JP2011252956A - Autofocus control device and autofocus camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately shorten a focus adjusting time by autofocus drive control.SOLUTION: An autofocus control device comprises an image pick-up element 2 that images a subject image through an imaging optical system 1; optical system drive controlling sections 4 and 10 that control a movement of a focus adjusting optical system in an optical axis direction in the imaging optical system 1 and a stop of the movement of the focus adjusting optical system therein; an evaluation value calculating section 4 that calculates a focus evaluation value using an image pick-up signal from the image pick-up element 2 in response to the stop of the movement of the focus adjusting optical system by an optical system drive section 9; a calculation section 4 that calculates a focus position based upon a calculated value by the evaluation value calculating section 4; and a selecting section 4 that selects a first drive mode, which restricts electric power supply to driving of the focus adjusting optical system at the time the focus adjusting optical system is stopped or a second drive mode, which does not restrict the electric power supply thereto at the time the focus adjusting optical system is stopped.

Description

  The present invention relates to an autofocus control device and an autofocus camera.

  There is known an autofocus device that calculates a contrast value (focus evaluation value) of captured images sequentially obtained by an image sensor while moving a focus lens, and detects a focus position that maximizes the contrast (Patent Document). 1). In the conventional technology, when the shutter button is fully pressed (shooting instructions are given), the focus lens is moved faster or the contrast value calculation interval is narrowed to reduce the focus. The adjustment processing time is shortened.

JP 2006-259688 A

  In the prior art, the relationship between the focus evaluation value and the focus lens position interval before and after the shooting instruction is different, so that there is a possibility that the calculation accuracy of the focus position may be different before and after the shooting instruction.

  An autofocus control device according to the present invention controls an imaging element that captures a subject image through a photographing optical system, and movement of the focus adjustment optical system in the optical axis direction and stop of movement of the focus adjustment optical system in the photographing optical system. An optical system drive control unit, an evaluation value calculation unit that calculates a focus evaluation value using an imaging signal from the imaging device in response to the stop of movement of the focus adjustment optical system by the optical system drive unit, and a calculation by the evaluation value calculation unit A calculation unit that calculates a focus position based on the value, and a first drive mode that restricts supply power for driving the focus adjustment optical system when the focus adjustment optical system is stopped, or supply power is not restricted when the focus adjustment optical system is stopped And a selection unit that selects the second drive mode.

  The focus adjustment time can be appropriately shortened by the autofocus drive control according to the present invention.

It is a block diagram explaining the principal part structure of the electronic camera carrying the autofocus control apparatus by one embodiment of this invention. It is a flowchart explaining the flow of imaging | photography sequence processing. It is a flowchart explaining the detail of AF process. It is a flowchart explaining the detail of an initial position drive process. It is a flowchart explaining the detail of a search drive start process. It is a flowchart explaining the detail of a search stop process. It is a flowchart explaining the detail of a focusing drive process. It is a figure which shows an example of the relationship between the position of a focus lens, and a contrast value. It is a figure which shows an example of the relationship between the elapsed time in AF process, and the position of a focus lens. It is a figure which compares AF processing time in case an excitation continuation flag is 1 and 0. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram for explaining the main configuration of an electronic camera equipped with an autofocus control device according to an embodiment of the present invention. The electronic camera is controlled by the CPU 4.

  The taking lens 1 forms a subject image on the image pickup surface of the image pickup device 2. The image sensor 2 is configured by, for example, a CMOS image sensor. The image sensor 2 captures a subject image and outputs an image signal to the image signal processing circuit 3. The image signal processing circuit 3 includes an AFE (Analog Front End) circuit, an A / D conversion circuit, and a signal processing circuit.

  The AFE circuit performs correlated double sampling, gain adjustment, and the like on the input image signal. The A / D conversion circuit converts the image signal after gain adjustment into digital image data. The signal processing circuit performs image processing on the image data. The image processing includes, for example, γ conversion processing, contour enhancement processing, filter processing, color temperature adjustment (white balance adjustment) processing, image compression / expansion processing, and the like.

  The CPU 4 inputs a signal output from each block in the camera, performs a predetermined calculation, and outputs a control signal based on the calculation result to each block. The CPU 4 further performs a focus evaluation value calculation for detecting the focus position by the photographing lens 1 based on the contrast information of the captured image. The focus evaluation value calculation will be described later.

