JP2008052191A - Focusing device and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focusing device that can perform accurate focusing. <P>SOLUTION: The focusing device includes: a lens driving means for driving a focusing lens; a first focusing means for searching for a focusing position while driving the lens by the lens driving means to perform the focusing of the lens; a second focusing means for driving a lens by the lens driving means by a focusing method different from the first focusing means to perform the focusing; a controlling means for performing the focusing with the first focusing means after driving the lens with the lens driving means by an initial driving amount (e.g. step wide×2-amount of backlash) from the lens position where the focusing by the second focusing means is finished; and an initial driving amount determining means for determining the initial driving amount according to driving performance of the lens driving means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  A hybrid AF that combines phase difference detection autofocus (hereinafter referred to as AF) and contrast detection AF is provided, and -5Fδ (F; focus adjustment lens) is once on the front pin side from the focus position of the phase difference detection AF. The maximum aperture value, δ (minimum resolution of the imaging diameter), and the contrast detection method AF is performed while driving the focusing lens on the rear pin side by Fδ / 2 from that position to the position of + 5Fδ, and the maximum contrast evaluation value There is known a focus adjustment device that drives a focus adjustment lens to a position (for example, see Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2005-092085 A

  However, in the conventional focus adjustment apparatus described above, the lens drive direction is reversed so as to drive the lens to the start position of the contrast detection method AF, so that accurate focus adjustment cannot be performed due to the backlash of the lens drive mechanism. There's a problem.

(1) The invention of claim 1 includes a lens driving unit that drives the focus adjustment lens, a first focus adjustment unit that searches for a focus position while driving the lens by the lens driving unit, and performs focus adjustment of the lens, The second focus adjusting means for adjusting the focus by driving the lens by the lens driving means with a focus adjustment method different from the first focus adjusting means, and the lens at the time when the focus adjustment by the second focus adjusting means is completed. From the position, after the lens is driven by the initial driving amount by the lens driving means, the control means for performing the focus adjustment by the first focus adjustment, and the initial driving amount determination for determining the initial driving amount according to the driving characteristics of the lens driving means Means.
(2) In the focus adjusting apparatus according to the second aspect, the initial driving amount is determined by the initial driving amount determining unit according to the type of the lens driving unit.
(3) In the focus adjustment apparatus according to the third aspect, the initial drive amount is determined by the initial drive amount determination means in accordance with the amount of play of the lens drive means.
(4) In the focus adjusting apparatus according to claim 4, the first focus adjusting means is a contrast detecting focus adjusting means, and the second focus adjusting means is a phase difference detecting focus adjusting means.
(5) The invention of claim 5 is a camera including the focus adjusting apparatus according to any one of claims 1 to 4.

  According to the present invention, accurate focus adjustment is possible.

  An embodiment in which the present invention is applied to a digital single-lens reflex camera provided with a hybrid AF of phase difference detection AF and contrast detection AF will be described. The present invention is not limited to a digital single-lens reflex camera, and can be applied to all types of cameras provided with a hybrid focus adjustment device. Further, the present invention is not limited to the hybrid AF of the phase difference detection AF and the contrast detection AF, and can be applied to a hybrid AF combining all types of AF.

<< First Embodiment of the Invention >>
FIG. 1 shows a configuration of a digital single-lens reflex camera provided with the focus adjustment apparatus of the first embodiment. This camera focus adjustment device is a hybrid AF of a phase difference detection AF and a contrast detection AF. In the camera of one embodiment, a lens barrel 200 is attached to the camera body 10. In this embodiment, an interchangeable lens camera will be described as an example. However, the present invention is not limited to the interchangeable lens camera, and can be applied to a fixed lens camera.

  The camera body 10 includes an image sensor 20, finder constituent members 25 to 60, a quick return mirror 70, a mirror up switch 75, a sub mirror 80, a fixed mirror 90, a phase difference detection AF detection device 100, a defocus amount calculation unit 300, a lens. A drive amount setting unit 310, a focus evaluation value calculation unit 320, a lens type determination unit 330, and the like are provided. The image sensor 20 converts an image formed by the lens into an electrical signal and outputs the electrical signal. Although illustration is omitted, an infrared cut filter for cutting infrared light and an optical low-pass filter for preventing aliasing noise of an image are arranged on the front surface of the image pickup surface of the image pickup device 20.

