JP2008026805A - Automatically focusing device, and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a combined AF system that if the responsiveness in a focusing control is made to meet a phase difference AF system or a TV-AF system, there is no advantage in combining with another AF system. <P>SOLUTION: The automatically focusing device includes: a first detection means to extract the high frequency components of an image signal output by an imaging means after being photoelectrically converted from an object light transmitted through an imaging optical system and to detect the focusing state; a second detection means to detect the focus through a processing different from that of the first detecting means; a recording control means to control to record the image signal obtained from the imaging means; and a control means to adjust the focus based on the detection results by the first detecting means and the second detecting means. The control means controls the focusing responsiveness so that the responsiveness after starting the image recording operation may become lower than the responsiveness before starting the operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a focus adjustment technique used for an imaging apparatus or the like.

  The so-called TV-AF method is the mainstream for autofocus control, which is a focus adjustment technique for video cameras and digital cameras. The TV-AF method controls to search for the position of the focus lens that maximizes the AF evaluation value. This AF evaluation value is obtained by detecting the sharpness of a video from a video signal obtained by photoelectrically converting a subject image by an image sensor.

  As the TV-AF AF evaluation value, a high-frequency component extracted from a video signal by a band-pass filter in a certain band is often used. When a normal subject image is taken, the AF evaluation value increases as the focal position of the focus lens approaches the focal point (in-focus position), and the point at which the level becomes maximum is the focal point.

  As another AF method, there is an internal measurement phase difference detection method often used in a single-lens reflex camera. In the phase difference detection method of internal measurement, the amount of deviation of the focal point of the photographing lens with respect to the focal point is directly obtained by detecting the amount of deviation of the signal, that is, the amount of relative positional deviation in the beam splitting direction. This signal is a signal that is divided according to the amount of light received by dividing the light beam that has passed through the exit pupil of the photographic lens into two parts, and receiving the divided light beam by a set of focus detection sensors. Accordingly, since the accumulation operation can be performed once by the focus detection sensor, a high-speed focus adjustment operation is possible.

  Next, there is an external phase difference detection method in which a focus detection sensor is provided independently of the photographing lens even with the same phase difference detection method. In the external measurement phase difference detection method, information corresponding to the subject distance is obtained by triangulation by detecting a signal shift amount, that is, a relative positional shift amount in the beam splitting direction. This signal is a signal that is output in accordance with the amount of light received by dividing the light beam received from the subject into two parts, receiving the two divided light beams by a set of focus detection sensors.

  Other AF methods using an external sensor include a method of measuring propagation velocity using an ultrasonic sensor and a method of triangulating using an infrared sensor often used for compact cameras.

An AF method has also been proposed in which the above AF methods are combined and moved to the vicinity of the focal point by, for example, an internal phase difference detection method, and then shifted to the TV-AF method to perform focus adjustment (for example, Patent Document 1). reference).
JP-A-5-64056 (page 4, FIG. 1)

  In the case of the combination AF method, when information corresponding to the subject distance such as the phase difference AF method can be obtained at high speed, the focus lens can be moved at high speed according to the information corresponding to the subject distance. On the other hand, when recording a moving image, if the focus lens is moved quickly in order to increase the responsiveness of the focus adjustment control, a motion with a sense of incongruity applied to nature is recorded.

  That is, there are relatively many shooting scenes in moving image shooting, such as when another subject crosses in front of the main subject. In this case, if the information corresponding to the subject distance, such as the phase difference AF method, is obtained at a high speed, the scene is not settled if the tracking operation is performed at a high speed. On the other hand, when information corresponding to the subject distance such as the phase difference AF method can be obtained at high speed, the crossed subject can be focused quickly if the responsiveness of the focus lens is increased. Further, when the crossing subject passes thereafter, the main subject can be focused again.

  Accordingly, in the case of the combined AF method, there is a problem that when information corresponding to the subject distance such as the phase difference AF method is obtained at high speed, it may or may not be necessary to focus at high speed accordingly. there were.

  In order to solve the above problem, the focus adjustment technique of the present invention extracts the high-frequency component of the video signal output by photoelectric conversion of the imaging means from the subject light that has passed through the imaging optical system, and detects the in-focus state. A first detection unit, a second detection unit that detects a focal point by a process different from the first detection unit, a recording control unit that controls recording of a video signal obtained from the imaging unit, And a control unit that performs focus adjustment using the first detection unit based on the detection result of the second detection unit, and the control unit determines the responsiveness of the focus adjustment by the first detection unit. Increase after starting than before starting video recording.

  Another focus adjustment technique includes: a first detection unit that extracts a high-frequency component of a video signal output by photoelectric conversion of an imaging unit from subject light that has passed through an imaging optical system; Second detection means for detecting a focal point by processing different from the first detection means, recording control means for controlling recording of a video signal obtained from the imaging means, and detection results of the second detection means And a control means for performing focus adjustment while using the first detection means, the first focus adjustment mode giving priority to responsiveness with fast driving of the focus lens, and the first focus adjustment mode. Also has a second focus adjustment mode in which the driving speed of the focus lens is slow and priority is given to stability, and a third focus adjustment mode in which focus adjustment is performed by the first detection means without using the second detection means. , The control means Depending on the regulation mode, to change the responsiveness of the focusing.