  The LCD monitor 5 displays a captured image or an operation menu according to an instruction from the CPU 4. The power switch 6 is turned on / off in conjunction with a pressing operation of a power button (not shown), and sends an on operation signal or an off operation signal to the CPU 4.

  The half-push switch 7 and the release switch 8 are turned on / off in conjunction with a pressing operation of a release button (not shown). The half-press switch 7 is turned on when the release button is half-pressed and outputs a half-press operation signal to the CPU 4. The half-push switch 7 is turned off when the half-push operation of the release button is released and stops outputting the half-push operation signal.

  The release switch 8 is turned on when the release button is pressed down to a full-press position deeper than the half-press operation, and outputs a full-press operation signal to the CPU 4. The release switch 8 is turned off when the release button full-press operation is released, and stops the output of the full-press operation signal. In the following description, a state in which a half-press operation signal is output to the CPU 4 is represented as S1 on, and a state in which a full-press operation signal is output to the CPU 4 (that is, a state in which shooting is instructed) is represented as S2 on.

  The stepping motor 9A includes, for example, a stator (fixed body) and a rotor (rotating body). The lens driving mechanism 9 changes the predetermined energization phase according to the lens driving signal from the lens driving control circuit 10 to the stepping motor 9A. The focus lens constituting the photographic lens 1 is moved back and forth in the optical axis direction using the rotational force of the rotor rotating according to the inputted predetermined energization phase as a driving force source. Thereby, the focus adjustment of the electronic camera is performed. The lens drive control circuit 10 outputs a lens drive signal (a signal for instructing a lens drive direction and a lens drive amount) to the lens drive mechanism 9 in accordance with an instruction from the CPU 4. In the present embodiment, the state where the stepping motor is energized is the excitation on state, and the state where the stepping motor is not energized is the excitation off state. Further, in the stationary state of the rotor, the rotor is constrained with respect to the stator when excitation is on, and the rotor is not constrained with respect to the stator when excitation is off.

  The voltage detection circuit 11 detects the voltage of the loaded battery 21 and sends a signal indicating the detection voltage to the CPU 4. The CPU 4 determines the remaining amount of the battery 21 based on the detection voltage. The buffer memory 12 is used as a primary storage memory during image data processing and a flag value storage memory. The nonvolatile memory 13 records a program (details of processing will be described later) executed by the CPU 4.

<Focus adjustment>
The CPU 4 performs focus adjustment by a contrast detection method based on data from pixels corresponding to the focus detection area among the pixels included in the image sensor 2. For example, while moving the focus lens from the infinity side (the position where the subject at infinity is in focus) to the close side (the position where the subject at the shortest shooting distance is in focus), search for the lens position where the contrast is maximum The focus of the electronic camera is adjusted by moving the focus lens to the lens position.

  Specifically, filter processing is performed so as to remove low-frequency components, particularly DC components, of pixel data corresponding to the focus detection area, and the image data after the filter processing is integrated. In the integration process, the absolute values of the image data are integrated in order to integrate the differences due to the high frequency components.

  The CPU 4 obtains a focus evaluation value (contrast value) using the integrated value. FIG. 8 is a diagram illustrating an example of the relationship between the position of the focus lens in the photographing lens 1 and the contrast value. In FIG. 8, the horizontal axis represents the position of the focus lens, and the vertical axis represents the contrast value. The lens position corresponding to the peak of the contrast curve is the focus position of the focus lens with respect to the main subject.

  In the present embodiment, the focus lens is moved from the infinity side to the close side and then moved to the lens position corresponding to the peak of the contrast value “mountain”, but the focus lens is moved from the close side. The focus lens may be moved to the lens position corresponding to the peak of the “peak” of the contrast value after moving all the way to the infinity side.

<Shooting sequence processing>
The flow of the camera process including the focus adjustment process described above will be described with reference to the flowchart illustrated in FIG. FIG. 2 is a diagram for explaining the flow of imaging sequence processing executed by the CPU 4. When the battery 21 is loaded, the CPU 4 activates the process shown in FIG.

  In step S1 of FIG. 2, the CPU 4 determines whether or not the power is on. The CPU 4 makes an affirmative decision in step S1 in the case of a power-on state (a state in which a power-on process to be described later is performed), and proceeds to step S4. In the case of a power-off state (a state before the power-on process), step S1 Is negatively determined, and the process proceeds to step S2.