  The finder portion of the camera body 10 includes a focusing screen 25, a pentaprism 30, a photometric element 40, a relay lens 50, an eyepiece 60, and the like. The photometric element 40 measures the brightness of the image and outputs a photometric value for determining the shutter speed and aperture value.

  As shown in the figure, the quick return mirror 70 is set in a photographing optical path that guides subject light that has passed through a lens optical system 210 (to be described later) to the image sensor 20 before exposure. 10 to the pentaprism 30 arranged above 10. On the other hand, at the time of exposure, it jumps up to the lower side of the focusing screen 25 and guides subject light from the lens optical system 210 to the image sensor 20. Further, the vicinity of the center of the quick return mirror 70 is a half mirror, and a part of the subject light is transmitted through the half mirror portion and guided to the phase difference detection AF detection element 100 through the sub mirror 80 and the fixed mirror 90. . The mirror up switch 75 is a switch that is turned on when the quick return mirror 70 is retracted from the photographing optical path.

  The phase difference detection AF detection element 100 divides subject light from the lens optical system 210 into two by a mask, and then re-images it on two line sensors. The shift amount of the re-imaged images on the two line sensors corresponds to the focus shift amount (defocus amount). The output of the phase difference detection AF detection element 100 is sent to the defocus amount calculation unit 300.

  The lens barrel 200 includes a lens optical system 210, a zoom encoder 220, a distance encoder 230, a focusing (focus adjustment) lens drive motor 240, a diaphragm 250, and the like.

  The lens optical system 210 is an optical system for forming a subject image on the imaging surface of the image sensor 20. The zooming (focal length adjustment) lens 210b is configured to be movable in the direction of the optical axis, and the position of the zooming lens 210b usually changes when the photographer turns the zoom ring (not shown) of the lens barrel 200. Accordingly, the focal length of the entire lens optical system 210 changes. The position of the zooming lens 210b is monitored by the zoom encoder 220.

  The focusing (focus adjustment) lens 210c is configured to be movable in the optical axis direction, and is driven by the focusing lens driving motor 240 in accordance with the lens driving signal calculated by the lens driving amount setting unit 310 of the camera body 10. The position of the focusing lens 210c is monitored by the distance encoder 230 and sent to the lens driving amount setting unit 310 as distance information. This distance is equivalent to the distance from the imaging surface of the image sensor 20 to the subject in focus.

  The diaphragm 250 is an aperture diaphragm that adjusts the amount of subject light that reaches the image sensor 20. The diaphragm 250 may be set automatically by the camera or manually by the photographer. In the case of the program mode or the shutter speed priority mode, the aperture value is determined from the output of the photometric element 40 or the like. In the aperture priority mode or manual mode, the photographer sets. The diaphragm 250 is driven by a diaphragm drive motor (not shown) or the like according to a value set by a camera or a photographer.

  The defocus amount calculation unit 300, the lens drive amount setting unit 310, the focus evaluation value calculation unit 320, and the lens type determination unit 330 are each composed of peripheral components such as a microcomputer and a memory. The defocus amount calculation unit 300 calculates a defocus amount that represents a focus shift amount based on the output of the phase difference detection AF detection element 100.

  The lens drive amount setting unit 310 sets the drive amount of the focus adjustment lens based on the calculation result of the defocus amount and the focus evaluation value. In the phase difference detection method AF, a value obtained by subtracting the current lens position from the position where the defocus amount = 0 is set as the lens driving amount. The current lens position is the position detected by the distance encoder 230. On the other hand, in the contrast detection method AF, the focusing lens 210c is driven by a predetermined amount (hereinafter referred to as “step amount” or “step width”) to calculate a focus evaluation value, and a position where the focus evaluation value is maximized is determined as the in-focus position. And Accordingly, the step amount is set as the driving amount until the in-focus position is found, and when the in-focus position is found, the position where the focus evaluation value is maximum, that is, the value obtained by subtracting the current lens position from the in-focus position is set as the lens driving amount.

  Although details will be described later, in the first embodiment, the focus adjustment of the focusing lens 210c is performed by the phase difference detection method AF, and from the position of the focusing lens 210c when the focus adjustment by the phase difference detection method AF is completed, After the focusing lens 210c is driven by the “initial driving amount” by the focusing lens driving motor 240, the focus is adjusted by contrast detection AF. The initial driving amount is the focusing lens from the focus position of the phase difference detection AF (hereinafter referred to as the detection focus position) to the position where the contrast detection AF is started when switching from the phase difference detection AF to the contrast detection AF. This is the amount by which the position of 210c is shifted, and the initial drive amount is determined according to the drive characteristics of the drive mechanism of the focusing lens 210c.