  According to the present invention, it is possible to provide a focus adjustment technique using the advantages of each AF method in the case of a combined AF method.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

<Configuration of imaging device>
FIG. 1 shows a configuration of a camera as an image pickup apparatus of the present embodiment. Reference numeral 101 denotes a fixed first lens group, 102 denotes a variable power lens for zooming, 103 denotes a stop, and 104 denotes a fixed second lens group. Reference numeral 105 denotes a focus lens (hereinafter also referred to as a focus lens) having both a function of correcting the movement of the focal plane due to zooming and a function of focusing. Reference numeral 106 denotes a CCD as an image sensor, and 107 denotes a CDS / AGC that samples the output of the CCD 106 and adjusts the gain. Reference numeral 108 denotes a camera signal processing circuit which processes an output signal from the CDS / AGC 107 into a signal corresponding to a recording device 109 described later. A recording device 109 uses a magnetic tape as a recording medium.

  A motor 110 is a drive source for moving the variable magnification lens 102. A motor 111 is a drive source for moving the focus lens 105. Reference numeral 112 denotes an AF gate that passes only signals in the region used for focus detection from the output signal of the CDS / AGC 107. Reference numeral 113 denotes an AF evaluation value processing circuit that extracts a high frequency component from a signal that has passed through the AF gate 112 and generates an AF evaluation value. Reference numeral 114 denotes a camera AF microcomputer that controls the motor 111 to drive the focus lens 105 based on the output signal of the AF evaluation value processing circuit 113 and outputs an image recording command to the recording device 109. Reference numeral 115 denotes a monitor device that displays an output signal of the camera signal processing 108 and is used by a photographer to monitor an image. A zoom switch 116 is operated when the photographer performs zooming. The camera / AF microcomputer 114 controls the zoom lens 102 and the focus lens 105 according to the operation. Reference numeral 117 denotes a switch unit that allows the user to select a focus adjustment mode. The user can select a plurality of focus adjustment modes in combination with information displayed on the monitor device 115. Reference numeral 126 denotes an external distance measuring unit of a subject distance measurement method using information corresponding to the subject distance, and may be any of an external measurement phase difference detection method, an ultrasonic sensor method, an infrared sensor method, and the like.

<Focus adjustment mode>
In this embodiment, a plurality of focus adjustment modes are provided. Then, by changing various characteristics of the AF in accordance with the operation state of each focus adjustment mode, an AF malfunction is prevented while providing comfort to the user. Therefore, first, two user selectable focus adjustment modes, A: hybrid AF mode and B: TV-AF mode, will be described. The A: hybrid AF mode and B: TV-AF mode can be selected by the user with the switch unit 117 of FIG.

  Further, when the A: hybrid AF mode is selected, the angle-of-view matching mode (A-1) and the recording after the recording start in the recording standby before the recording start of the video signal output from the CCD 106 as the imaging device. Mode (A-2). The angle of view adjustment mode (A-1) and the AF operation mode giving the highest priority to responsiveness and focus speed are automatically selected. The recording mode (A-2) gives priority to the naturalness and smoothness of the movement of the focal position, and focus adjustment control that does not give a sense of incongruity when the recorded video is reproduced, such as compatibility between the moving speed and the stability of the focal position Is realized.

  On the other hand, when the B: TV-AF mode is selected, when a certain subject has once been focused, the operation is performed with priority given to the stability for maintaining the focusing on the subject.

<Specific scene>
Next, a scene specifying method and the like will be described with reference to FIG. The table shown in FIG. 6 is an example in which shooting conditions are specified in five states. Hereinafter, taking each specific scene as an example, a scene specifying method, AF operation mode transition for each specific scene, AF method of AF operation (TV-AF method using imaging signals, or information corresponding to subject distance is used. The subject distance measurement method) will be described.

  It should be noted that the shooting situation is specified according to the change state of the information corresponding to the subject distance by the subject distance measurement method, the change state of the AF evaluation value by the TV-AF method, and the level of the AF evaluation value, and the operation method of the AF operation Then, control for optimally performing the state transition of the AF operation processing is performed. In particular, the selection of the AF operation method and the state transition (operation mode transition) compensate for the shortcomings of the TV-AF method. The disadvantages are (1) it cannot be determined whether the subject distance has changed or the pattern has changed, and (2) when the AF evaluation level is low, it cannot be determined whether the subject is a low-contrast subject or in a blurred state. is there. In parallel, control is performed to reduce the influence of parallax caused by the subject distance measurement method being external measurement. In this parallax, the viewing angle of the external distance measuring unit 126 is different from the viewing angles of the imaging lenses 101 to 105, and the distance of a subject other than the main subject is detected.

