JP2008145627A - Optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption and the brightness variation of a screen when moving a light shielding member other than diaphragm blades to perform pupil time-division AF. <P>SOLUTION: An optical device includes: diaphragm blades 62 and 63 which form a diaphragm aperture allowing a luminous flux to pass therethrough and are moved to change the size of the diaphragm aperture; a light shielding member 31a wherein a fixed aperture 31b allowing the luminous flux to pass therethrough is formed; and actuators 46, 47, 34, and 35 which move the light shielding member to a light shielding position for screening a part of the diaphragm aperture and a non light shielding position for not screening the diaphragm aperture. A control means controls the actuators so that an extent of movement between the non light shielding position and the light shielding position of the light shielding member is varied in accordance with the size of the diaphragm aperture. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical apparatus such as an image pickup apparatus that forms a plurality of images used for focus detection and the like in time series by moving a light shielding member provided separately from a diaphragm blade that forms a diaphragm aperture.

  In Patent Document 1, the light beam passing area is moved in time series by moving a light shielding member different from the diaphragm blade at or near the pupil position of the imaging optical system, and formed by the light flux from each area. A technique for performing focus detection of an imaging optical system based on a phase difference between a plurality of subject images is disclosed. Such a focus detection method is also called a pupil time division method, and autofocus (AF) by this method is called a pupil time division method AF.

In the optical apparatus of Patent Document 1, in the vicinity of the diaphragm blades, two light shielding plates each having a fixed opening are alternately inserted into and removed from the optical path, thereby moving the light flux passage region in time series.
JP-A-8-94923 (paragraphs 0021 to 0029, FIG. 1, etc.)

  However, in the optical apparatus disclosed in Patent Document 1, the light shielding plate is always moved to a position where light can be shielded even when the aperture diameter of the aperture is small, regardless of the aperture diameter of the aperture. This is disadvantageous in terms of power consumption for driving the light shielding plate.

  With respect to this problem, it is possible to always open the aperture when performing the time-series pupil division AF, and to reduce the amount of movement of the light shielding plate. However, in this case, particularly in moving image capturing, there arises a problem that the brightness of the screen changes discontinuously.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical apparatus capable of suppressing power consumption and screen brightness fluctuation when performing a pupil time-division AF by moving a light shielding member different from a diaphragm blade. One.

  An optical apparatus according to an aspect of the present invention includes a diaphragm aperture that forms a diaphragm aperture through which a light beam passes, and a light shield that has a diaphragm blade that moves to change the size of the diaphragm aperture and a fixed aperture through which the light beam passes. A member, and an actuator that moves the light shielding member to a light shielding position that covers a part of the aperture opening and a non-light shielding position that does not cover the aperture opening. And it has the control means which controls an actuator so that the amount of movements between the non-light-shielding position and the light-shielding position of the light shielding member differs according to the size of the aperture opening.

  Note that an optical device that performs focus detection by moving the light shielding member and photoelectrically converting a plurality of images formed in time series also constitutes another aspect of the present invention.

  In the present invention, when the size of the aperture opening is large, the amount of movement of the light shielding member is made smaller than when the aperture is small. For this reason, it is possible to reduce the power consumption as compared with the case where the light shielding member is always largely moved so as to correspond to the small aperture opening. In addition, when performing focus detection (AF), the size of the aperture opening can be changed in accordance with the subject brightness, so that variations in screen brightness due to movement of the light shielding member can be suppressed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the structure of a pupil division unit and a light amount adjustment unit in a lens barrel of a video camera (optical apparatus) that is an embodiment of the present invention. In FIG. 1, an upper side of an optical axis O of an imaging optical system, which will be described later, is a vertical sectional view, and a lower side of the optical axis O is a horizontal sectional view. FIG. 2 is a cross-sectional view showing the overall structure of the lens barrel. FIG. 3 is an exploded perspective view of the lens barrel. 4 to 6 are front views of the time-series pupil division unit as viewed from the front side (subject side or object side). FIG. 4 shows a non-light-shielded state, FIG. 5 shows a lower light-shielded state, and FIG. Indicates the upper shading state.