  The driving characteristics of the driving mechanism of the focusing lens 210c differ depending on the type of the lens optical system 210 built in the lens barrel 200. Therefore, the lens type signal is input from the lens type determination unit 330, and the driving characteristic corresponding to the lens type signal is read from the driving characteristic map of the driving mechanism corresponding to the lens type stored in advance. The drive characteristics of the drive mechanism include the amount of play of the drive mechanism or the amount of play itself.

  The focus evaluation value calculation unit 320 calculates a focus evaluation value of a portion corresponding to a partial region (= ranging area) in the image output of the image sensor 20. Specifically, the focus evaluation value is calculated while gradually moving the focus adjustment lens 210b, and the position where the focus evaluation value is maximized is set as the in-focus position. The method for calculating the focus evaluation value is generally a method in which high-frequency emphasis filter processing is performed on an image and the results are integrated. However, the method is not particularly limited to this method, and various methods can be adopted. .

  The lens type determination unit 330 acquires information about the driving mechanism of the attached lens optical system 210 from a lens ROM (not shown) built in the lens barrel 200 and transmits this information to the lens driving amount setting unit 310. . The information on the drive mechanism includes information on whether the backlash amount of the drive mechanism is large or small and the backlash amount itself.

  FIG. 2 is a flowchart showing the AF operation of the camera according to the first embodiment. In the first embodiment, switching between the phase difference detection AF and the contrast detection AF is performed as follows. First, when the mirror up switch 75 is off, that is, when the quick return mirror 70 is down, the phase difference detection AF is performed. After the mirror up switch 75 is turned on and the up state of the quick return mirror 70 is detected, contrast detection AF is performed. As described above, the focusing lens 210c is normally adjusted by the phase difference detection method AF and then the mirror is raised, and further fine focus adjustment is performed by the contrast detection method AF.

  In step 100, it is determined whether or not a half-press switch (not shown) that is turned on when the shutter button (not shown) is half-pressed is turned on. In step 200, it is determined by the mirror up switch 75 whether or not the click return mirror 70 is in the mirror up state. When the mirror is being raised, the process proceeds to step 300 where the motor 240 drives the focusing lens 210c. Here, the lens is driven by contrast detection AF.

  In step 400, it is checked whether or not the focusing lens 210c has been driven by a predetermined amount, that is, the step amount. If the driving amount is insufficient, the process returns to step 300 to continue driving the focusing lens 210c. The step amount is set to a value larger than the backlash amount of the driving mechanism of the focusing lens 210c. When the focusing lens 210c is driven by a step amount, the process proceeds to step 500, and the driving of the focusing lens 210c by the motor 240 is stopped.

  In step 600, it is determined whether or not the focusing lens 210c is in the in-focus position. If it is in the in-focus position, the AF operation is terminated. If it is not at the in-focus position, the process proceeds to step 700 to calculate a focus evaluation value. In subsequent step 800, a calculation is performed to detect the position where the focus evaluation value is the maximum, that is, the in-focus position, from the focus evaluation value calculated this time and the focus evaluation value calculated so far. This in-focus position detection calculation will be described later. In step 900, it is determined whether or not a focus position has been found based on the focus position detection calculation result.

If the in-focus position is found, the process proceeds to step 1000, and the next lens driving amount is set by the following equation.
(Lens drive amount) = (Detected focus position) − (Current lens position) (1)
On the other hand, if the in-focus position is not found, the process proceeds to step 1100 to set the above-described step amount as the next lens drive amount.
(Lens drive amount) = (Step amount) (2)

  If it is determined in step 200 that the quick return mirror 70 is not in the mirror-up state, the process proceeds to step 1200, and it is determined whether or not the mirror-up switch 75 is turned off. When the mirror up switch 75 is off, the process proceeds to step 1300 and the detection operation by the phase difference detection AF detection element 100 is performed. For example, charge accumulation of a CCD built in the element is performed. In step 1400, the defocus amount is calculated based on the output of the phase difference detection AF detection element 100.