  In step S2, the CPU 4 determines whether or not the power switch 6 is turned on. When the on operation signal is input from the power switch 6, the CPU 4 makes a positive determination in step S2 and proceeds to step S3. When the on operation signal is not input from the power switch 6, the CPU 4 makes a negative determination in step S2 and proceeds to step S1. Return to. When returning to step S1, the above-described processing is repeated.

  In step S3, the CPU 4 performs a power-on process and proceeds to step S4. The power-on process refers to initializing each block by starting energization of each block in the camera from a power circuit (not shown). In step S4, the CPU 4 determines whether or not the power switch 6 is turned off. When the off operation signal is input from the power switch 6, the CPU 4 makes a positive determination in step S4 and proceeds to step S10. When the off operation signal is not input from the power switch 6, the CPU 4 makes a negative determination in step S4 and proceeds to step S5. Proceed to

  In step S10, the CPU 4 performs a power-off process and returns to step S1. The power-off process is to end energization of each block in the camera from a power supply circuit (not shown) after the process in process is completed. After returning to step S1, the above-described processing is repeated.

  In step S5, the CPU 4 determines whether or not S1 is on. If S1 is on, CPU 4 makes an affirmative decision in step S5 and proceeds to step S6, and if not S1 on, the CPU 4 makes a negative decision and returns to step S1. When returning to step S1, the above-described processing is repeated.

  In step S6, the CPU 4 performs an AF (autofocus) process and proceeds to step S7. Details of the AF processing will be described later. In step S7, the CPU 4 determines whether or not S1 is kept on. The CPU 4 makes an affirmative determination in step S7 when S1 is continued and proceeds to step S8, and if S1 is not continued, the CPU 4 makes a negative determination in step S7 and returns to step S1. When returning to step S1, the above-described processing is repeated.

  In step S8, the CPU 4 determines whether or not S2 is on. When S2 is on, CPU 4 makes a positive determination in step S8 and proceeds to step S9. When it is not S2 on, it makes a negative determination in step S8 and returns to step S7. When returning to step S7, the above-described processing is repeated.

  In step S9, the CPU 4 performs an imaging process and returns to step S1. As a result, a series of photographing processes is completed. CPU4 repeats the process mentioned above, when returning to step S1.

<AF processing>
Details of the AF processing will be described with reference to a flowchart illustrated in FIG. In step S61 of FIG. 3, the CPU 4 sets an initial value 0 to the excitation continuation flag and proceeds to step S62. The excitation continuation flag is a flag that is set to 1 when S2 ON is detected during movement of the focus lens.

  In step S62, the CPU 4 performs contrast AF initial setting and proceeds to step S63. In step S63, the CPU 4 sends an instruction to the lens drive control circuit 10 to drive the focus lens to the initial position (search start position), drives the stepping motor 9A of the lens drive mechanism 9, and proceeds to step S64 (initial). Position-driven processing). Details of the initial position driving process will be described later.

  In step S64, the CPU 4 acquires the focus evaluation value (contrast value) at the search start position and the corresponding lens position information, and proceeds to step S65. The lens position information can be calculated based on, for example, the number of control pulses sent from the lens drive control circuit 10 to the lens drive mechanism 9.

  In step S65, the CPU 4 sends an instruction to the lens drive control circuit 10 to search and drive the focus lens at a predetermined speed in a predetermined direction (in this example, a direction from the infinity side to the close side), and the lens drive mechanism 9 The search drive process of the stepping motor 9A is started and the process proceeds to step S66 (search drive start process). Details of the search drive start process will be described later.

  In step S66, the CPU 4 acquires a focus evaluation value (contrast value) and corresponding lens position information every predetermined time, and performs a process of determining a peak of a “mountain” of the contrast curve, and then proceeds to step S67.

  In step S67, the CPU 4 determines whether or not S2 is on. The CPU 4 makes a positive determination in step S67 when S2 is on and proceeds to step S72. If not, the CPU 4 makes a negative determination in step S67 and proceeds to step S68. In step S72, the CPU 4 sets 1 in the excitation continuation flag and proceeds to step S68.

  In step S68, the CPU 4 determines whether or not the position of the focus lens is the search end point (that is, the search end position). The CPU 4 makes an affirmative decision in step S68 when the search end point is (the closest end in this example), and proceeds to step S69. If not, the CPU 4 makes a negative decision in step S68 and returns to step S66. When returning to step S66, the above-described processing is repeated.