  In these drawings, reference numeral 1 denotes a first lens unit arranged on the most object side. Reference numeral 2 denotes a second lens unit that moves in the optical axis direction and performs zooming. Reference numeral 3 denotes a fixed third lens unit. Reference numeral 4 denotes a fourth lens unit that moves in the direction of the optical axis and corrects and focuses the image plane variation during zooming.

  Reference numeral 5 denotes a rear frame fixed to a video camera body (not shown). Reference numeral 6 denotes a first lens barrel that holds the first lens unit 1. Reference numeral 7 denotes a front frame for fixing the first lens barrel 6 with screws 8, 9 and 10. A shift base 11 is sandwiched and held between the front frame 7 and the rear frame 5.

  Reference numeral 12 denotes a first coupling sheet metal. The first coupling sheet metal 12 has a slope portion 12a engaged with the projection 7a of the front frame 7 and an end surface portion 12b engaged with the projection 5a of the rear frame 5, thereby shifting the front frame 7 to the shift base. 11 and the rear frame 5 so as to be drawn in the optical axis direction. Reference numeral 13 denotes a screw for attaching the coupling sheet metal 12 to the rear frame 5.

  Reference numeral 14 denotes a second coupling sheet metal. The second coupling sheet metal 14 is engaged with a projection (not shown) of the front frame 7 and a projection (not shown) of the rear frame 5 in the same manner as the first coupling sheet metal 12, and the front frame 7 is shifted to the shift base. 11 and the rear frame 5 so as to be drawn in the optical axis direction. Reference numeral 15 denotes a screw for attaching the second coupling sheet metal 14 to the rear frame 5.

  Reference numerals 16 and 17 denote guide bars, both ends of which are held by the rear frame 5 and the first lens barrel 6 and fixed so as to extend in parallel to the optical axis.

  Reference numeral 18 denotes a second lens barrel that holds the second lens unit 2. The sleeve portion 18a of the second lens barrel 18 is engaged with the guide bar 16 so as to be movable in the optical axis direction. Further, the U groove portion 18 b of the second lens barrel 18 engages with the guide bar 17. As a result, the second lens barrel 18 is held movably in the optical axis direction while being prevented from rotating around the guide bar 16.

  Reference numeral 19 denotes a zoom motor, which includes a drive unit 19a formed of a stepping motor, a feed screw unit 19b that is an output shaft of the drive unit 19a, and a holding metal plate 19c that holds the drive unit 19a and the feed screw unit 19b. ing. Reference numerals 20 and 21 denote screws for fixing the holding metal plate 19 c of the zoom motor 19 to the front frame 7. A rack 22 is attached to the second lens barrel 18 and is biased in the optical axis direction with respect to the second lens barrel 18 by a rack spring 23. The rack 22 is rotatable around an axis parallel to the optical axis.

  The rack tooth portion 22 a of the rack 22 meshes with the feed screw portion 19 b of the zoom motor 19. The rack 22 converts the rotation of the zoom motor 19 (feed screw portion 19b) into a driving force in the optical axis direction and transmits it to the second lens barrel 18.

  Reference numeral 24 denotes a photo interrupter, which switches between a state in which a light shielding portion (not shown) formed in the second lens barrel 18 is in the slit portion 24a between the light projecting element and the light receiving element and a state in which it is not. Is detected. Based on the detection signal from the photo interrupter 24, it can be detected that the second lens barrel 18 is located at the reference position. The position of the second lens barrel 18 is detected by monitoring the output from the photo interrupter 24 and resetting the second lens barrel 18 to the reference position, and then inputting the second lens barrel 18 to a zoom motor 19 constituted by a stepping motor. This can be done by counting the number of drive pulses.

  Reference numeral 25 denotes a substrate on which the photo interrupter 24 is attached. Reference numeral 26 denotes a screw for fixing the substrate 25 to the front frame 7.

  Next, the configuration of the pupil time division unit 30 for performing focus detection (AF) will be described. The pupil time division unit 30 is arranged at or near the pupil position of the imaging optical system. The pupil time division unit 30 includes a shift base 11, a shift frame 31, and a light blocking member 31 a that blocks a part of light from the subject. In the center of the light shielding member 31a, a fixed opening 31b having an inner diameter equal to or larger than an open opening diameter of a light amount adjusting unit described later is formed.

