JP4862312B2 - Imaging device and focus control device - Google Patents

Description

  The present invention relates to an image pickup apparatus that picks up an image using a solid-state image pickup element, and a focus control apparatus in the image pickup apparatus, and more particularly to an image pickup apparatus and a focus control apparatus suitable when an XY address scanning type image pickup element is used. .

  In recent years, many image pickup apparatuses such as digital still cameras and digital video cameras are equipped with an autofocus function for automatically focusing on a subject. In general, the autofocus function is realized by detecting the contrast of a captured image based on a high-frequency component of the captured image signal, and determining that the image is in focus when the contrast is high. For example, data called a focus evaluation value obtained by integrating high-frequency components of a captured image signal existing in a predetermined setting area is generated, and the focus lens is moved so that the focus evaluation value becomes maximum.

  Further, when the just focus position (the focus lens position when the focus is achieved) is obtained using such a method, a plurality of focus evaluation values having different filter coefficients or the like are obtained and stored for each position of the focus lens. There has been an apparatus that improves the accuracy of focus control by using such stored data (see, for example, Patent Document 1).

  By the way, a CCD (Charge Coupled Device) type image sensor is the most common as an image sensor used in such an image pickup apparatus, but in recent years, as the number of pixels of a solid-state image sensor increases, CMOS (Complementary Metal Oxide Semiconductor) type image sensors are attracting attention. The CMOS type image sensor has features such that random access of pixel signals is possible, reading is faster than a CCD type image sensor, high sensitivity, and low power consumption.

  However, unlike the so-called global shutter realized by a CCD image sensor, the electronic shutter function of an XY address scanning image pickup device such as a CMOS image sensor sequentially scans a number of pixels arranged two-dimensionally for each pixel row. Thus, it is realized as a so-called rolling shutter (also called a focal plane shutter) that performs signals. For this reason, shifting the exposure period for each row may cause a problem in photographing.

FIG. 7 is a diagram showing the relationship between the exposure timing and the focus lens position when the global shutter is used.
FIG. 7 shows the exposure timing of the image sensor on the upper side and the change in the position of the focus lens at that time on the lower side. In the case of this figure, the focus lens is moved from P53 to P51 between timings T51 to T53. In addition, exposure positions L51 to L53 indicate vertical spatial positions on the image sensor.

  When an image is captured using the global shutter, for example, during timing T51 to T52, exposure is performed in the same exposure period C50 in all pixels on the image sensor. Therefore, the focus lens moves from P53 to P52 in any exposure period of the exposure positions L51 to L53, and the center of gravity G50 of the focus lens position with respect to the exposure time is the midpoint between P52 and P53 in any period. Become. Therefore, the just focus position can be obtained with high accuracy by using the focus evaluation values detected at the exposure positions L51 to L53.

FIG. 8 is a diagram showing the relationship between the exposure timing and the focus lens position when the rolling shutter is used.
In the example of FIG. 8, the focus lens moves from P62 to P61 between timings T61 to T63. When a rolling shutter is used, the charge accumulation start and transfer timing in each pixel is sequentially delayed as it proceeds in the vertical direction. For this reason, for example, when exposure is performed for a predetermined time starting from the timing T61, the exposure periods C61 to C63 at the exposure positions L61 to L63 appear sequentially delayed. Accordingly, the centers of gravity G61 to G63 of the focus lens positions in the exposure periods C61 to C63 are all different positions.
Table 97/25812 (pages 19-23, Fig. 2)

  As in the case of FIG. 8 described above, when imaging is performed using a rolling shutter, when the focus lens moves during exposure, the center of gravity of the focus lens position corresponding to the focus evaluation value is the upper side of the AF (Auto Focus) detection frame. And the lower side will be different. For this reason, the focus evaluation value at each exposure position becomes inaccurate, and there is a problem that the just focus position cannot be obtained with high accuracy. In particular, when trying to increase the focus control speed by increasing the moving speed of the focus lens, the coarseness of the accuracy of the focus control due to the above problem appears more remarkably.

  As a method for avoiding such a problem, it is conceivable to perform control so that the focus lens is not moved during exposure. However, in this case, there is a problem that the time (shutter lag) required from the shutter operation to actual imaging becomes longer, the user operability is lowered, and the user's photographing opportunity is lost.

  The present invention has been made in view of these points, and provides an imaging apparatus with improved autofocus accuracy when an image is captured using an XY address scanning imaging element such as a CMOS image sensor. Objective.