  In step S69, the CPU 4 sends an instruction to the lens drive control circuit 10 to stop the drive of the focus lens, performs a process of stopping the stepping motor 9A of the lens drive mechanism 9, and proceeds to step S70 (search stop process). Details of the search stop process will be described later.

  In step S70, the CPU 4 determines the peak of the “mountain” of the contrast curve, and proceeds to step S71. In step S71, the CPU 4 sends an instruction to the lens drive control circuit 10, moves the focus lens to the lens position corresponding to the peak of the “peak” of the contrast value (focus drive process), and ends the process of FIG. . Details of the focusing drive process will be described later.

<Initial position driving process>
The details of the initial position driving process will be described with reference to the flowchart illustrated in FIG. In step S631 in FIG. 4, the CPU 4 sends an instruction to the drive control circuit 10 to instruct pre-excitation of the lens driving mechanism 9 for the stepping motor 9A for a predetermined time (eg, Tmsec), and proceeds to step S632. Pre-excitation refers to a drive preparation state in which a predetermined voltage is applied to the motor (or a predetermined current is supplied) before the stepping motor 9A is rotated. In the drive preparation state, the rotor is attracted to a stator (both not shown) to be in a fixed state.

  FIG. 9 is a diagram illustrating an example of the relationship between the elapsed time during the AF process and the position of the focus lens. In FIG. 9, the horizontal axis represents the position of the focus lens, and the vertical axis represents the elapsed time. Step S631 corresponds to pre-excitation (A) in FIG.

  In step S632 of FIG. 4, the CPU 4 sends an instruction to the drive control circuit 10 to start the initial position drive of the focus lens. As a result, the focus lens starts moving toward the infinity side, which is the search start position.

  In step S633, the CPU 4 determines whether or not S2 is on. The CPU 4 makes a positive determination in step S633 when S2 is on and proceeds to step S637. If not, the CPU 4 makes a negative determination in step S633 and proceeds to step S634. In step S637, the CPU 4 sets 1 in the excitation continuation flag and proceeds to step S634.

  In step S634, the CPU 4 determines whether or not the position of the focus lens is the initial position (that is, the search start position). When the CPU 4 has reached the initial position (in this example, the infinity end), the CPU 4 makes an affirmative determination in step S634 and proceeds to step S635. If the initial position has not been reached, the CPU 4 makes a negative determination and proceeds to step S633. Return. When returning to step S633, the above-described processing is repeated. The loop process repeated between step S633 and step S634 corresponds to the initial position drive (B) in FIG.

  In step S635, the CPU 4 sends an instruction to the drive control circuit 10, stops the initial position drive of the focus lens, waits (waits) for a predetermined time (for example, Tmsec), and proceeds to step S636. The predetermined time (for example, Tmsec) corresponds to the time required for the focus lens position to stabilize after stopping the initial position drive of the focus lens. For example, when the focus lens shifts from the moving state to the stopped state due to a stop instruction from the CPU 4, an inertial force is applied to the focus lens in a certain direction. It takes time. During standby, voltage application (or current supply) to the stepping motor 9A is maintained (post-excitation). This standby corresponds to the post-excitation (C) in FIG.

  In step S636, the CPU 4 determines whether the excitation continuation flag is 1. When the excitation continuation flag is 1 (that is, when S2 ON is detected during the movement of the focus lens), the CPU 4 makes a positive determination in step S636 and ends the process of FIG. That is, when S2 ON is detected during the movement of the focus lens, the initial position driving process is ended while maintaining the excitation state of the stepping motor 9A.

  On the other hand, if the excitation continuation flag is not 1 (that is, S2 ON is not detected during movement of the focus lens), the CPU 4 makes a negative determination in step S636 and proceeds to step S638. In step S638, the CPU 4 sends an instruction to the drive control circuit 10, turns off the excitation to the stepping motor 9A, and ends the process shown in FIG. That is, when S2 ON is not detected during the movement of the focus lens, the initial position driving process is terminated without exciting the stepping motor 9A.

<Search drive start processing>
The details of the search drive start process will be described with reference to the flowchart illustrated in FIG. In step S651 in FIG. 5, the CPU 4 waits for VD synchronization and proceeds to step S652. The VD synchronization waiting means waiting until an image signal captured by the image sensor 2 is output to the image signal processing circuit 3. By waiting for the VD synchronization, the focus evaluation value is calculated after waiting for completion of image data for one frame. Step S651 corresponds to the VD synchronization wait (D) in FIG.