  (Specific scene 1) is a scene such as panning in which the subject distance has changed. Therefore, the focus adjustment needs to respond immediately and reach focus. The scene determination condition is that the AF evaluation value varies greatly in the TV-AF method, and information corresponding to the subject distance from the external distance measuring unit 126 varies greatly. The AF operation mode transitions to the restart operation mode. Further, in the AF method, when focus adjustment is started, focus adjustment is performed at high speed by the subject distance measurement method, and the focus is adjusted to the focal point by the TV-AF method.

  (Specific scene 2) is a scene such as a pattern change in an equidistant subject. Therefore, the focal position does not move carelessly, and it is necessary to keep the current focal position, or focus adjustment control to follow a slight change based on the current focal position. Do not move. The scene determination condition is that the AF evaluation value varies greatly in the TV-AF method, and the information corresponding to the subject distance from the external ranging unit 126 does not vary or is very small. The AF operation mode shifts to an operation mode for confirming a focal point in the vicinity of the current position of the focus lens 105. Further, in the AF method, focus adjustment is performed by the subject distance measurement method while the AF evaluation value is fluctuating, and focus adjustment is performed by the TV-AF method when the AF evaluation value is stabilized. As described above, the focus position is also maintained during the focus adjustment by the subject distance measurement method.

  (Specific scene 3) is a scene in which parallax between the photographing lenses 101 to 105 and the external distance measuring unit 126 occurs. Therefore, the focus adjustment is performed using the AF evaluation value of the TV-AF method without using information corresponding to the subject distance of the external subject distance measurement method with low reliability. The scene determination condition is that the AF evaluation value in the TV-AF method is not changed, the level of the AF evaluation value is high, and the information corresponding to the subject distance in the subject distance measurement method is greatly changed. The AF operation mode transitions to the restart operation mode. Further, the AF method performs focus adjustment by the TV-AF method.

  (Specific scene 4) is a scene such as panning in which the subject distance of a subject with low contrast has changed. Therefore, it is necessary to increase the responsiveness of the focus adjustment to reach the focal point. On the other hand, in the TV-AF method, the mountain shape of the AF evaluation value corresponding to the position of the focus lens 105 cannot be obtained. Therefore, the in-focus point cannot be captured, and a hunting state in which the focus lens compensator 105 is scanned to the closest side infinite side is obtained. The scene determination condition is that the AF evaluation value does not vary according to the TV-AF method, the level of the AF evaluation value is low, and the information regarding the subject distance of the subject distance measurement method varies greatly. The AF operation mode transitions to the restart operation mode. Further, in the AF method, focus adjustment is performed by the subject distance measurement method, and when the level of the AF evaluation value of the TV-AF method becomes high, the in-focus point is confirmed by the TV-AF method.

  (Specific scene 5) is a fixed scene such as a tripod in a state where there is no change in subject distance and no change in pattern. Therefore, the focus position needs to hold the current focus position. The scene determination condition is that there is no change in the AF evaluation value of the TV-AF method, and there is no change in information corresponding to the subject distance of the subject distance measurement method. The AF operation mode transitions to an operation mode that maintains the current position of the focus lens 105. As a result, a so-called AF lock state is established, and it is not necessary to select the AF method until the next change in the shooting situation.

<AF control>
Next, AF control performed by the camera AF microcomputer 114 will be described with reference to FIG. The flowchart of FIG. 3 is an example in which the five representative shooting scenes shown in FIG. 6 are identified and the control state of the AF operation is changed. Unless otherwise specified, the process is performed according to instructions from the camera AF microcomputer 114.

  Step 301 indicates the start of processing. First, in Step 330, the current focus adjustment mode based on the user's operation is taken in, and the above modes A (A-1, A-2) and B are discriminated. Next, at Step 322, it is selected whether the main signal is the TV-AF method signal or the subject distance measurement method signal as the AF operation. If it is the TV-AF system, the process proceeds to Step 302, and if it is the subject distance measurement system, the process proceeds to Step 323. Here, in the initial state when the power is turned on, focus adjustment is performed according to information corresponding to the subject distance of the subject distance measurement method. That is, when the focus adjustment mode is selected as B: TV-AF mode, the process proceeds to Step 302, and when the focus adjustment mode is selected as A: Hybrid AF mode, the process proceeds to Step 323.

  In the case where the processing routine described later is advanced and TVAF is selected in Step 329 and the process returns to Step 322 again, the process proceeds to Step 302 even if the focus adjustment mode is the A: hybrid AF mode.

  When performing the focus adjustment by the TV-AF method, a minute driving operation is performed at Step 302, and it is determined whether the in-focus position is in focus or not in focus. How to change the operation characteristics of the minute driving operation according to the focus adjustment mode of this embodiment will be described later.

In Step 305, it is determined whether or not the focus is determined in Step 302. If the focus is determined, the process proceeds to Step 311 to perform the focus / restart determination process. If the focus is not determined, the process proceeds to Step 306.
In Step 306, it is determined whether or not the direction can be determined in Step 302. If the direction can be determined, go to Step 307 to perform a hill-climbing drive operation. If the direction cannot be determined, return to Step 302 via Step 322 and continue the minute drive operation. .

