiment, the AF-CCD control unit 31A changes Hbmin, Hdmin, and Hcmin from 25% to 35%. In step 306, the saturation time ratio Hd% in the AF area where the saturation time is the longest is changed from 25% to 35%.

  When the lower limit value of the saturation level range is changed in step S306, the saturation level range in step S307 is 35% (Hbmin) to 85% (Hbmax) as shown in FIG. In addition, the saturation level range in step S308 is 35% (Hdmin) to 100% (Hdmax). The saturation level range in step 308 is calculated based on a saturation time ratio of 35%. Furthermore, the saturation level range in step S309 is 35% (Hcmin) to 100% (Hcmax). Note that if the determination in step S305 is NO and the process in step S306 is skipped, the lower limit value of the saturation level range in steps S307 to S309 remains 25% (set value in the first embodiment).

Here, the setting of the accumulation time in the second embodiment will be described with reference to Table 2 below. The AF areas (A1 to E1) shown in Table 2 indicate the focus detection range corresponding to the line sensor S1 as in Table 1 (first embodiment).

  As shown in Table 2, in the focus detection range corresponding to the line sensor S1, the AF area having the shortest saturation time (the AF area with the highest luminance) is B1 (2 ms). Here, since the ratio Hb% of the saturation time in B1 is 85% (2 ms × 0.85 = 1.7 ms), the saturation time ratio in other AF areas (based on 1.7 ms of 85%) The ratio) is 3.4% to 85.0%. If the saturation level range set for the AF area with the highest luminance is 35% (Hbmin) to 85% (Hbmax), the number of areas that fall within this saturation level range is one area of B1.

  Further, as shown in Table 2, in the focus detection range corresponding to the line sensor S1, the AF area having the longest saturation time (the AF area having the lowest luminance) is E1 (50 ms). Here, the saturation time ratio Hd% in E1 is 35% (50 ms × 0.35 = 17.5 ms), so the saturation time ratio in other AF areas (35% 17.5 ms as a reference) The ratio) is 35.0% to 875.0%. If the saturation level range set for the lowest luminance AF area is 35% (Hdmin) to 100% (Hdmax), the number of areas that fall within this saturation level range is three areas C1, D1, and E1. It becomes.

  Further, as shown in Table 2, in the focus detection range corresponding to the line sensor S1, the AF area that is an intermediate region of the saturation time is C1 (18 ms). Here, since the ratio Hc% of the saturation time in C1 is 50% (18 ms × 0.5 = 9 ms), the saturation time ratio in other AF areas (ratio based on 9 ms of 50%) is It becomes 18.0%-450.0%. If the saturation level range set for the AF area of intermediate luminance is 35% (Hcmin) to 100% (Hcmax), the number of areas that fall within this saturation level range is three areas A1, C1, and D1. It becomes.

  In the present embodiment, among the three saturation level ranges, the saturation level range in which the saturation time ratio of the AF area (A1, B1, C1, D1, E1) is the largest is the AF area having the lowest luminance with 3 areas. Corresponding Hdmin (%) to Hdmax (%), and Hcmin (%) to Hcmax (%) corresponding to the AF area having the intermediate luminance of 3 areas. As described above, when there are a plurality of saturation level ranges including the most AF areas, the saturation level range on the higher luminance side is selected. For this reason, the AF-CCD control unit 31A saturates the saturation level range from Hcmin (%) to Hcmax (%) corresponding to the AF area of intermediate luminance to the main luminance distribution of the focus detection range corresponding to the line sensor S1. Specify as a level range. Then, the AF-CCD control unit 31A sets a saturation time of 9 ms (see Table 2), which serves as a reference for the specified saturation level range, as an accumulation time in the current control.

The focus detection apparatus according to the second embodiment described above has the following effects.
In the focus detection apparatus of the second embodiment, if there is even one AF area where the temporarily set gain is High, the lower limit value of each saturation level range is changed. In general, when the luminance of the subject is extremely low, the accumulation time becomes long, so that it may not be within the set accumulation time. Therefore, when there is an AF area where the temporarily set gain is high, that is, when there is an AF area with extremely low luminance, the saturation on the high luminance side is increased by increasing the lower limit value of each saturation level range. Since the number of AF areas that enter the low luminance or intermediate saturation level range is larger than the number of AF areas that fall within the level range, the accumulation time corresponding to the low luminance or intermediate saturation level range is set. . Therefore, according to the focus detection apparatus of the second embodiment, when accumulation control of a plurality of focus detection areas is performed based on one accumulation time, as much as possible even when a dark subject is included in a captured image. An appropriate accumulation time can be set in the focus detection region.

[Deformation]
Without being limited to the embodiment described above, the present invention can be variously modified and changed as described below, and these are also within the scope of the present invention.

  In step S207 shown in FIG. 6, when the AF area (A1, B1, C1, D1, E1) includes a face detection area or an area to be prioritized (hereinafter collectively referred to as “priority area”). Alternatively, the number of areas of these priority areas may be counted, and the saturation level range with the largest number of counts may be selected based on the priority order of steps S204> S205> S206 shown in FIG.

  In the mode in which priority areas are set as described above, when these priority areas are not counted, the line sensor adopts the accumulation time set by another line sensor in which the priority areas are counted. As described above, it is preferable that the accumulation time in the mode in which the priority area is set is set to a time during which overflow does not easily occur, such as the calculated saturation time × 0.5.

  Moreover, although the said embodiment and modification can be used in combination suitably, since the structure of each embodiment is clear by illustration and description, detailed description is abbreviate | omitted. Furthermore, the present invention is not limited by the embodiment described above.

  DESCRIPTION OF SYMBOLS 1,1A: Camera, 10: Camera main body, 11: Image pick-up element, 15: Phase difference AF detection part, 20: Imaging lens, 30: Control apparatus, 31, 31A: AF-CCD control part, 32: Defocus calculating part 33: Focus area position determination unit 34: Lens drive amount calculation unit 35: Lens drive control unit 36: Background region / face region extraction unit

Claims (5)

  A focus detection sensor having a plurality of focus detection areas for receiving a light beam from a subject and generating a charge;
  In the focus detection area of each of the focus detection sensors, output means for outputting signal data based on charges generated in a set accumulation time;
  A saturation time for calculating a charge saturation time, which is a time until the charge in each of the plurality of focus detection regions is saturated, based on the charge generated during the previously set accumulation time of the plurality of focus detection regions. A calculation means;
  A first ratio, which is a ratio of charges generated in the other focus detection areas to charges generated in the first focus detection area among the plurality of focus detection areas, is calculated at the previously set accumulation time. And
  A second ratio that is a ratio of charges generated in another focus detection area to charges generated in the second focus detection area among the plurality of focus detection areas is calculated at the previously set accumulation time. And
  Of the first ratio and the second ratio, the first ratio is calculated as a ratio in which the number of the focus detection areas is within a predetermined range in which the ratio is equal to or greater than a noise level ratio of the focus detection sensor. Accumulation time setting means for setting the charge saturation time in the focus detection area or the second focus detection area as the accumulation time;
  A focus detection apparatus. The focus detection apparatus according to claim 1,
The predetermined range is a focus detection device that is different in the first ratio and the second ratio . The focus detection apparatus according to claim 2,
The focus detection apparatus , wherein the predetermined range at the first ratio is a higher ratio range than the predetermined range at the second ratio . In the focus detection apparatus according to any one of claims 1 to 3,
Wherein the predetermined range, the focus detection device is changed according to the set gain to the output means. An imaging device provided with the focus detection apparatus of any one of Claim 1 to 4 .

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