In step 1500, the lens driving amount is set by the following equation.
(Lens drive amount) = (position where the defocus amount is 0) − (current lens position) (3)
In step 1600, the lens is driven toward the in-focus position. Here, lens driving is performed by phase difference detection AF. In step 1700, it is confirmed whether or not the lens driving amount has reached the lens driving amount set by the above equation (3). If the driving amount is insufficient, the process returns to step 1600. When the focusing lens 210c is driven by the set lens driving amount, the process proceeds to step 1800, and the driving of the focusing lens 210c by the motor 240 is stopped.

If it is determined in step 1200 that the mirror up switch 75 is not turned off, the process proceeds to step 1900, and the quick return mirror 70 is mirrored up. In step 2000, based on the information regarding the driving mechanism of the focusing lens 210c input from the lens type determination unit 330, it is determined whether the backlash amount of the driving mechanism is large or small, and after mirror-up according to the backlash amount. The initial lens driving amount, that is, the above-described initial driving amount is set. This initial drive amount is the first lens drive amount when switching from the phase difference detection method AF to the contrast detection method AF. It is assumed that the backlash amount is small when the backlash amount is less than (focus depth of image plane) / 2, and that the backlash amount is large when the backlash amount is greater than (focus depth of focus equivalent to the image plane) / 2.
The backlash amount is small; (initial drive amount) = (step amount) (4),
Large amount of play; (Initial drive amount) = (Step amount) × 2- (Backlash amount) (5)

  The first lens drive amount after mirror up, that is, the initial drive amount, is set at a position separated by a step amount when the backlash is small from the lens position at the time of mirror up, that is, the focus position detected by phase difference detection AF. If the amount is large, this is a drive amount for shifting the focusing lens 210c to a position separated by ((step amount) × 2− (backlash amount)), and the position shifted by the initial drive amount is the start of contrast detection AF. Become position.

  3 and 4 are diagrams showing the movement of the lens by AF of the first embodiment, FIG. 3 shows the movement when the play amount of the lens driving mechanism is small, and FIG. 4 is the play amount of the lens drive mechanism. The movement when is large. 3 and 4, the vertical axis represents the focus evaluation value, and the horizontal axis represents the lens position from the closest end to the infinite end. When the focusing lens 210c is at the closest end, the closest subject is in focus, and when the focusing lens 210c is at the infinite end, the subject at infinity is in focus.

  Lens movement includes (a) movement by phase difference detection AF, (b) movement by initial drive to contrast detection AF start position, (c) movement by contrast detection AF, and (2) final alignment. There are four stages of movement by focal drive.

  (A) The movement by the phase difference detection method AF is the movement of the focusing lens 210c by the phase difference detection method AF in the mirror-down state. The “detection focus position” in the figure is the focus position detected by the phase difference detection method AF, and the value obtained by subtracting the current focusing lens position from the detection focus position is set as the lens driving amount. The focusing lens 210c is driven by the phase difference detection AF to set the detection focus position.

  (B) The movement by the initial drive to the contrast AF start position is determined by moving the focusing lens 210c from the detected focus position by the above-described initial drive amount when switching from the phase difference detection method AF to the contrast detection method AF as the mirror is raised. It is the movement when driving. As described above, the initial drive amount is determined by the above formula (4) or (5) according to the drive characteristics of the drive mechanism of the focusing lens 210c.

  (C) The movement by the contrast detection method AF is a movement when the focusing lens 210c is driven step by step to calculate a focus evaluation value, and this step driving is continued until a position where the focus evaluation value is maximized is found. (D) The final focus driving movement is determined by the current focusing from the position where the focus evaluation value is maximum, that is, the final focus position, when the position where the focus evaluation value is maximum is found by contrast detection AF. This is a movement when the focusing lens 210c is driven by a value obtained by subtracting the lens position.

  Before explaining the movement of the lens with reference to FIGS. 3 and 4, a method for detecting the position of the maximum focus evaluation value by the contrast detection method AF will be described with reference to FIG. In order to detect the final focus position with the maximum focus evaluation value, the focus evaluation value must be calculated while driving the lens step by step in the same direction in order to eliminate the influence of the play of the lens drive mechanism. Don't be. Also, if the step width is reduced, the final in-focus position with the maximum focus evaluation value can be accurately detected. However, if the step width is reduced, the number of times the focus evaluation value is calculated increases and the focusing speed is reduced. Become slow. In this embodiment, focus evaluation values are calculated at three locations P1, P2, and P3 that are lens-driven in the same direction, and the final in-focus position is detected accurately in a short time.