  Reference numeral 32 denotes a roll prevention bar that is prevented from rotating around the optical axis with respect to the shift base 11 and is movably mounted in a horizontal direction within a plane orthogonal to the optical axis (hereinafter referred to as an optical axis orthogonal plane). is there. The roll prevention bar 32 is attached to the shift frame 31 so as to be prevented from rotating around the optical axis and movable in the vertical direction within the plane orthogonal to the optical axis. Thereby, the shift frame 31 can be shifted with respect to the shift base 11 in the horizontal and vertical directions without rotating in the plane orthogonal to the optical axis. Then, so-called pupil time division is performed by shifting the shift frame 31.

  33 is a magnet base. Magnets 34 and 35 for driving the shift frame 31 in the horizontal and vertical directions and detecting the position are fixed to the magnet base 33 by press fitting. By fixing the magnets 34 and 35 to the magnet base 33, the relative positional relationship between the magnet base 33 and the magnets 34 and 35 is maintained constant. The magnet base 33 is fixed to the shift frame 31 with screws 36. Therefore, the positions of the magnets 34 and 35 are fixed with respect to the shift frame 31, and the magnets 34 and 35 can be used for detecting the position of the shift frame 31 as will be described later.

  The shift frame 31 and the magnet base 33 are coupled by screws 36 with a metal plate 37 sandwiched between them. As the material of the metal plate 37, for example, stainless steel is suitable.

  Reference numerals 38, 39, and 40 denote balls disposed between the shift base 11 and the magnet base 33, and are disposed at three positions around the optical axis. By arranging the metal plate 37 between the balls 38, 39, 40 and the magnet base 33, the ball is pressed against the magnet base 33, which is a molded component, when the camera is impacted. Formation of a dent can be prevented. That is, it is possible to prevent the drive characteristics of the magnet base 33 from deteriorating.

  On the other hand, between the balls 38, 39, 40 and the shift base 11, ball holders 41, 42, 43 formed in a U shape with stainless steel or the like are arranged. The ball holders 41, 42, and 43 are press-fitted into a hole (not shown) formed in the shift base 11, and hold the balls 38, 39, and 40 in a rotatable manner.

  The material of the balls 38, 39, 40 is preferably stainless steel so that it is not attracted to the magnets 34, 35 disposed in the vicinity thereof.

  Next, the actuator that drives the magnet base 33 and the shift frame 31 will be described. As shown in FIG. 1, the magnets 34 and 35 are magnets magnetized in opposite directions on the inner diameter side and the outer diameter side. 44 and 45 are front yokes for closing the magnetic flux in the optical axis direction front side of the magnets 34 and 35. The front yokes 44 and 45 are attracted and fixed to the magnets 34 and 35.

  Reference numerals 46 and 47 denote coils fixed to the shift base 11 by adhesion. Reference numerals 48 and 49 denote rear yokes for closing the magnetic flux on the rear side in the optical axis direction of the magnets 34 and 35. The rear yokes 48 and 49 are disposed on the opposite side of the magnets 34 and 35 with the coils 46 and 47 interposed therebetween, and are held by the shift base 11. These magnets 34 and 35, front yokes 44 and 45, rear yokes 48 and 49, and coils 46 and 47 form a magnetic circuit.

  The force for securely bringing the balls 38, 39, 40 into contact with the shift base 11 (the end surfaces in the optical axis direction of the ball holders 41, 42, 43) and the magnet base 33 (metal plate 37) is the magnets 34, 35. And the rear yokes 48 and 49. When the magnet base 33 is biased in the direction approaching the shift base 11 by this attractive force, the three balls 38, 39, 40 are aligned with the optical axis end surfaces of the three ball holders 41, 42, 43 and the metal plate 37. In the pressed state.

  Each surface with which the three balls 38, 39, 40 abut is spread in a direction perpendicular to the optical axis. The nominal diameters of the three balls 38, 39, and 40 are the same. For this reason, the shift frame 31 can be moved within the optical axis orthogonal plane without causing a tilt with respect to the optical axis.