  In Step 307, the focus lens is driven to climb up at a predetermined speed. How to change the operation characteristics of the hill-climbing operation according to the focus adjustment mode of this embodiment will be described later.

  In Step 308, it is determined whether or not the AF evaluation value exceeds the peak in the step 307 hill-climbing drive. If it is determined that the peak has been exceeded, the process proceeds to Step 309. In Step 309, the focus lens 105 is returned to the position where the AF evaluation value during the hill-climbing driving operation becomes a peak. In Step 310, it is determined whether or not the focus lens 105 has returned to the position where the AF evaluation value is the peak. As a result, when it returns to the peak, it returns to Step 302 via Step 322 and performs the minute driving operation again. On the other hand, if it has not returned to the peak, the operation returns to Step 309 to return to the peak.

  Next, focus / restart determination processing from Step 311 will be described. In Step 311, the focus lens 105 is moved to the focus position determined to be in focus. In Step 312, it is determined whether or not the focus position has been moved. If it has moved to in-focus transfer, it will progress to Step 313, and if it has not moved, it will return to Step 311. In Step 313, information corresponding to the AF evaluation value at the in-focus position and the subject distance of the subject distance measurement method is held. In step 314, the latest AF evaluation value and information corresponding to the subject distance of the subject distance measurement method are fetched. In step 317, it is determined whether or not the amount of change in information corresponding to the subject distance of the subject distance measurement method of the external distance measuring unit 216 is large. When the variation amount is large, in Step 315, the AF evaluation value held in Step 313 is compared with the latest AF evaluation value to determine whether the variation of the AF evaluation value is large. If the AF evaluation value fluctuates greatly, the process proceeds to Step 319, and the next AF operation is set as a subject distance measurement method in which information corresponding to the subject distance is used. Returning to Step 322, the process proceeds from Step 323 to the restart operation mode. This is the processing specified as the shooting situation of the specific scene 1. If it is determined in Step 315 that the AF evaluation value has not fluctuated, the process goes to Step 318 to determine whether the level of the current AF evaluation value captured in Step 314 is less than a predetermined threshold value. When the level of the AF evaluation value is low, the flow advances to Step 319 as a subject distance change scene to a subject with low contrast in the specific scene 4. And it changes to restart operation mode. When the level of the AF evaluation value is equal to or greater than the predetermined threshold, it is determined that the parallax of the external measurement unit 126 in the specific scene 3 has occurred, and it is determined in Step 320 that the next AF operation is also performed by TVAF. From Step 322, the process returns to Step 302 and transitions to the restart operation mode.

  If it is determined in step 317 that the information corresponding to the subject distance of the external distance measuring unit 126 has not changed, the process proceeds to step 321. Then, the AF evaluation value held in Step 313 is compared with the latest AF evaluation value, and it is determined whether the variation of the AF evaluation value is large. If the AF evaluation value has fluctuated greatly, the process proceeds to Step 319, the next AF operation is set as the subject distance measurement method, the process returns to Step 322, and the process proceeds from Step 323 to the operation mode. However, since the information corresponding to the subject distance is not changed at this time, the position of the focus lens 105 is controlled to be substantially maintained. This shooting situation corresponds to a case where an equidistant subject in the specific scene 2 is panned. Therefore, although there is no distance change, it is specified that the AF evaluation value fluctuates due to a change in the pattern of the captured image. When it is determined in Step 321 that there is no change in the AF evaluation value, in Step 316, the focus lens 105 is stopped, and the process returns to Step 314 to continue the focus / restart determination process. This shooting scene is the state of the specific scene 5 in which there is no change in the distance of the subject and the pattern.

  When returning to the processing from Step 322 via Step 319, there are cases of specific scenes 1, 2, and 4. In Step 330, A: hybrid AF mode is determined, and in Step 322, the subject distance measurement method is determined. Proceeding to step 323, the focus compensator 105 is moved while the AF evaluation value of TVAF is captured. This moving position is the in-focus position calculated based on the distance information while capturing the latest external ranging information in Step 324. During the process of Step 324, the moving speed of the focus lens 105 and the acceleration / deceleration characteristics of the moving speed are changed according to the state of the focus adjustment mode captured in Step 330. The characteristic change will be described later. In Step 325, it is monitored whether the focus position has reached the in-focus position measured by the subject distance measurement method. If not, the process returns to Step 323 and waits for arrival.

  In the case of the specific scene 1, since there is a certain change in the distance of the subject, the focus position is adjusted at high speed to the in-focus position in the subject distance measurement method as a restart operation. In the case of the specific scene 2, since there is no change in the distance, the focus position in the subject distance measurement method operates so as to substantially hold the position of the focus lens 105 determined in Step 321. When the contrast of the subject in the specific scene 4 is low, there is a change in distance, so that immediate focus adjustment is performed.