  As shown in FIG. 6, if the focus evaluation values are calculated at three locations P1, P2, and P3, the slope of the straight line passing through P1 and P2 is compared with the slope of the straight line passing through P2 and P3. A straight line L1 passing through P1 and P2 having a large value is selected. Next, a straight line L2 passing through P3 is selected from the straight lines having the same absolute value as that of the straight line L1 but having different signs. Then, the intersection of the straight lines L1 and L2 is set as the final focusing position. Here, the closer the central focus evaluation value calculation position P2 is to the detection focus position of the phase difference detection method AF, the detection error from the true focus position of the final focus position by the contrast detection method AF is minimized. It is confirmed by simulation and the like, and the final focus position can be determined by calculating the focus evaluation values at only three locations, and both the detection accuracy and the focus speed of the focus position can be improved. it can.

  First, as shown in FIG. 3, when the play amount of the lens drive mechanism is small, the initial drive amount = step amount is obtained by the above equation (4), and the lens is driven to the detection focus position by the phase difference detection method AF. The focusing lens 210c is initially driven by the step width from the detected in-focus position in the same direction as the above-described direction, and the position is shifted. Then, the lens driving direction is reversed from this position P1, and the focusing lens 210c is driven step by step to start the contrast detection AF.

  When the lens driving direction is reversed, the actual movement of the lens is reduced by the amount of play of the lens drive mechanism. However, when the amount of play of the lens drive mechanism is small, the amount of play can be ignored. The focus evaluation value is calculated, and then the focusing lens 210c is driven step by step to calculate the focus evaluation value at P2 and P3. In this case, the central position P2 is close to the detection focus position by the phase difference detection method AF, and therefore the position where the focus evaluation value is maximum by the focus evaluation values at the three positions P1 to P3, that is, the final focus position is accurately determined. And can be detected in a short time. Finally, the focusing lens 210c is driven by a value obtained by subtracting the current focusing lens position P3 from the final in-focus position. In FIG. 3, the detection focus position by the phase difference detection method AF and the final focus position by the contrast detection method AF are shown as the same position, but strictly speaking, there is an error in both.

  Next, as shown in FIG. 4, when the backlash amount of the lens drive mechanism is large, the initial drive amount = step amount × 2−backlash amount is obtained by the above equation (5) and detected by the phase difference detection method AF. The focusing lens 210c is initially driven by the initial drive amount from the detected focus position in the same direction as the lens drive direction to the focus position, and the position is shifted. Then, the lens driving direction is reversed from this position P0, and the focusing lens 210c is driven step by step to start the contrast detection AF.

  When the lens driving direction is reversed, the actual movement of the lens is reduced by the amount of play of the lens driving mechanism. That is, even if the lens driving command value for the step width is given to the focusing lens driving motor 240 at the position P0 and driven, the focusing lens 210c does not move by the amount of play of the lens driving mechanism, and the actual lens movement is ( Step width-play amount). The focusing lens 210c moves from the position P0 by (step width−backlash amount) to reach the position P1. In the lens driving after the position P1, since the play is already narrowed, the focusing lens 210c moves by the step width.

  The first focus evaluation value is calculated at the position P1, and then the focusing lens 210c is driven step by step, and the focus evaluation value is calculated at P2 and P3. In this case, the central position P2 is close to the detection focus position by the phase difference detection method AF, and therefore the position where the focus evaluation value is maximum by the focus evaluation values at the three positions P1 to P3, that is, the final focus position is accurately determined. And can be detected in a short time. Finally, the focusing lens 210c is driven by a value obtained by subtracting the current focusing lens position P3 from the final in-focus position. In FIG. 4, the detection focus position by the phase difference detection method AF and the final focus position by the contrast detection method AF are shown as the same position, but strictly speaking, there is an error in both.

  3 and 4, the lens is driven by the initial driving amount in the same direction as the lens driving direction from the detection focus position by the phase difference detection method AF to the detection focus position by the phase difference detection method AF, and the contrast detection method AF. An example is shown in which the focusing lens 210c is set to the starting position. The lens is driven by the initial drive amount in the direction opposite to the lens driving direction from the detection focus position by the phase difference detection method AF to the detection focus position by the phase difference detection method AF, in other words, the lens position is returned by the initial drive amount. An example in which the focusing lens 210c is set to the start position of the contrast detection method AF will be described.