  As described above, in the pupil time division unit 30, the magnet base 33 is urged against the shift base 11 by using the attractive force between the magnets 34 and 35 and the rear yokes 48 and 49. For this reason, parts, such as a spring member for biasing, become unnecessary, and the pupil time division unit 30 can be downsized.

  When a current is passed through the coils 46 and 47, a Lorentz force is generated by the interaction of the magnetic lines generated in the magnets 34 and 35 and the coils 46 and 47 in a direction orthogonal to the magnetization boundary of the magnets 34 and 35. Thereby, the magnet base 33 moves in a direction orthogonal to the optical axis (optical axis orthogonal direction).

  In a state in which a current for center positioning is passed through the coils 46 and 47, as shown in FIG. 4, the magnet base 33 has the center O1 of the fixed opening 31b of the shift frame 31 (the light shielding member 31a) as the light of the imaging optical system. It is positioned with respect to the shift base 11 so as to be positioned on the axis O. In this state, the light shielding member 31 a does not cover the aperture opening formed by the light amount adjustment unit 61.

  When a current is passed through the coil 46 in a specific direction, the magnet base 33 moves upward as shown in FIG. When a current is passed through the coil 46 in a direction opposite to the specific direction, the magnet base 33 moves downward as shown in FIG. When a current is passed through the coil 47 in a specific direction and in the opposite direction, the magnet base 33 moves in the left direction and the right direction, respectively. In these shift states, the light shielding member 31 a covers a part of the aperture opening (the upper or lower region) formed by the light amount adjustment unit 61.

  Thus, the pupil time division unit 30 of the present embodiment has a so-called moving magnet type actuator.

  In this way, the magnet base 33 and the shift frame 31 can be driven in two directions orthogonal to the optical axis that are orthogonal to each other. The magnet base 33 and the shift frame 31 can be freely moved within a specific range in the plane orthogonal to the optical axis by combining these vertical and horizontal driving.

  The friction when the magnet base 33 moves in the direction perpendicular to the optical axis is between the balls 38, 39, 40 and the metal plate 37 and between the balls 38, 39, 40 and the ball holders 41, 42, 43. It is only rolling friction that occurs in each. For this reason, the magnet base 33 (that is, the shift frame 31) can move very smoothly in the plane orthogonal to the optical axis, and a small amount of movement can be controlled, even though the attraction force is applied. . The frictional force can be further reduced by applying lubricating oil to the balls 38, 39, and 40.

  Next, a configuration for detecting the positions of the magnet base 33 and the shift frame 31 will be described. 1 to 3, reference numerals 51 and 52 denote hall elements that convert magnetic flux density into electric signals, which are soldered to a flexible printed cable (hereinafter referred to as FPC) 53. The FPC 53 is positioned and fixed to the shift base 11. Further, by fixing the FPC pressing metal fitting 54 to the shift base 11 with screws, the FPC 53 is prevented from floating and the positions of the Hall elements 51 and 52 are prevented from being shifted. With the above configuration, a position sensor that detects the positions of the magnet base 33 and the shift frame 31 is formed.

  When the magnet base 33 and the shift frame 31 are driven in the vertical direction and the horizontal direction, changes in the magnetic flux density are detected by the Hall elements 51 and 52, respectively, and an electrical signal indicating the change in the magnetic flux density is transmitted from the Hall elements 51 and 52. Is output. Based on the electrical signals from the hall elements 51 and 52, the positions of the magnet base 33 and the shift frame 31 can be detected. The magnets 34 and 35 are driving magnets and are also used as position detection magnets.

  Next, a method for determining the center position (optical axis alignment) of the shift frame 31 will be described. As shown in the upper side of the optical axis O in FIG. 1, the optical axis alignment is based on the wall portions 11 b provided on the upper and lower inner circumferences of the opening formed in the shift base 11. As a design value, the distance from the optical axis O of the imaging optical system to the wall portion 11b is set to be the same. Further, as shown below the optical axis O in FIG. 1, two wall portions 11 b are also provided on the inner peripheral left and right sides of the opening in the shift base 11. That is, wall portions 11b are provided at four locations on the top, bottom, left, and right of the opening formed in the shift base 11.