  Another object of the present invention is to provide a focus control device with improved autofocus accuracy when an image is captured using an XY address scanning image sensor such as a CMOS image sensor.

In the present invention, in order to solve the above-described problem, in an imaging apparatus that captures an image using an XY address scanning type solid-state imaging device that is exposed by a rolling shutter system, the solid-state imaging device is positioned at least in the vertical direction on the imaging surface A plurality of detection areas having different detection areas, and extracting means for extracting a high frequency component for each detection area from an image signal obtained by imaging, and obtaining a start time and an end time of an exposure period for each of the plurality of detection areas Centroid calculation for individually calculating the centroid of the position of the focus lens in the exposure period based on the position of the focus lens from the start time to the end time of the exposure period for each detection area for each detection area Corresponding to the extraction results for each detection region by the extraction means and the extraction results That on the basis of the center of gravity from the center of gravity calculating means, the image pickup device, wherein there is provided to have a lens position calculating means for calculating the position of the focus lens when in focus.

  In such an imaging apparatus, the center of gravity of the position of the focus lens with respect to the exposure period is individually calculated for each detection region by the center of gravity calculation unit, and the extraction result of the high frequency components for each detection region is calculated by the lens position calculation unit. Based on the centroid corresponding to each extraction result, the position of the focus lens when the focus is achieved is calculated. For this reason, even when the exposure period is shifted for each detection region, the position of the focus lens with respect to each detection region is correctly associated and the position control of the focus lens is executed.

  According to the imaging apparatus of the present invention, even when the exposure period is shifted for each detection region, the position of the focus lens with respect to each detection region can be correctly associated and the focus lens position can be controlled. Accordingly, it is possible to improve the autofocus accuracy when an image is captured using an XY address scanning type image sensor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a main configuration of an imaging apparatus according to an embodiment of the present invention.
1 includes an optical block 1, a CMOS image sensor (hereinafter abbreviated as a CMOS sensor) 2, an amplifier 3, an A / D converter 4, a camera processing circuit 5, and a microcontroller unit (MCU) 6. To do. In addition, the imaging apparatus includes a motor 12 for driving the focus lens 11 in the optical block 1, a motor control circuit 13 for controlling the focus lens 11, and a timing generator (TG) 14 for driving the CMOS sensor 2. It has been.

  The optical block 1 includes a lens for condensing light from a subject on the CMOS sensor 2, a drive mechanism for moving the lens to perform focusing and zooming, a shutter mechanism, an iris mechanism, and the like. The optical block 1 is provided with a position detector 15 for detecting the position of the focus lens 11.

  In the CMOS sensor 2, a plurality of pixels including a photodiode (photogate), a transfer gate (shutter transistor), a switching transistor (address transistor), an amplifying transistor, and a reset transistor (reset gate) are two-dimensionally formed on a CMOS substrate. And a vertical scanning circuit, a horizontal scanning circuit, an image signal output circuit, and the like are formed. The CMOS sensor 2 is driven based on a timing signal output from the TG 14 and converts incident light from the subject into an electrical signal. Further, on the substrate of the CMOS sensor 2, a CDS (Correlated Double Sampling) circuit for sample-holding a pixel signal is integrally formed. The TG 14 outputs a timing signal under the control of the MCU 6.

  The amplifier 3 applies a gain to the analog image signal output from the CMOS sensor 2 under the control of the MCU 6 and performs a so-called AGC (Auto Gain Control) process. The A / D converter 4 converts the analog image signal output from the amplifier 3 into a digital image signal.

  The camera processing circuit 5 executes various camera signal processes such as AF, AE (Auto Exposure), and white balance adjustment for the image signal from the A / D converter 4, or a part of the process. In the present embodiment, in particular, an AF detection processing circuit 20 that performs detection processing for AF control by the MCU 6 is provided.

  The MCU 6 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls each part of the imaging apparatus by executing a program stored in the ROM. Control.

  The motor control circuit 13 sends a drive control signal to the motor 12 under the control of the MCU 6 to control the position of the focus lens 11. Further, the detection signal output from the position detection unit 15 is supplied to the MCU 6.

  In this image pickup apparatus, a signal received by the CMOS sensor 2 and subjected to photoelectric conversion is subjected to gain adjustment by the amplifier 3, digitally converted by the A / D converter 4, and sequentially supplied to the camera processing circuit 5. The camera processing circuit 5 performs image quality correction processing on the supplied digital image signal, and finally converts it into a luminance signal (Y) and a color difference signal (RY, BY) and outputs it.