  In step S652, the CPU 4 determines whether or not the excitation continuation flag is 1. If the excitation continuation flag is 1 (that is, S2 on is detected during movement of the focus lens), the CPU 4 makes a positive determination in step S652 and proceeds to step S653. If S2 ON is detected during the movement of the focus lens, the stepping motor 9A can be driven as it is because the excitation state for the stepping motor 9A is maintained.

  On the other hand, if the excitation continuation flag is not 1 (that is, S2 ON is not detected during movement of the focus lens), the CPU 4 makes a negative determination in step S652 and proceeds to step S654. In step S654, the CPU 4 sends an instruction to the drive control circuit 10 to instruct pre-excitation of the lens driving mechanism 9 for the stepping motor 9A for a predetermined time (eg, Tmsec), and proceeds to step S653. The pre-excitation causes the rotor to be attracted to a stator (both not shown) to be in a fixed state, and the stepping motor 9A can be driven. Step S654 corresponds to the pre-excitation (E) in FIG.

  In step S653, the CPU 4 sends an instruction to the drive control circuit 10 to start search driving of the focus lens. As a result, the focus lens starts moving toward the search end (closest end), which is the search end position. Thereafter, the search stop process corresponds to the search drive (F) in FIG.

<Search stop processing>
The details of the search stop process will be described with reference to the flowchart illustrated in FIG. In step S691 of FIG. 6, the CPU 4 sends an instruction to the drive control circuit 10, stops the search driving of the focus lens, waits (waits) for a predetermined time (eg, Tmsec), and proceeds to step S692. The predetermined time (for example, Tmsec) corresponds to the time required for the focus lens position to stabilize after stopping. During standby, the excitation state of the stepping motor 9A is maintained (post-excitation). This standby corresponds to the post-excitation (G) in FIG.

  In step S692, the CPU 4 determines whether or not the excitation continuation flag is 1. When the excitation continuation flag is 1 (that is, when S2 ON is detected during movement of the focus lens), the CPU 4 makes an affirmative decision in step S692 and ends the process of FIG. That is, when S2 is on while the focus lens is moving, the search drive is terminated while maintaining the excitation state of the stepping motor 9A.

  On the other hand, if the excitation continuation flag is not 1 (that is, S2 ON is not detected during movement of the focus lens), the CPU 4 makes a negative determination in step S692 and proceeds to step S693. In step S693, the CPU 4 sends an instruction to the drive control circuit 10, turns off the excitation to the stepping motor 9A, and ends the process shown in FIG. If S2 ON is not detected during the movement of the focus lens, the search drive is terminated without exciting the stepping motor 9A.

<Focus drive processing>
Details of the focusing drive processing will be described with reference to a flowchart illustrated in FIG. In step S711 in FIG. 7, the CPU 4 performs in-focus display and in-focus sound processing, and proceeds to step S712. Specifically, the display color of the frame indicating the focus detection area displayed on the LCD monitor 5 is made different from that before focusing, or a predetermined sound indicating focusing is reproduced from a speaker (not shown).

  In step S712, the CPU 4 determines whether or not the excitation continuation flag is 1. When the excitation continuation flag is 1 (that is, when S2 ON is detected during movement of the focus lens), the CPU 4 makes a positive determination in step S712 and proceeds to step S713. That is, when S2 ON is detected during the movement of the focus lens, the stepping motor 9A can be driven as it is because the excitation state for the stepping motor 9A is maintained.

  On the other hand, if the excitation continuation flag is not 1 (that is, S2 on is not detected during movement of the focus lens), the CPU 4 makes a negative determination in step S712 and proceeds to step S723. In step S723, the CPU 4 sends an instruction to the drive control circuit 10 to instruct pre-excitation of the lens driving mechanism 9 for the stepping motor 9A for a predetermined time (eg, Tmsec), and proceeds to step S713. The pre-excitation causes the rotor to be attracted to a stator (both not shown) to be in a fixed state, and the stepping motor 9A can be driven. Step S723 corresponds to pre-excitation (I) in FIG.