  When the position of the focus lens 105 reaches a position corresponding to the focal point in the subject distance measurement method, the AF evaluation value is captured again at Step 326. In Step 327, it is determined whether or not the variation amount of the AF evaluation value is large. When the AF evaluation value fluctuates greatly, the pattern of the equidistant subject in the specific scene 2 is changing. Therefore, in order to maintain the current focus position, the process returns to Step 323 and the focus adjustment according to the information corresponding to the subject distance in the subject distance measurement method is continued. When the camera work is stabilized and the fluctuation of the AF evaluation value is settled, the process reaches Step 329 via Step 328, and the operation shifts to the focus confirmation operation by TV-AF from the next time. Step 328 determines whether the level of the current AF evaluation value is less than a predetermined threshold value. When the AF evaluation value level is low, it is determined that the scene is a specific scene 4 with low contrast of the subject, and the process returns to Step 323 without shifting to TV-AF, and the focusing operation according to the external distance measurement information is continued. When the subject is changed to a subject with high contrast, the AF evaluation value exceeds a predetermined threshold value in Step 328. Therefore, the AF operation is switched to the TV-AF method at Step 329, the process returns to Step 322, and the operation shifts to the focus confirmation operation by TV-AF.

<Micro drive>
Next, the minute driving operation will be described with reference to FIG. Step 401 indicates the start of processing. In Step 402, it is determined whether or not the current Mode is 0. If it is 0, the process proceeds to Step 403, and the process at the lens position on the near side described later is performed.

(Processing at the closest lens position)
In Step 403, an AF evaluation value is fetched from the AF evaluation value processing circuit. This AF evaluation value is based on a video signal generated from charges accumulated in the CCD when Mode = 2 described later and the focus lens 105 is on the infinity side. In Step 404, the AF evaluation value captured in Step 403 is stored as an infinite side AF evaluation value. In Step 405, if the direction determined to be the in-focus direction is the same one predetermined number of times, the process proceeds to Step 408. If the direction determined to be the in-focus direction for a predetermined number of times 1 is not the same, the process proceeds to Step 406. In Step 406, the average position of the focus lens 105 in the predetermined period so far is calculated as the focal point. In Step 407, if the two-focus lens 105 repeats reciprocation in the same area a predetermined number of times, the process proceeds to Step 409. If the focus lens 105 does not repeat reciprocation within the same area a predetermined number of times, the process proceeds to Step 410, Mode is added, and the process proceeds to Step 411 to exit the present process. The addition here returns to 0 when 4 or more, and the cyclic counter values of 0, 1, 2, and 3 are determined.

  In Step 408, assuming that the direction can be determined, the process proceeds to Step 411 and the process is terminated. In Step 409, it is determined that the in-focus state has been determined.

  In Step 412, it is determined whether or not the current Mode is 1, and if it is 1, the process proceeds to Step 413, and a process for driving the lens described below infinitely is performed. Otherwise, the process proceeds to Step 418.

(Process to drive the lens indefinitely)
In Step 413, the vibration amplitude and the center movement amplitude are calculated. Although not described in detail here, based on the depth of focus, it is common to decrease the amplitude when the depth is shallow and increase the amplitude when the depth is deep. In Step 414, the infinite AF evaluation value at Mode = 0 is compared with the near-side AF evaluation value at Mode = 3, which will be described later. If the infinite AF evaluation value is larger than the closest AF evaluation value, the process proceeds to Step 415. On the other hand, if the infinite AF evaluation value is smaller than the closest AF evaluation value, the process proceeds to Step 416.

  In Step 415, the drive amplitude is (drive amplitude) = (vibration amplitude) + (center movement amplitude). In Step 416, the drive amplitude is (drive amplitude) = (vibration amplitude). In Step 417, driving is performed in the infinite direction with the amplitude determined in Step 415 or Step 416. Step 405 and subsequent steps are as described above.

  In Step 418, it is determined whether or not the current Mode is 2. If it is 2, the process proceeds to Step 419, and the process at an infinite lens position described later is performed, otherwise, the process proceeds to Step 421.

(Processing at infinite lens position)
In Step 419, an AF evaluation value is fetched from the AF evaluation value processing circuit. This AF evaluation value is based on a video signal generated from charges accumulated in a CCD as an image sensor when Mode = 0 described above and the focus lens 105 is on the near side. In Step 420, the AF evaluation value captured in Step 419 is stored as the closest AF evaluation value. Step 405 and subsequent steps are as described above.

(Process to drive the lens closer)
In Step 421, the vibration amplitude and the center movement amplitude are calculated. Although not described in detail here, the amplitude is generally small when the depth is shallow and the amplitude is large when the depth is deep, based on the subject depth. In Step 422, the infinite AF evaluation value at Mode = 0 is compared with the near AF evaluation value at Mode = 3. If the close AF evaluation value is larger than the infinite AF evaluation value, the process proceeds to Step 423. On the other hand, if the closest AF evaluation value is smaller than the infinite AF evaluation value, the process proceeds to Step 424.