  The image data output from the camera processing circuit 5 is supplied to a graphic I / F (not shown) and converted into a display image signal, whereby a camera-through image is displayed on a monitor (not shown). When the MCU 6 is instructed to record an image by a user input operation from an input unit (not shown), the image data from the camera processing circuit 5 is supplied to an encoder (not shown), and a predetermined compression encoding process is performed. And recorded on a recording medium (not shown). When recording a still image, the camera processing circuit 5 supplies one frame of image data to the encoder, and when recording a moving image, the processed image data is continuously supplied to the encoder. .

Next, autofocus control in this imaging apparatus will be described.
The autofocus function of this imaging apparatus is basically such that a focus evaluation value indicating contrast is obtained by integrating a high frequency component of a predetermined area on an image by the AF detection processing circuit 20 of the camera processing circuit 5. This is realized by moving the focus lens 11 so that the focus evaluation value is maximized by the above process. In addition, a plurality of AF detection frames are set in the light receiving area of the image sensor, and the just focus position is obtained using the focus evaluation value obtained for each AF detection frame within one frame (or within one field). It achieves both efficiency and improved focus control accuracy.

  However, when an XY scanning type image sensor that performs exposure using the rolling shutter method, such as the CMOS sensor 2, the exposure period is shifted for each row. Therefore, when the focus lens 11 moves during exposure, There is also a deviation between the focus evaluation values from the plurality of AF detection frames and the corresponding focus lens positions. For this reason, if the focus evaluation value by each AF detection frame is associated with the same focus lens position, the accuracy of the focus control is lowered. Therefore, in this embodiment, the focus accuracy is improved by individually obtaining the center of gravity of the focus lens position with respect to the exposure time for each AF detection frame existing in the vertical direction of the screen.

FIG. 2 is a diagram illustrating a first setting example of the AF detection frame.
In FIG. 2, it is assumed that the image signal is scanned from the upper left direction to the lower right direction in the figure (the same applies to FIGS. 5 and 6 described later). At this time, AF detection frames W1 to W3 are set in the vertical direction of the screen. In each of the AF detection frames W1 to W3, for example, focus evaluation values are detected by detecting image signals in the vertical center lines L1 to L3. The AF detection frame W4 is set in a region that includes all the AF detection frames W1 to W3. For example, in the normal imaging mode, autofocus control is performed based on the focus evaluation values from the AF detection frames W1 to W3, and the focus from the AF detection frame W4 is when the subject to be focused is at the center of the screen. Different uses such as using evaluation values are performed.

FIG. 3 is a diagram illustrating an example of the focus lens position during exposure by the rolling shutter.
FIG. 3 shows an example in which the focus lens 11 moves from the position P1 to the position P5 between the timings T0 and T4, and thereafter the focus lens 11 stops at the position P5. Here, the focus lens positions (P1 to P5) are expressed as relative position information with reference to the reference position P0.

  In addition, when exposure with a rolling shutter is performed when the focus lens position changes in this way, a shift occurs in the exposure period for each line. In the example of FIG. 3, the exposure period C1 in the center line L1 of the AF detection frame W1 is timings T1 to T5, the exposure period C2 in the center line L2 of the AF detection frame W2 is timings T2 to T6, and the AF detection frame W3. The exposure period C3 in the center line L3 is timings T3 to T7.

  The MCU 6 takes in the focus evaluation values in the AF detection frames W1 to W3 from the image signal for one frame (or one field) from the AF detection processing circuit 20, and also performs a focus lens in a period including the exposure periods C1 to C3. The position transition is stored together with the time information. Then, the center of gravity of the focus lens position corresponding to each of the exposure periods C1 to C3 is calculated by the process shown in FIG. The MCU 6 can detect the focus lens position from the drive control information for the focus lens 11 by the MCU 6 and the position information supplied from the position detection unit 15 through the motor control circuit 13 as described later.

FIG. 4 is a flowchart showing a flow of processing for calculating the center of gravity of the focus lens position.
[Step ST1] The MCU 6 obtains the start time and end time of the exposure period in each AF detection frame. In the example of FIG. 3, the start time and the end time are obtained for the exposure periods C1 to C3 in the AF detection frames W1 to W3, respectively. For example, the start time and end time of the exposure period C1 are obtained as T1 and T5, respectively. The obtained time information is temporarily stored in, for example, a RAM in the MCU 6.