  In step S713, the CPU 4 sends an instruction to the drive control circuit 10 to start focusing driving of the focus lens. The drive target position in this case is a position on the search start side corresponding to the backlash from the in-focus position. As a result, the focus lens starts to move from the search end position to the drive target position. The subsequent steps up to step 714 correspond to the focusing drive (J) in FIG.

  In step S714, the CPU 4 determines whether or not the position of the focus lens is the drive target position (that is, the search start position side corresponding to the backlash from the in-focus position). If the CPU 4 has reached the drive target position, the CPU 4 makes an affirmative determination in step S714 and proceeds to step S715. If the drive target position has not been reached, the CPU 4 makes a negative determination in step S714 and repeats the determination process.

  In step S715, the CPU 4 sends an instruction to the drive control circuit 10, stops driving the focus lens, waits (waits) for a predetermined time (for example, Tmsec), and proceeds to step S716. The predetermined time (for example, Tmsec) corresponds to the time required for the focus lens position to stabilize after stopping. During standby, voltage application (or current supply) to the stepping motor 9A is maintained (post-excitation). This standby corresponds to post-excitation (K) in FIG.

  In step S716, the CPU 4 determines whether or not the excitation continuation flag is 1. If the excitation continuation flag is 1 (that is, S2 on is detected during movement of the focus lens), the CPU 4 makes a positive determination in step S716 and proceeds to step S718. When S2 ON is detected during the movement of the focus lens, the process proceeds to the next while maintaining the excitation state of the stepping motor 9A.

  On the other hand, if the excitation continuation flag is not 1 (that is, S2 is not detected while the focus lens is moving), the CPU 4 makes a negative determination in step S716 and proceeds to step S717. In step S717, the CPU 4 sends an instruction to the drive control circuit 10, turns off the excitation to the stepping motor 9A, and proceeds to step S718. That is, when S2 ON is not detected during the movement of the focus lens, the process proceeds to the next state without exciting the stepping motor 9A.

  In step S718, the CPU 4 determines whether or not the excitation continuation flag is 1. If the excitation continuation flag is 1 (that is, S2 on is detected during movement of the focus lens), the CPU 4 makes a positive determination in step S718 and proceeds to step S719. That is, when S2 ON is detected during the movement of the focus lens, the stepping motor 9A can be driven as it is because the excitation state for the stepping motor 9A is maintained.

  On the other hand, if the excitation continuation flag is not 1 (that is, S2 is not detected while the focus lens is moving), the CPU 4 makes a negative determination in step S718 and proceeds to step S724. In step S724, the CPU 4 sends an instruction to the drive control circuit 10 to instruct pre-excitation of the lens driving mechanism 9 for the stepping motor 9A for a predetermined time (eg, Tmsec), and the process proceeds to step S719. The pre-excitation causes the rotor to be attracted to a stator (both not shown) to be in a fixed state, and the stepping motor 9A can be driven. Step S724 corresponds to the pre-excitation (L) in FIG.

  In step S719, the CPU 4 sends an instruction to the drive control circuit 10 to start backlash driving of the focus lens. The backlash drive is performed in the same direction as the search drive. As a result, the focus lens starts moving to the in-focus position. The steps up to step 720 correspond to the backlash drive (M) in FIG.

  In step S720, the CPU 4 determines whether or not the position of the focus lens is the in-focus position. When the CPU 4 has reached the in-focus position, the CPU 4 makes a positive determination in step S720 and proceeds to step S721. When the CPU 4 has not reached the in-focus position, the CPU 4 makes a negative determination and repeats the determination process.

  In step S721, the CPU 4 sends an instruction to the drive control circuit 10, stops driving the focus lens, waits for a predetermined time (for example, Tmsec) (waits), and proceeds to step S722. The predetermined time (for example, Tmsec) corresponds to the time required for the focus lens position to stabilize after stopping. During standby, the excitation state for the stepping motor 9A is maintained (post-excitation). This standby corresponds to post-excitation (N) in FIG.

  In step S722, the CPU 4 sends an instruction to the drive control circuit 10, turns off the excitation to the stepping motor 9A, and ends the process shown in FIG.

  FIG. 10 shows a case where the excitation continuation flag is 1 (that is, S2 on is detected during movement of the focus lens accompanying the AF process) and an excitation continuation flag is 0 (that is, S2 is on during movement of the focus lens accompanying the AF process). It is a figure which compares AF processing time in the case where is not detected). The upper diagram shows the breakdown of the processing time when the excitation continuation flag is 0, and the lower diagram shows the breakdown of the processing time when the excitation continuation flag is 1.