  First, the movable unit including the shift frame 31 and the magnet base 33 is moved in the vertical direction and the horizontal direction, which are orthogonal to the optical axis, and abutted against the wall portion 11b, and the outputs of the Hall elements 51 and 52 at the respective abutting positions. Read.

  The position of the shift frame 31 (hereinafter referred to as the center position) corresponding to the read center value of the Hall elements 51 and 52 is the center of the shift frame 31 (the center of the fixed opening 31b) is the optical axis of the imaging optical system. The position coincides with O. This center value information is stored in a memory (not shown) mounted on the camera body. As described above, when the positioning control of the shift frame 31 is performed at the center position, energization of the coils 46 and 47 is controlled so that the outputs of the Hall elements 51 and 52 coincide with the center value stored in the memory.

  Thus, the shift base 11 is a member having the wall portion 11b for positioning the center of the movable unit, and is also used as a member for holding the coils 46, 47 and the rear yokes 48, 49. This contributes to a reduction in the number of parts.

  A light amount adjusting unit 61 changes the amount of light incident on the imaging optical system, and moves the two diaphragm blades 62 and 63 in the direction orthogonal to the optical axis by the diaphragm motor 61a to change the aperture diameter of the diaphragm. The light quantity adjustment unit 61 is fixed to the shift base 11 with screws 64.

  Reference numeral 65 denotes a third lens barrel that holds the third lens unit 3. Reference numeral 66 denotes a third lens frame that holds the third lens barrel 65 and is fixed to the shift base 11 with screws 67 and 68.

  Reference numerals 71 and 72 denote guide bars which are held at both ends by the rear frame 5 and the shift base 11 and extend in parallel to the optical axis direction. Reference numeral 73 denotes a fourth lens barrel that holds the fourth lens unit 4. The sleeve portion 73a of the fourth lens barrel 73 is engaged with the guide bar 71 so as to be movable in the optical axis direction. Further, the U-groove (not shown) of the fourth lens barrel 73 is engaged with the guide bar 72, so that the rotation of the fourth lens barrel 73 around the optical axis is prevented. Thereby, the fourth lens barrel 73 is held so as to be movable in the optical axis direction.

  Reference numeral 74 denotes a coil, which is fixed to the fourth lens barrel 73 and constitutes a focus motor (voice coil motor) that drives the fourth lens barrel 73 in the optical axis direction. Reference numeral 75 denotes a drive magnet constituting the focus motor. 76 and 77 are yoke members for closing the magnetic flux in the focus motor. When a current is passed through the coil 74, a Lorentz force is generated by the interaction of magnetic lines of force generated between the magnet 75 and the coil 74, and the fourth lens unit 73 and the fourth lens unit 4 are driven in the optical axis direction. .

  The fourth lens barrel 73 holds a sensor magnet (not shown) that is multipolarly magnetized in the optical axis direction. An MR sensor (focus encoder) 78 that reads a change in magnetic force accompanying the movement of the sensor magnet is fixed by a screw at a position facing the sensor magnet in the rear frame 5. By using the signal from the MR sensor 78, the amount of movement of the fourth lens barrel 73, that is, the fourth lens unit 4 from the reference position can be detected.

  Reference numeral 81 denotes an optical filter in which an infrared cut filter and a low-pass filter are bonded. An image sensor (CMOS sensor) 82 is capable of high-speed reading.

  FIG. 7 shows an electrical configuration of the video camera of this embodiment. In this figure, the components of the lens barrel described in FIGS. 1 to 6 are assigned the same reference numerals as in FIGS.

  Reference numeral 107 denotes an aperture encoder as position detecting means, which has a Hall element disposed in an aperture motor 61a that drives the light quantity adjusting unit 61, and uses this Hall element to determine the rotational positional relationship between the rotor and the stator, that is, the aperture. The positions of the blades 62 and 63 are detected.

  Reference numeral 108 denotes a control circuit composed of a CPU or the like that controls the entire video camera. The control circuit 108 performs energization control on the coils 46 and 47 in order to shift the shift frame 31 of the pupil time division unit 30 in the vertical direction or the horizontal direction.