  [Step ST2] The MCU 6 determines the focus lens position in each exposure period. For example, when the MCU 6 can detect the focus lens position at regular intervals, the focus lens positions at regular intervals in each of the exposure periods C1 to C3 are obtained and temporarily stored in a RAM or the like. Alternatively, the MCU 6 may store a movement history of the focus lens 11 in each exposure period C1 to C3 (for example, a time at the start and end of movement and a focus lens position). In any case, the MCU 6 needs to be able to determine the focus lens position in each of the exposure periods C1 to C3 at a plurality of timings.

  [Step ST3] The MCU 6 obtains an integral value of the focus lens position in each exposure period. When the start time and end time of the exposure period are Ts and Te, respectively, and the focus lens position with respect to time is represented by a function f (t), the integral value S can be obtained by the following equation (1).

In the example of FIG. 3, for example, when the MCU 6 acquires the focus lens position at regular time intervals in step ST2, the values of the focus lens position from the start to the end should be integrated for each exposure period C1 to C3. That's fine. Further, when the MCU 6 stores the movement history of the focus lens 11 in step ST2, the integral values S1 to S3 corresponding to the exposure periods C1 to C3 can be calculated by the following equations.
S1 = (P5 + P2) * (T4-T1) / 2 + P5 * (T5-T4)
S2 = (P5 + P3) × (T4-T2) / 2 + P5 × (T6-T4)
S3 = (P5 + P4) × (T4−T3) / 2 + P5 × (T7−T4)
[Step ST4] The MCU 6 divides the calculated integral value S by the exposure time to obtain the center of gravity G. In the example of FIG. 3, the centroids G1 to G3 corresponding to the exposure periods C1 to C3 are calculated by the following equations.
G1 = S1 / (T5-T1)
G2 = S2 / (T6-T2)
G3 = S3 / (T7-T3)
In the above description, the MCU 6 calculates the centroids G1 to G3 after all the exposure periods C1 to C3 are completed. However, necessary information is sequentially fetched for each of the exposure periods C1 to C3, and the respective centroids G1. The calculation of ~ G3 may be executed in parallel.

  When the center of gravity G is obtained by the above procedure, the MCU 6 recognizes the focus lens position corresponding to the focus evaluation value in each exposure period as the position of the obtained center of gravity (for example, the focus evaluation value in the exposure period C1). The corresponding focus lens position is set as the position of the center of gravity G1), which is used for calculation for obtaining the just focus position. Thereby, even if the focus lens 11 is moved during exposure, the shift of the focus lens position corresponding to the focus evaluation value is corrected by the center of gravity, and an accurate focus lens position (that is, the center of gravity) is associated with each focus evaluation value. Therefore, the accuracy of autofocus control can be improved. Further, since it is not necessary to stop the focus lens 11 during exposure, the shutter lag can be shortened and the autofocus control can be speeded up.

  Further, as shown in FIG. 2, even when a plurality of AF detection frames are set in the vertical direction of the screen, an accurate focus lens position can be associated with the focus evaluation value in each AF detection frame. The accuracy of autofocus control can be further improved.

Here, FIG. 5 is a diagram illustrating a second setting example of the AF detection frame.
In FIG. 5, four AF detection frames W11 to W14 are set in the vertical direction on the image sensor, which is larger than in the case of FIG. In this way, by setting more AF detection frames and acquiring focus evaluation values, the position of the center of gravity calculated for each AF detection frame is associated with each focus evaluation value and used for autofocus control. Accuracy can be improved.

FIG. 6 is a diagram illustrating a third setting example of the AF detection frame.
In FIG. 6, five AF detection frames W21 to W25 are set on the image sensor, and among these, the AF detection frames W22 to W24 are set at the same position in the vertical direction. In such a case, the MCU 6 individually obtains the center of gravity for the AF detection frames W21, W23, and W25 having different vertical positions, and associates the position of the center of gravity as the focus lens position with respect to the focus evaluation value in each AF detection frame. . For the AF detection frames W22 and W24, the calculation of the center of gravity is not performed, and the position of the center of gravity in the AF detection frame W23 is associated as the focus lens position with respect to each focus evaluation value.

  As described above, the center of gravity calculation is performed from only one of the AF detection frames having the same vertical position (for example, one close to the horizontal position of another AF detection frame having a different vertical position). As a result, it is possible to reduce the processing load of the MCU 6 while obtaining the accuracy improvement effect of the autofocus control.