  According to FIG. 10, when the excitation continuation flag is 1, the excitation off of step S638 (FIG. 4), step S693 (FIG. 6), and step S717 (FIG. 7) performed when the excitation continuation flag is 0 is performed. Therefore, the pre-excitation (E) in step S654 (FIG. 5), the pre-excitation (I) in step S723 (FIG. 7), and the pre-excitation (L) in step S724 (FIG. 7) can be omitted. Thereby, the AF processing time can be shortened by the time required for these pre-excitations (3 × Tmsec in this example). The shortening time 3T varies depending on the specifications of the stepping motor 9A to be used, the power supply voltage, and the like, but it leads to a shortening of several tens of milliseconds, for example.

According to the embodiment described above, the following operational effects can be obtained.
(1) The autofocus control device of the electronic camera controls the image pickup element 2 that picks up a subject image through the photographing lens 1, and the movement of the focus lens in the optical axis direction of the photographing lens 1 and the stop of the movement of the focus lens. A focus evaluation value is calculated using the image pickup signal from the image pickup device 2 in response to the stop of movement of the focus lens by the CPU 4 and the lens drive control circuit 10 and the lens drive mechanism 9, and the focus position is determined based on the calculated value. The CPU 4 for calculation and the first drive mode (excitation continuation flag 0) for limiting the supply power for driving the focus lens when the focus lens is stopped, or the second drive mode (excitation continuation flag 1) for limiting the supply power when the focus lens is stopped. And a CPU 4 for selecting a). Thereby, the time required for pre-excitation is shortened, and the focus adjustment time can be shortened appropriately.

(2) The autofocus control device of (1) further includes a release switch 8 capable of instructing focus adjustment and instructing imaging of a recording image, and the CPU 4 is further operated by the release switch 8. The second drive mode (excitation continuation flag 1) in which the supplied power is not limited when it is determined whether the instruction is a focus adjustment instruction or a recording image capturing instruction and the recording image capturing instruction is determined. ) Was selected. Thereby, the focus adjustment time can be shortened compared with the case where the supply power is limited.

(3) In the first drive mode corresponding to the excitation continuation flag 0, the CPU 4 and the lens drive control circuit 10 cause the focus lens to move to the first predetermined position, stop for a predetermined time, and then start to move toward the second predetermined position. In some cases, the supply power is limited during stoppage, which is effective in suppressing power consumption.

(4) The autofocus control device of (3) is effective in suppressing power consumption when the focus lens is stopped for a predetermined time after being moved to the infinity end and then moved toward the closest end.

(5) The autofocus control device of (3) is effective in suppressing power consumption when the focus lens is stopped for a predetermined time after being moved to the closest end and then moved toward the infinity end.

(6) The autofocus control device according to (3) is effective in suppressing power consumption when the focus lens is stopped for a predetermined time after being moved to the closest end or the infinity end and then moved toward the in-focus position. There is.

(Modification 1)
In the above description, an example in which excitation is turned off as the first drive mode when the excitation continuation flag is 0 has been described. You may comprise so that it may lower than a predetermined voltage (or the electric current to supply is reduced from a predetermined current). Power consumption can be suppressed compared to the case where predetermined excitation (application of a predetermined voltage or supply of a predetermined current) is continued.

(Modification 2)
In the above description, an example in which predetermined excitation (application of a predetermined voltage or supply of a predetermined current) is continued as the second drive mode when the excitation continuation flag is 1 has been described, but instead of continuing the predetermined excitation. In addition, the voltage applied to the stepping motor 9A may be lowered from a predetermined voltage (or the supplied current is reduced from the predetermined current) within a range in which the drive preparation state is maintained. Power consumption can be suppressed compared to the case where predetermined excitation (application of a predetermined voltage or supply of a predetermined current) is continued.

(Modification 3)
Even if there is an instruction to start photographing (S2 ON), if the CPU 4 determines that the remaining amount of the battery 21 is equal to or less than a predetermined value, the CPU 4 sets the excitation continuation flag to 0. Also good. When the CPU 4 sets the excitation continuation flag to 0, excitation is turned off in step S638 (FIG. 4), step S693 (FIG. 6), and step S717 (FIG. 7). Thereby, when the battery remaining amount is reduced, priority can be given to suppression of power consumption rather than shortening of the focus adjustment time.