  A camera signal processing circuit 110 performs signal processing such as amplification processing and gamma correction processing on the output from the image sensor 82. The video signal generated through these processes is displayed on a display (not shown) or recorded on a recording medium (not shown) (semiconductor memory, optical disk, hard disk, magnetic tape, etc.).

  Also, the luminance signal among the video signals is input to an AE (automatic exposure) gate 111 and an AF (autofocus) gate 112. The AE gate 111 and the AF gate 112 set an optimum signal extraction range for exposure determination and focusing in the entire screen. The size of the signal extraction range by these gates 111 and 112 may be variable, or a plurality of gates may be provided.

  Reference numeral 113 denotes an AF signal processing circuit, which generates a signal used for AF according to the number of AF gates 112. Specifically, the AF signal processing circuit 113 shifts an image (luminance signal) acquired in each state where the center position of the fixed opening 31b of the shift frame 31 (the light shielding member 31a) in the pupil time division unit 30 is shifted. That is, the phase difference is calculated. Information on the calculated phase difference is output to the control circuit 108.

  Note that there is a TV-AF (contrast AF) method as an AF method for general moving image shooting. In this embodiment, a case where pupil time division AF is performed in moving image capturing will be described, but TV-AF and pupil time division AF may be used in combination. For example, it is also possible to use the TV-AF in order to quickly focus on the in-focus range using pupil time-division AF, and then focus on a more accurate in-focus position. Further, when the video camera can capture still images, pupil time division AF may be used.

  Reference numeral 114 denotes a zoom switch. Reference numeral 115 denotes a zoom tracking memory. The zoom tracking memory 115 stores position information of the fourth lens unit 4 corresponding to the subject distance and the position of the second lens unit 2 at the time of zooming. Note that the memory in the control circuit 108 may be used as the zoom tracking memory 115.

  For example, when the zoom switch 114 is operated, the control circuit 108 maintains a specific positional relationship between the second and fourth lens units 2 and 4 calculated based on information in the zoom tracking memory 115. The zoom motor 19 and the focus motor are controlled. As a result, image plane fluctuations associated with zooming are corrected, and zooming in a focused state can be performed.

  Further, the control circuit 108 calculates an average value of the luminance signal output that has passed through the AE gate 111 as a reference value in order to obtain appropriate exposure. Then, the aperture motor 61a is controlled to control the aperture diameter, that is, the amount of light so that the output of the aperture encoder 107 matches the reference value.

  Next, the pupil time division AF in the present embodiment will be described in more detail.

  One frame image in normal video imaging is output every 1/60 second. In the present embodiment, the CMOS sensor used as the image sensor 82 can perform high-speed reading, and can capture, for example, six images, for example, multiple times in 1/60 second.

  In the present embodiment, during pupil time-division AF, one of the six images (an image captured during 1 / 6th of a 1/60 second: hereinafter referred to as an AF image) is transferred to the shift frame 31. Capture in a state shifted from the center position in the first direction. The first direction here may be any one of up, down, left and right. Further, another one of the AF images is captured in a state where the shift frame 31 is shifted in the second direction opposite to the first direction. The remaining four images are captured with the shift frame 31 placed at the center position, and two or more of these are combined to produce a one-frame image output.

  Note that the capture range of the AF image captured in a state where the shift frame 31 is shifted from the center position may be the entire image or a part thereof.

  As described above, in order to support a CMOS sensor that can capture an image at high speed, the shift frame 31 needs to be able to shift from the center position in a short time of 1/6 of 1/60 second.

  In a state where the shift frame 31 is shifted from the center position, the center of the light beam from the subject at (or near) the pupil position of the imaging optical system is shifted from the optical axis of the imaging optical system. For this reason, when the focus of the imaging optical system with respect to the subject is shifted, a shift (phase difference) occurs between the two images captured while being shifted in the first and second directions. The amount and direction of this phase difference are calculated by the AF signal processing circuit 113. Then, the control circuit 108 obtains the in-focus position of the fourth lens unit 4 based on the calculated phase difference, and controls the focus motor so that the fourth lens unit 4 moves to that position. Thereby, pupil time division AF is completed.

  FIG. 8 is a flowchart mainly showing the operation of the control circuit 108 in this embodiment. This operation is executed according to a computer program stored in the control circuit 108.