Lastly, a supplemental description will be given of the focus lens position detection method in the MCU 6.
The MCU 6 can detect the focus lens position information used for the calculation of the center of gravity from the drive control information for the focus lens 11 by the MCU 6 itself and the position information supplied from the position detection unit 15 through the motor control circuit 13. For example, when a stepping motor is used as the actuator of the focus lens 11, the MCU 6 receives focus lens position information from the position detection unit 15 via the motor control circuit 13 at the initial stage of control of the focus lens 11, and thereafter. Detects the focus lens position based on the drive control information of the focus lens 11 by itself. Further, since there may be a position shift due to a step-out or the like, the MCU 6 appropriately receives information from the position detection unit 15, corrects the focus lens position, and uses the corrected position information as drive control of the focus lens 11 and the corrected position information. You may use for a gravity center calculation.

  As the position detection unit 15 in this case, for example, a photo interrupter that detects the edge position of the focus lens 11 and outputs a pulse can be used. In this case, there are a method that can detect edge switching as the absolute position of the focus lens 11, a method that detects the position according to edge switching after the focus lens 11 is once sent to a fixed position (reference position), and the like. is there. In addition to this, a method of using an encoder as the position detector 15 and detecting the absolute position of the focus lens 11 as several bits of information can be applied.

  On the other hand, when the actuator for the focus lens 11 is a linear motor or the like that operates non-linearly from the start to the stop of movement, the motor control circuit 13 receives an instruction from the focus lens 11 from the MCU 6. Based on the position detection information from the position detector 15, servo control (closed loop control) is performed so that the focus lens 11 moves to the instructed target position, and the position information at that time is notified to the MCU 6. For example, an MR sensor or a Hall element is used as the position detection unit 15. In addition, position detection information is output from the position detection unit 15 at regular time intervals, and the position accuracy can be improved by shortening the output interval. Then, when the position information notified from the motor control circuit 13 is used for the gravity center calculation, the MCU 6 approximates the focus lens position (the function f (t) described above) according to the output interval of the position detection information. You may do it.

  In the above embodiment, a case where a CMOS image sensor is used as the image sensor has been described. However, when another XY address scanning image sensor such as a MOS image sensor other than a CMOS image sensor is used. The present invention is also applicable. The present invention can also be applied to various imaging devices using XY address scanning type imaging devices, and devices such as mobile phones and PDAs (Personal Digital Assistants) having such an imaging function. . Furthermore, the present invention can also be applied to control processing at the time of imaging with a small camera such as a videophone or game software connected to a PC (personal computer) or the like.

  Further, the above processing functions can be realized by a computer. In that case, a program describing the processing contents of the functions that the apparatus should have (such as the gravity center calculation function by the MCU 6) is provided. And the said processing function is implement | achieved on a computer by running the program with a computer. The program describing the processing contents can be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include a magnetic recording device, an optical disk, a magneto-optical disk, and a semiconductor memory.

  In order to distribute the program, for example, portable recording media such as an optical disk and a semiconductor memory on which the program is recorded are sold. It is also possible to store the program in a storage device of a server computer and transfer the program from the server computer to another computer via a network.

  The computer that executes the program stores, for example, the program recorded on the portable recording medium or the program transferred from the server computer in its own storage device. Then, the computer reads the program from its own storage device and executes processing according to the program. The computer can also read the program directly from the portable recording medium and execute processing according to the program. Further, each time the program is transferred from the server computer, the computer can sequentially execute processing according to the received program.

It is a block diagram which shows the principal part structure of the imaging device which concerns on embodiment of this invention. It is a figure which shows the 1st example of a setting of AF detection frame. It is a figure which shows the example of the focus lens position during exposure by a rolling shutter. It is a flowchart which shows the flow of a process which calculates the gravity center of a focus lens position. It is a figure which shows the 2nd example of a setting of AF detection frame. It is a figure which shows the 3rd example of a setting of AF detection frame. It is a figure which shows the relationship between the exposure timing at the time of using a global shutter, and a focus lens position. It is a figure which shows the relationship between the exposure timing at the time of using a rolling shutter, and a focus lens position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical block, 2 ... CMOS type image sensor (CMOS sensor), 3 ... Amplifier, 4 ... A / D converter, 5 ... Camera processing circuit, 6 ... Microcontroller unit (MCU), 11 ... ... Focus lens, 12 ... Motor, 13 ... Motor control circuit, 14 ... Timing generator (TG), 15 ... Position detector, 20 ... AF detection processing circuit

Claims (9)