(Modification 4)
In the above description, the case of the electronic camera 1 including the photographing lens has been described as an example. Instead, the present invention can also be applied to an interchangeable lens electronic camera system including an interchangeable lens and a camera body.

(Modification 5)
In the case of the above-described interchangeable lens camera system, when the lens driving mechanism 9 is included on the interchangeable lens side, and the CPU 4 and the lens drive control circuit 10 are included on the camera body side, the lens driving received from the CPU 4 is instructed. The control circuit 10 sends control signals such as the pre-excitation, post-excitation, drive instruction, and stop instruction described above to the stepping motor 9A constituting the lens drive mechanism 9 on the interchangeable lens barrel side.
Note that both or one of the configurations of the CPU 4 and the lens drive control circuit 10 included on the camera side may be included on the interchangeable lens side.

(Modification 6)
In the above description, after the CPU 4 turns off the excitation to the stepping motor 9A (step S722), the focusing drive process (FIG. 7) is terminated. In the case of continuous shooting, it is preferable to skip step S722 and continue excitation. Next, when executing the initial position driving process, pre-excitation (corresponding to pre-excitation (A) in FIG. 9) can be omitted to shorten the time.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

DESCRIPTION OF SYMBOLS 1 ... Shooting lens 2 ... Image pick-up element 3 ... Image signal processing circuit 4 ... CPU
DESCRIPTION OF SYMBOLS 5 ... LCD monitor 6 ... Power switch 8 ... Release switch 9 ... Lens drive mechanism 9A ... Stepping motor 10 ... Lens drive control circuit 11 ... Voltage detection circuit 12 ... Buffer memory 13 ... Non-volatile memory 21 ... Battery

Claims (10)

An image sensor that captures a subject image through an imaging optical system;
An optical system drive control unit that controls movement of the focus adjustment optical system in the optical axis direction and stop of movement of the focus adjustment optical system in the photographing optical system;
An evaluation value calculation unit that calculates a focus evaluation value using an imaging signal from the imaging element in response to the stop of movement of the focus adjustment optical system by an optical system driving unit;
A calculation unit that calculates a focus position based on a value calculated by the evaluation value calculation unit;
A selection unit that selects a first drive mode that limits a power supply for driving the focus adjustment optical system when the focus adjustment optical system is stopped or a second drive mode that does not limit the supply power when the focus adjustment optical system is stopped; ,
An autofocus control device comprising: The autofocus control device according to claim 1,
Further, it is possible to instruct focus adjustment and determine whether an operation member capable of instructing to capture a recording image and whether an operation by the operation member is a focus adjustment instruction or a recording image imaging instruction. An instruction discriminating unit for
The auto-focus control apparatus, wherein the mode switching unit selects the second drive mode when the instruction determining unit determines that the recording image is instructed to be captured. In the autofocus control device according to claim 1 or 2,
The auto-focus control device, wherein the mode selection unit selects the first drive mode when a remaining battery level is a predetermined value or less. In the autofocus control device according to any one of claims 1 to 3,
In the first drive mode, when the focus adjustment optical system is stopped for a predetermined time after being moved to the first predetermined position by the optical system drive control unit and then started to move toward the second predetermined position, An autofocus control device characterized by being in a mode for limiting power supply. In the autofocus control device according to claim 4,
The autofocus control device, wherein the first predetermined position is an infinite end, and the second predetermined position is a close end. In the autofocus control device according to claim 4,
The autofocus control device, wherein the first predetermined position is a close end and the second predetermined position is an infinite end. In the autofocus control device according to claim 4,
The autofocus control device, wherein the first predetermined position is a near end or an infinite end, and the second predetermined position is the in-focus position. In the autofocus control device according to any one of claims 1 to 7,
The autofocus control device according to claim 1, wherein the first drive mode is a mode in which the supplied power is cut off or a mode in which lower power is supplied compared to the supplied power in the second drive mode during the stop.   An autofocus camera comprising the autofocus control device according to claim 1. The autofocus camera according to claim 9, wherein
Furthermore, an optical system drive unit that is driven and controlled by the optical system drive control unit is provided,
The optical system drive unit includes a stepping motor,
The first drive mode is a mode in which the power for exciting the stepping motor is cut off or the excitation power is lower than the power for exciting the stepping motor in the second drive mode. .

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