  In Step 423, the drive amplitude is (drive amplitude) = (vibration amplitude) + (center movement amplitude).

  In Step 424, the drive amplitude is (drive amplitude) = (vibration amplitude).

  In Step 425, driving is performed in the infinite direction with the amplitude determined in Step 423 or Step 424. Step 405 and subsequent steps are as described above.

FIG. 5 shows the time course of the operation of the focus lens 105. Here, the horizontal axis represents time, and the vertical axis represents the position of the focus lens 105. The downwardly convex period at the top represents the vertical synchronization signal of the video signal. Here, the AF evaluation value EV _A for the electric charge (hatched ellipse) accumulated in the CCD as the image sensor during _A is taken in at time T _A. The AF evaluation value EV _B for the charge (hatched ellipse) accumulated in the CCD during _B is taken in at time T _B. At time _{T C,} AF evaluation values _EV A, compares the EV _B, to move the vibration center if EV B> EV _A. On the other hand, if EV _A > EV _B , the vibration center is not moved.

<Mountain climbing action>
Next, the hill-climbing driving operation will be described with reference to FIG. Step 601 indicates the start of processing. In Step 602, an AF evaluation value is fetched from the AF evaluation value processing circuit. In Step 603, the hill-climbing driving speed is set. Although not described in detail here, based on the subject depth, it is common to decrease the speed when the depth is shallow and increase the speed when the depth is deep. In Step 604, it is determined whether or not the AF evaluation value captured in Step 602 is smaller by a predetermined amount than the previous AF evaluation value. If not smaller, the process proceeds to Step 605, and if smaller, the process proceeds to Step 611. Here, the predetermined amount is a value determined in consideration of the S / N of the AF evaluation value, and is a value equal to or larger than the fluctuation range of the AF evaluation value when the subject is fixed and the focus lens is constant. Otherwise, hill-climbing cannot be driven in the correct direction due to the influence of the fluctuation of the AF evaluation value. In Step 605, it is determined whether or not the focus lens 105 has reached the infinite end. The infinite end is the position closest to the end of the stroke of the focus lens 105 determined by design. If it has reached the infinite end, the process proceeds to Step 609. If not, the process proceeds to Step 606. In Step 606, it is determined whether or not the focus lens 105 has reached the closest end. The closest end is a position closest to the stroke of the focus lens 105 determined by design. If the close end has been reached, go to Step 610. If not, the process proceeds to Step 607. In Steps 609 and 610, a flag for storing the inverted end is set, and the process proceeds to Step 613. The focus lens 105 is inverted in the reverse direction and the hill-climbing driving is continued. In Step 607, the focus lens 105 is hill-climbed and driven at a predetermined speed in the previous forward direction, and the process proceeds to Step 608 to end the current process.

  In Step 611, if the AF evaluation value has not decreased beyond the peak, the process proceeds to Step 612. On the other hand, if the AF evaluation value has decreased beyond the peak, the process proceeds to Step 614 to end the hill-climbing drive, and the process proceeds to Step 608 to complete the process and shift to the minute drive operation. In Step 612, it is determined whether or not it has been continuously reduced by the predetermined number of times 3, and if it has been continuously reduced, the process proceeds to Step 613. On the other hand, if it does not decrease continuously, the process proceeds to Step 607. In Step 607, the focus lens 105 is hill-climbed and driven at a predetermined speed in the previous forward direction, and the process proceeds to Step 608 to end the current process. In Step 613, the focus lens 105 is hill-climbed and driven at a predetermined constant speed in the direction opposite to the previous time, and the process proceeds to Step 608 to end the current process.

  FIG. 7 shows the movement of the lens during the hill-climbing driving operation. Here, since A decreases beyond the peak, it is determined that there is a focal point, and the hill-climbing driving operation is terminated, and the operation shifts to the minute driving operation. On the other hand, since B decreases with no peak, it is reversed as having the wrong direction, and the hill-climbing driving operation is continued.

<Speed change control of focus lens 105>
Next, how to control the characteristics of the TV-AF method and the subject distance measurement method in accordance with the focus adjustment mode will be described. When the user selects the A: hybrid AF mode, at Step 330 in FIG. 3, it is determined whether the current view angle alignment mode (A-1) or recording mode (A-2) is in the recording standby mode. Determine. In the angle-of-view adjustment mode, the external distance measuring unit 126 sets the moving speed X of the focus lens 105. On the other hand, in the recording mode (A-2), the moving speed Y of the focus lens 105 is set. Here, X> Y. Specifically, it is a high-speed movement of about X = 60 mm / sec, and if the focus stroke is 1 mm, the movement can be completed within one vertical synchronization period. The speed Y is a speed of about 10 mm / sec, and is set so that the focus movement is not too slow and the focus is smoothly adjusted until the focus is reached. Further, when moving at a speed B, a predetermined time passes through an acceleration pattern of 2.5 mm / sec → 5 mm / sec → 10 mm / sec. Further, a deceleration pattern opposite to the acceleration pattern is stepped on for a predetermined time before reaching the in-focus position in the subject distance measurement method. This enables natural focusing so that the in-focus position can be reached smoothly.