FIG. 5 shows the movement of the lens when the initial driving is performed in the direction opposite to the driving direction of the phase difference detection method AF and the backlash of the lens driving mechanism is large. When initial driving is performed in the direction opposite to the driving direction of the phase difference detection method AF and the backlash amount of the lens driving mechanism is large, the initial driving amount is obtained by the following equation.
(Initial drive amount) = (Step amount) × 2 (6)
Then, the focusing lens 210c is initially driven by the initial drive amount from the detection focus position in a direction opposite to the direction in which the lens is driven to the detection focus position by the phase difference detection method AF, and the position is shifted. Then, the contrast detection method AF is started by reversing the lens driving direction again from this position P0.

  When the lens driving direction is reversed in the initial driving, the actual movement of the lens is reduced by the amount of play of the lens driving mechanism. That is, even when the lens driving command value (step width × 2) is given to the focusing lens driving motor 240 at the detection focus position and driven, the focusing lens 210c does not move by the amount of play of the lens driving mechanism. The movement of the lens is (step width × 2-backlash). Accordingly, the focusing lens 210c moves from the detection focus position by (step width × 2−backlash amount) and reaches the position P0.

  The lens driving direction is reversed again from this position P0, and the focusing lens 210c is driven step by step to start the contrast detection method AF. Since the lens driving direction is reversed again, the focusing lens 210c does not move by the amount of play of the lens driving mechanism even if the lens driving command value for the step width is given to the focusing lens driving motor 240 to drive the actual lens. The movement of (step width-backlash amount) reaches position P1. In the lens driving after the position P1, since the play is already narrowed, the focusing lens 210c moves by the step width.

  After calculating the first focus evaluation value at the position P1, the focusing lens 210c is driven step by step, and the focus evaluation value is calculated at P2 and P3. In this case, the central position P2 is close to the detection focus position by the phase difference detection method AF, and therefore the position where the focus evaluation value is maximum by the focus evaluation values at the three positions P1 to P3, that is, the final focus position is accurately determined. And can be detected in a short time. Finally, the focusing lens 210c is driven by a value obtained by subtracting the current focusing lens position P3 from the final in-focus position. In FIG. 5, the detection focus position by the phase difference detection method AF and the final focus position by the contrast detection method AF are shown as the same position, but strictly speaking, there is an error in both.

<< Second Embodiment of the Invention >>
FIG. 7 is a graph showing a focus position detection error with respect to a deviation amount from the true focus position of the central focus evaluation value calculation position P2. When the central focus evaluation value calculation position P2 is at the true focus position, the position where the focus evaluation value calculated based on the focus evaluation values at the three places P1 to P3 by the method described with reference to FIG. Correctly matches the true in-focus position, and the detection error is zero. On the other hand, even when the central focus evaluation value calculation position P2 is shifted ± (step width) / 2 back and forth from the true focus position, if the position having the maximum focus evaluation value is obtained by the method described with reference to FIG. The detection error is zero.

  Further, since the “detection focus position” by the phase difference detection method AF described above is considered to be close to the true focus position, the central focus evaluation value calculation position P2 is ±± from the detection focus position of the phase difference detection method AF. If the position is shifted by (step width) / 2 and the position of the maximum focus evaluation value is calculated based on the focus evaluation values at the three locations P1 to P3, the time is short as in the first embodiment described above. Can accurately adjust the focus. The configuration of the second embodiment is the same as the configuration shown in FIG. 1, and the AF operation of the camera is the same as the AF operation shown in FIG. Explained.

FIG. 8 shows the movement of the lens when the backlash of the lens driving mechanism is small. The initial drive amount when the backlash amount is smaller than (focal depth in terms of image plane) / 2 or smaller is a value obtained by adding (step width) / 2 to the initial drive amount of (4) above, and is obtained by the following equation. .
The amount of play is small; (initial drive amount) = (step width) × (1 + 1/2) (7)
Compared to the case where the backlash amount of the first embodiment shown in FIG. 3 is small, the second embodiment is the same as the first embodiment except that the initial drive amount is increased by (step width) / 2. As shown in FIG. 8, the central focus evaluation value calculation position P2 is set to a position that is (step width) / 2 before the detection focus position of the phase difference detection method AF.