  Here, a case where pupil time division AF is performed by shifting the shift frame 31 of the pupil time division unit 30 in the horizontal direction will be described. Note that the pupil time division AF may be performed by shifting the shift frame 31 in the vertical direction, and the operation in this case is the same except that the shift direction is different.

  In step S301, the control circuit 108 reads the aperture diameter of the light amount adjustment unit 61, that is, the positions of the aperture blades 62 and 63, where the acquired image is adjusted to the appropriate amount of light from the output of the aperture encoder 107 (see FIG. To detect).

  In step S <b> 302, the control circuit 108 calculates a shift amount from the center position of the shift frame 31 corresponding to the aperture opening diameter of the light amount adjustment unit 61.

  9A to 9C show the relationship between the aperture diameter of the aperture and the shift amount of the shift frame 31 as viewed from the optical axis direction. FIG. 9A shows a state where the aperture opening diameter of the light quantity adjustment unit 61 is an open diameter and the shift frame 31 is at the center position. At this time, the center O1 of the fixed opening 31b of the light shielding member 31a coincides with the optical axis (center of the aperture opening) O of the imaging optical system including the light amount adjustment unit 61, and the shift frame 31 is stopped by the light shielding member 31a. Do not block. That is, the light shielding member 31a is in the non-light shielding position.

  FIG. 9B shows a state where the aperture diameter of the light amount adjustment unit 61 is a small aperture diameter, and the shift frame 31 is shifted leftward from the center position by the shift amount SA1. At this time, the light shielding member 31a is in a first light shielding position where a part thereof blocks the right end region of the aperture opening.

  9B indicates the center of the fixed opening 31b in a state where the shift frame 31 is shifted rightward from the center position by the shift amount SA1. At this time, the light shielding member 31a is in a second light shielding position that blocks the left end region of the aperture opening by another part of the peripheral portion.

  Further, FIG. 9C shows a state in which the aperture diameter of the light amount adjustment unit 61 is an open diameter, and the shift frame 31 is shifted leftward from the center position by the shift amount SA2. At this time, the light shielding member 31a is at a first light shielding position that partially shields a slightly larger area on the right end side of the aperture opening. The shift amount SA2 is smaller than the shift amount SA1.

  Note that O2 in FIG. 9C indicates the center of the fixed opening 31b in a state where the shift frame 31 is shifted rightward from the center position by the shift amount SA2. At this time, the light shielding member 31a is at a second light shielding position where a part of the periphery of the fixed opening 31b blocks a slightly large area on the left end side of the aperture opening.

  As described above, the control circuit 108 moves the movement amount SA1 between the non-light-shielding position and the light-shielding position (the first light-shielding position and the second light-shielding position) of the light shielding member 31a according to the size of the aperture opening. The actuator of the pupil time division unit 30 is controlled so that SA2 is different. More specifically, the actuator is controlled so that the shift amount of the light shielding member 31a increases as the size of the aperture opening decreases, and conversely, the shift amount of the light shielding member 31a decreases as the size of the aperture opening increases.

  In step S303, the control circuit 108 uses the signal from the hall element 52 to control the actuator of the pupil time division unit 30 (energization to the coil 47), and shifts the shift frame 31 by the shift amount calculated in step S302. Shift left. Then, in this shifted state, an AF image is captured by the image sensor 82 in step S304.

  Next, in step S305, the control circuit 108 controls energization to the coil 47 using a signal from the hall element 52, and shifts the shift frame 31 to the right by the shift amount calculated in step S302. Then, in this shifted state, another AF image is captured by the image sensor 82 in step S306.

  Next, in step S307, the control circuit 108 controls energization to the coil 47 using the signal from the hall element 52 and the center value corresponding to the center position of the shift frame 31 stored in the memory. The shift frame 31 is returned to the center position.

  Next, in step S308, the control circuit 108 causes the AF signal processing circuit 113 to calculate phase difference information of the AF image captured in steps S304 and S306. Further, the control circuit 108 obtains the in-focus position of the fourth lens unit 4 based on the calculated phase difference.