<TV-AF operation>
Next, the TV-AF operation when the A: hybrid AF mode is selected or the B: TV-AF mode is selected, the characteristics are changed in Steps 302 and 306.

  In Step 302 of FIG. 3, the characteristics of the minute driving operation are changed. The change variables are the minute drive amplitude and the ease of determining the direction (ease of shifting to the hill-climbing operation). Specifically, the drive amplitude of the minute drive operation calculated in Steps 413 and 421 in FIG. This is a condition of “whether the in-focus direction is the same for a predetermined number of times 1” determined in Step 405. The focus drive mode is set from large to small in the order of the angle-of-view adjustment mode (A-1), the recording mode (A-2), and the B: TV-AF mode. In addition, the condition for ease of direction determination is set as sweet → severe. Specifically, the predetermined number 1 is small → large. In the angle-of-view adjustment mode in which the drive amplitude is large and the direction determination condition is not large, the drive amount per time is large. In addition, since the predetermined number of times 1 is small, the in-focus direction can be determined early, and the next hill-climbing operation can be immediately performed, thereby improving the responsiveness.

  On the other hand, the TV-AF mode is a stability priority mode. When it is determined that the in-focus direction has been detected while setting the movement of the minute amplitude operation to be invisible on the screen, the hill-climbing operation is started. This also makes the transition conditions stricter. This is to prevent a change in the focal position from occurring on the screen by shifting to a hill-climbing operation under the condition that there is no distance change when an object enters and exits near the focal point. This is because by making the hill-climbing transition conditions strict, the focus position slowly vibrates in the vicinity of the in-focus point and in the range where the blur cannot be seen, so that the visual focus can be maintained. On the other hand, in the case of the recording mode (A-2), an intermediate value (intermediate condition) between the angle-of-view adjustment mode and the TV-AF mode is determined so that a good balance between responsiveness and stability can be obtained. The

  In Step 306, the driving speed of the mountain climbing operation is determined according to the focus adjustment mode. Specifically, it is determined in Step 603 of FIG. In accordance with the purpose of the focus adjustment mode described above, the hill-climbing speed is set from large to small in the order of the angle-of-view adjustment mode (A-1), recording mode (A-2), and B: TV-AF mode. This is to increase the responsiveness in the angle-of-view mode (A-1), and since stability is a priority in the TV-AF mode, even if a mountain climbing operation is mistakenly performed, the responsiveness is lowered by reducing the speed at which blurring is difficult to understand. .

  FIG. 10 shows a list of the features of this embodiment described above. It shows how the speed in the subject distance measurement method, TV-AF method, and other characteristic determination parameters are set according to each focus adjustment mode to realize the basic operation in each mode.

  In this embodiment, when the user selects the B: TV-AF mode as the focus adjustment mode, the stability is adjusted so that the focus does not fluctuate due to the entry / exit of the subject from the focus adjusted once such as tripod shooting. It was expensive. In this regard, when the conversion lens is attached, the B: TV-AF mode may be set. This is to prevent the phenomenon that the photographed image is out of focus even if the focus lens 105 is moved to a position corresponding to the measured subject distance. This phenomenon occurs because the optical path lengths of the imaging lenses 101 to 105 and the external distance measuring unit 126 are different even when the subject is equidistant when a conversion lens or the like is attached.

  As described above, the optimum AF operation can be performed according to the shooting state. In particular, the responsiveness is given priority when adjusting the angle of view, and the AF characteristics are changed so as to balance responsiveness and stability during recording. This makes it possible to provide a comfortable focus adjustment function that matches the purpose of the shooting situation. In particular, since focus adjustment has high user preference, focusing that matches the user preference can be realized by allowing the user to select the focus adjustment. At the same time, it is possible to provide a comfortable feeling.

  Furthermore, even when the distance detection accuracy is poor, it is possible to improve the response with only the TV-AF in the angle-of-view matching with the response priority, and it is possible to provide comfort in any shooting scene. This is because, in the focus adjustment mode, not only the AF means other than the TV-AF that detects the subject distance and calculates the focus position, but also the operation characteristics of the TV-AF are changed so as to match the focus adjustment mode that operates.

<Others>
FIG. 2 is a diagram showing a system configuration of an imaging apparatus that is partially different from FIG. A description of the same components as in FIG. 1 is omitted. Although the external distance measuring unit 126 is used in FIG. 1, the TTL phase difference detection method is used in FIG. Reference numeral 131 denotes a fixed first fixed lens group, 132 denotes a variable power lens group that performs zooming, 133 denotes a focus lens, and 120 denotes an imaging lens. Reference numeral 121 denotes a half prism that performs light division for autofocus. Reference numeral 122 denotes a sub mirror, and 123 denotes an imaging lens for AF. Reference numeral 124 denotes a phase difference detection type AF sensor, and 125 denotes an AF circuit. The AF microcomputer 114 detects a shift amount and a shift direction from the output of the AF sensor 124 via the AF circuit 125.