The initial driving amount when the backlash amount is larger than (focal depth in terms of image plane) / 2 is a value obtained by adding (step width) / 2 to the initial driving amount of (5) above, and is obtained by the following equation.
The amount of play is small; (initial driving amount) = (step width) × (2 + 1/2) (8)
Compared to the case where the backlash amount of the first embodiment shown in FIG. 4 is large, the second embodiment is the same as the first embodiment except that the initial drive amount is increased by (step width) / 2. Although illustration of lens movement in this case is omitted, the central focus evaluation value calculation position P2 is set to a position that is (step width) / 2 before the detection focus position of the phase difference detection method AF.

  Similarly, in the case where the initial driving is performed in the direction opposite to the driving direction of the phase difference detection AF, the initial driving amount may be increased by (step width) / 2.

<< Third Embodiment of the Invention >>
There are many types of interchangeable lenses, and even a lens with a small amount of play may increase the amount of play due to aging or temperature change. Furthermore, the amount of play varies depending on conditions such as the posture of the camera. Therefore, the initial drive amount of the first and second embodiments described above may not be sufficient for lenses that cannot grasp the amount of play or for lenses that are expected to increase in amount of play. Therefore, an embodiment in which the initial drive amount is increased for such a lens will be described. The configuration of the third embodiment is the same as the configuration shown in FIG. 1, and the AF operation of the camera is the same as the AF operation shown in FIG. Explained.

  FIG. 9 shows the movement of the lens when the initial drive amount is (step width × 3). In this case, if the first step drive immediately after the start of the contrast detection AF is driven to the position P0 and then the second step drive is driven to the position P1, the backlash amount can be sufficiently reduced by two step drives. If the focus evaluation value is calculated as described above at the subsequent positions P1 to P3, the accurate position of the maximum focus evaluation value can be obtained.

  Note that the initial drive amount is not limited to (step width × 3), and may be, for example, 5 times when there is play, and 3 times when there is no play. Further, as described above, since the central focus evaluation value calculation position P2 may be shifted by ± (step width) / 2 from the detection focus position of the phase difference detection method AF, the initial drive amount is set to (step width) / It may be increased or decreased by 2.

  As described above, according to the embodiment, accurate focus adjustment can be executed in a short time. The AF other than the contrast detection method is not limited to the phase difference detection method, and may be, for example, an external light passive AF or an external light active AF.

The figure which shows the structure of 1st Embodiment. The figure which shows AF operation | movement of 1st Embodiment The figure which shows the motion of the lens by AF of 1st Embodiment The figure which shows the motion of the lens by AF of 1st Embodiment The figure which shows the motion of the lens by AF of 1st Embodiment The figure explaining the detection method of the position where a focus evaluation value becomes the maximum A graph showing the focus position detection error with respect to the amount of deviation from the true focus position of the center focus evaluation value calculation position The figure which shows the motion of the lens by AF of 2nd Embodiment The figure which shows the motion of the lens by AF of 3rd Embodiment

Explanation of symbols

20 Image sensor 100 Phase difference detection AF detection element 210c Focusing lens 240 Focusing lens drive motor 300 Defocus amount calculation unit 310 Lens drive amount setting unit 320 Focus evaluation value calculation unit 330 Lens type determination unit

Claims (5)

Lens driving means for driving the focusing lens;
A first focus adjusting means for searching for a focus position while driving the lens by the lens driving means and adjusting the focus of the lens;
Second focus adjusting means for adjusting the focus by driving the lens by the lens driving means in a focus adjustment method different from the first focus adjusting means;
Control means for performing focus adjustment by the first focus adjustment after driving the lens by an initial drive amount by the lens driving means from the position of the lens when the focus adjustment by the second focus adjustment means is completed. When,
An initial drive amount determining unit that determines the initial drive amount in accordance with a drive characteristic of the lens driving unit. The focus adjustment apparatus according to claim 1,
The focus adjustment apparatus, wherein the initial drive amount determination unit determines the initial drive amount according to a type of the lens drive unit. The focus adjustment apparatus according to claim 1,
The focus adjustment apparatus, wherein the initial drive amount determination means determines the initial drive amount according to a backlash amount of the lens drive means. In the focus adjustment apparatus according to any one of claims 1 to 3,
The focus adjusting apparatus, wherein the first focus adjusting means is a contrast detecting focus adjusting means, and the second focus adjusting means is a phase difference detecting focus adjusting means.   A camera comprising the focus adjustment device according to claim 1.

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