  Next, in step S309, the control circuit 108 determines whether or not the difference between the calculated focus position of the fourth lens unit 4 and the current position of the fourth lens unit 4 is within the focus range. . If it is out of focus range, in step S310, the focus motor is controlled to move the fourth lens unit 4 to the calculated focus position. Then, the process proceeds again to step S309.

  On the other hand, if it is within the focusing range, this flow is terminated.

  As described above, according to the present embodiment, when pupil time-division AF is performed, the shift amount of the light shielding member 31a is changed in accordance with the aperture diameter. Thereby, since the shift amount of the light shielding member 31a when the aperture opening is large can be suppressed, the power consumption can be reduced compared to the case where the light shielding member is largely shifted regardless of the size of the aperture opening.

  Further, since pupil time-division AF can be performed without changing the size of the aperture opening set according to the brightness of the subject, it is possible to reduce the brightness fluctuation of the image during AF.

  In the above embodiment, the case where the shift amount of the light shielding member 31a is changed using the result of detecting the positions of the diaphragm blades 62 and 63 (the size of the aperture opening) of the light quantity adjustment unit has been described. However, the shift amount of the light shielding member may be changed according to the luminance information from the image sensor 82. In this case, the size of the aperture opening of the light quantity adjustment unit is not directly detected, but the size of the next aperture opening is set based on the luminance information before driving the light quantity adjustment unit. This corresponds to changing the shift amount of the light shielding member 31a in accordance with the size of the light shielding member.

  In the above embodiment, the video camera has been described. However, the present invention can also be applied to other optical devices such as a digital still camera and an interchangeable lens.

Sectional drawing of the pupil time division unit and light quantity adjustment unit which were mounted in the video camera which is an Example of this invention. Sectional drawing of the lens-barrel part of the video camera of an Example. The disassembled perspective view of the lens-barrel part of an Example. The front view of the pupil time division unit (non-light-shielding state) of an Example. The front view of the pupil time division unit (1st light-shielding state) of an Example. The front view of the pupil time division unit (2nd light-shielding state) of an Example. The block diagram which shows the electric constitution of the video camera of an Example. The flowchart which shows operation | movement of the video camera of an Example. In Example 1, it is a schematic diagram which shows the relationship with an aperture stop when the light shielding member of the pupil time division unit exists in a non-light-shielding position. In Example 1, it is a schematic diagram which shows the relationship between an aperture diameter (small) and the shift amount of the light shielding member. In Example 1, it is a schematic diagram which shows the relationship between an aperture diameter (large) and the shift amount of the light shielding member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st lens unit 2 2nd lens unit 3 3rd lens unit 4 4th lens unit 5 Rear part frame 6 1st lens barrel 7 Front part frame 11 Shift base 18 2nd lens barrel 19 Zoom motor 31 Shift frame 31a Light shielding Member 33 Magnet base 34, 35 Magnet 37 Metal plate 38, 39, 40: Ball 46, 47 Coil 51, 52 Hall element 61 Light quantity adjustment unit 62, 63 Aperture blade 82 Imaging element 108 Control circuit 113 AF signal processing circuit

Claims (4)

A diaphragm blade that forms a diaphragm aperture through which a light beam passes and moves so as to change the size of the diaphragm aperture;
A light shielding member having a fixed opening through which the light beam passes;
An actuator for moving the light shielding member to a light shielding position covering a part of the aperture opening and a non-light shielding position not covering the aperture opening;
An optical apparatus comprising: control means for controlling the actuator so that the amount of movement of the light shielding member between the non-light shielding position and the light shielding position differs according to the size of the aperture opening. . The actuator moves the light shielding member to a first light shielding position covering a part of the aperture opening and a second light shielding position covering another part of the aperture opening,
The said control means controls the said actuator so that the movement amount between the said non-light-shielding position of each said light-shielding member and each said light-shielding position may differ according to the magnitude | size of the said aperture opening. The optical apparatus according to 1. A position detecting means for detecting the position of the diaphragm blade;
The optical apparatus according to claim 1, wherein the control unit controls the actuator so as to change a moving amount of the light shielding member in accordance with an output of the position detection unit. The optical apparatus according to any one of claims 1 to 3, wherein focus detection is performed using an output from an image pickup element obtained in a state where the positions of the light shielding members are different.