  In the case of the imaging apparatus having such a configuration, the diaphragm 103 is actually in operation during moving image shooting. Therefore, it is necessary to divide the input light by the half prism 121 before the diaphragm 103.

  The above-described AF control algorithm can also be applied to the configuration described with reference to FIG. FIG. 4 shows a flowchart of the configuration described in FIG. Since this flowchart corresponds to FIG. 3, the description of the common parts will be left here. What is different is that Step 401, Step 402, Step 403, Step 404, Step 405, and Step 406 are changed to internal measurement distance measurement information.

It is a figure which shows the structure of the camera of an Example. It is a figure which shows the structure of another camera. It is a flowchart explaining AF control. It is a flowchart explaining another AF control. FIG. 6 is a diagram showing a time course of operation of the focus compensator 105. It is a figure explaining the relationship between the output change of the external measurement sensor in each imaging | photography condition, and the output change of an internal measurement sensor. It is the figure which showed the movement of the lens at the time of hill-climbing drive operation | movement. It is a flowchart explaining a micro drive. It is a flowchart explaining a mountain climbing operation | movement. It is a figure explaining a characteristic determination parameter.

Explanation of symbols

105 Focus lens (focus lens)
106 CCD as an image sensor
DESCRIPTION OF SYMBOLS 109 Recording apparatus 110 Motor which is a drive source for moving the variable power lens 102 111 Motor which is a drive source for moving the focus lens 105 113 AF evaluation value processing circuit 114 Camera AF microcomputer 117 Focus adjustment mode user Selectable switch unit 126 External distance measuring unit

Claims (13)

First detection means for extracting a high-frequency component of a video signal output by photoelectric conversion of the imaging means from subject light that has passed through the imaging optical system, and detecting a focused state;
Second detection means for detecting a focal point by a process different from that of the first detection means;
Recording control means for controlling recording of the video signal obtained from the imaging means;
Control means for performing focus adjustment using the first detection means based on the detection result of the second detection means,
The focus adjustment apparatus characterized in that the control means increases the responsiveness of the focus adjustment by the first detection means after the start of the video recording than before the start of the video recording.   A first mode using the detection results of the first detection means and the second detection means, and a second mode using the results of the second detection means without using the results of the first detection means; And the control means lowers the responsiveness of focus adjustment after the start in the first mode than in the start of the video recording, and the video in the second mode. 2. The focus adjustment apparatus according to claim 1, wherein the responsiveness of the focus adjustment is not changed before and after the start of recording.   3. The control unit according to claim 1, wherein the control unit uses the detection result of the first detection unit after using the detection result of the second detection unit to approach a substantially in-focus position. 4. Focusing device.   4. The control special means increases the responsiveness by increasing the moving speed for moving the focal position using the detection result of the second detection means. The focus adjustment device described in 1.   5. The control characteristic changing unit according to claim 1, wherein the control characteristic changing unit changes acceleration / deceleration of a moving speed when the focal position is moved using the detection result of the second detecting unit before and after starting the video recording. The focus adjustment apparatus according to any one of the above.   The control means uses the detection result of the first detection means to reduce the moving speed for moving the focal position in the direction in which the high-frequency component of the video signal increases to be lower after the start than before the start of the video recording. The focus adjustment device according to claim 1, wherein the focus adjustment device is a feature.   2. The control characteristic changing unit narrows a moving amplitude when moving a focal position using a detection result of the second detecting unit after starting than before starting the video recording. The focus adjustment apparatus according to any one of 1 to 6.   The control characteristic changing means makes it difficult to shift from minute drive control to hill climbing drive control using the detection result of the second detection means after the start than before the start of the video recording. The focus adjustment apparatus according to any one of claims 1 to 7.   The focus adjustment apparatus according to claim 1, wherein a photographer can select the first mode and the second mode.   9. The focus adjustment apparatus according to claim 1, wherein the video recording is a video recording of a moving image. First detection means for extracting a high-frequency component of a video signal output by photoelectric conversion of the imaging means from subject light that has passed through the imaging optical system, and detecting a focused state;
Second detection means for detecting a focal point by a process different from that of the first detection means;
Recording control means for controlling recording of the video signal obtained from the imaging means;
A control means for performing focus adjustment while using the first detection means based on the detection result of the second detection means, and a first focus adjustment mode in which priority is given to fast response of the focus lens, The second focus adjustment mode in which the driving speed of the focus lens is slower than the first focus adjustment mode and prioritizes stability, and the first detection unit performs focus adjustment without using the second detection unit. 3. The focus adjustment apparatus according to claim 3, wherein the control means changes the responsiveness of the focus adjustment in accordance with the focus adjustment mode state.   The focus adjustment apparatus according to claim 1, wherein the second detection unit measures a subject distance. An imaging apparatus comprising: an imaging element; and the focus adjustment apparatus according to any one of claims 1 to 12.

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