In an imaging apparatus that captures an image using an XY address scanning solid-state imaging device that is exposed by a rolling shutter system ,
An extraction means for setting a plurality of detection areas at different positions in the vertical direction on the imaging surface of the solid-state imaging device, and extracting a high-frequency component for each detection area from an image signal obtained by imaging;
Obtaining the start time and end time of the exposure period for each of the plurality of detection areas, and for each detection area, based on the position of the focus lens from the start time to the end time of the exposure period for each detection area, Centroid calculating means for individually calculating the centroid of the position of the focus lens in the exposure period ;
Lens position calculation means for calculating the position of the focus lens when the focus is achieved based on the extraction result for each detection region by the extraction means and the centroid from the centroid calculation means corresponding to each of the extraction results; ,
An imaging device comprising:   The center-of-gravity calculation means calculates the center of gravity by integrating the position of the focus lens in the exposure period in each detection region and dividing the integrated value by the length of the exposure period. Item 2. The imaging device according to Item 1. The extraction means extracts a high frequency component from a horizontal image signal passing through the approximate center of each detection region,
The center-of-gravity calculating means calculates a center of gravity of the position of the focus lens with respect to an exposure period at an approximate center of each detection region;
The imaging apparatus according to claim 1.   The center-of-gravity calculation means calculates the center of gravity of the position of the focus lens based on the position of the focus lens at a plurality of timings in the exposure period in each detection region. Imaging device.   The center-of-gravity calculating means calculates the center of gravity of the position of the focus lens based on the position and time of the focus lens at the start and stop of the movement of the focus lens during the exposure period in each detection region. The imaging apparatus according to claim 1.   The center-of-gravity calculation means has an exposure period corresponding to one of the plurality of detection areas when a plurality of the detection areas having different positions relative to the horizontal direction on the imaging surface of the solid-state imaging device are set. The imaging apparatus according to claim 1, wherein the center of gravity is calculated based on a position of the focus lens. In a focus control apparatus that automatically controls the position of a focus lens so as to be focused based on a detection value of an image signal captured by an XY address scanning type solid-state imaging device that is exposed by a rolling shutter system ,
A plurality of detection regions having different positions at least in the vertical direction on the imaging surface of the solid-state image sensor, and acquiring means for acquiring a value of a high-frequency component extracted for each detection region from an image signal obtained by imaging; ,
Obtaining the start time and end time of the exposure period for each of the plurality of detection areas, and for each detection area, based on the position of the focus lens from the start time to the end time of the exposure period for each detection area, Centroid calculating means for individually calculating the centroid of the position of the focus lens in the exposure period ;
Based on the extraction result of the high frequency component for each detection region acquired by the acquisition unit and the center of gravity from the center of gravity calculation unit corresponding to the extraction result, the position of the focus lens when the focus is achieved is calculated. Lens position calculating means for
A focus control device comprising: In a focus control method for automatically controlling the position of a focus lens so as to be in focus based on a detection value of an image signal captured by an XY address scanning type solid-state image sensor that is exposed by a rolling shutter system ,
When the acquisition unit sets a plurality of detection regions having different positions at least in the vertical direction on the imaging surface of the solid-state imaging device, the high-frequency component extracted for each detection region from the image signal obtained by imaging Obtaining a value;
The center-of-gravity calculation means obtains the start time and end time of the exposure period for each of the plurality of detection areas, and the position of the focus lens from the start time to the end time of the exposure period for each detection area for each detection area And separately calculating the center of gravity of the position of the focus lens in the exposure period ,
The lens position calculation means is based on the extraction result of the high-frequency component for each detection region acquired by the acquisition means and the centroid from the centroid calculation means corresponding to the extraction result, and when the focus is achieved Calculating the position of the focus lens;
A focus control method comprising: In a focus control program for causing a computer to execute a process of automatically controlling the position of a focus lens so as to be focused based on a detection value of an image signal captured by an XY address scanning type solid-state imaging device that is exposed by a rolling shutter system .
A plurality of detection regions having different positions at least in the vertical direction are set on the imaging surface of the solid-state imaging device, and acquiring means for acquiring a value of a high-frequency component extracted for each of the detection regions from an image signal obtained by imaging,
Obtaining the start time and end time of the exposure period for each of the plurality of detection areas, and for each detection area, based on the position of the focus lens from the start time to the end time of the exposure period for each detection area, Centroid calculating means for individually calculating the centroid of the position of the focus lens in the exposure period ;
Based on the extraction result of the high frequency component for each detection region acquired by the acquisition unit and the center of gravity from the center of gravity calculation unit corresponding to the extraction result, the position of the focus lens when the focus is achieved is calculated. Lens position calculating means
A focus control program for causing the computer to function as:

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