JP5868109B2 - Optical apparatus, lens barrel, and automatic focusing method - Google Patents

Description

  The present invention relates to automatic focus adjustment (AF) of optical instruments.

  In Patent Documents 1 and 2, the first and second focus lenses, the first drive means for driving the first focus lens, the second drive means for driving the second focus lens, Control means for controlling the second drive means is disclosed. Patent Document 3 discloses a camera in which a wobbling lens for hill-climbing AF is provided separately from the focus lens, and the wobbling lens is held at the midpoint during manual focusing. Patent Document 4 discloses a configuration for performing phase difference AF and contrast AF in a so-called mirrorless camera that does not have a finder and a mirror that guides a light beam thereto. Note that providing a phase difference AF function on the imaging surface of the imaging element is disclosed in Patent Document 5.

JP 2011-123339 A JP 2006-227414 A JP 09-197259 A JP 2011-139353 A JP 2011-135191 A

  There has not been proposed in the past how AF is performed when two focus lens groups are driven by two driving means using two types of focus detection methods (for example, phase difference AF and contrast AF). . The movement accuracy and speed of the focus lens during AF are determined by the characteristics of the actuator that drives the focus lens. In general, accuracy and speed are contradictory characteristics. For example, when a stepping motor with a feed screw is used to drive the focus lens, the pitch of the feed screw is reduced if accuracy is increased, and is increased if speed is increased. There is a need to. The focus lens of a single lens reflex interchangeable lens requires a large amount of movement from infinity to the nearest and high-speed, high-accuracy focus drive. However, if you try to increase the speed, you can increase accuracy at the expense of accuracy. I was forced to sacrifice speed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical apparatus capable of performing AF at high speed and with high accuracy when two focus lens groups are provided by two drive means using two types of focus detection methods. And

The optical apparatus according to the present invention includes a first focus lens group driven by the first driving unit and a second focus driven by the second driving unit at a higher resolution and lower speed than the first driving unit. A first mode in which at least one of the lens groups is moved so that the phase difference between the two subject images is small; and the first focus lens group and the first focus lens group so that the evaluation value representing the sharpness of the subject image reaches a peak. And a control unit capable of executing a second mode for moving at least one of the second focus lens groups, and the control unit includes a second drive unit that is required in the first mode. When the driving amount is larger than the first threshold, the first focus lens group is driven by the first driving unit, and the driving amount of the second driving unit is equal to or less than the first threshold. If the drives the second focus lens unit by the second driving means, said in a second mode, a time limit for completing the driving and the driving amount of the second driving means required driving time When the driving speed of the second driving means calculated from the above is larger than the second threshold, the first focus lens group is driven by the first driving means, and the driving speed of the second driving means is calculated. Is less than or equal to the second threshold value, the second focus lens group is driven by the second driving means.

  According to the present invention, an object of the present invention is to provide an optical apparatus capable of performing AF at high speed and high accuracy when two focus lens groups are provided by two drive means using two types of focus detection methods. And

It is a block diagram of the camera system of this embodiment. 3 is a flowchart for explaining the operation of the camera system shown in FIG. 1.

  FIG. 1 is a block diagram of the camera system of the present embodiment. The camera system includes an interchangeable lens (lens barrel) 10 and a camera main body 30 configured to be attachable (detachable). The optical apparatus of the present invention includes a camera body (imaging device) that can exchange lenses, a camera system that includes a camera body that can exchange lenses and an interchangeable lens, a lens-integrated camera, and a lens barrel. The camera body 30 includes a digital still camera, a digital video camera, and the like.

  This embodiment is a mirrorless lens interchangeable camera in which a mirror box made up of a main mirror and a sub mirror that guides light from an object provided in a conventional single-lens reflex camera to a finder and a focus detection unit is removed. The present invention can also be applied to an optical apparatus having a box.

  The interchangeable lens 10 houses a photographing optical system that forms an optical image of an object. The photographing optical system includes a first lens group 11 as a first focus lens group, a second lens group 12 as a variator lens group as a variable power system, a third lens group 13 as a second focus lens group, and a light amount. A diaphragm 14 for adjusting

  Reference numeral 15 denotes a first group barrel that holds the first lens group 11, and has a rack portion 15 a that engages with the lead screw 18 a of the first stepping motor 18, and is linearly guided by a straight bar (not shown). . As a result, when the stepping motor 18 is driven, the first lens group 11 moves straight in the optical axis direction and performs focusing.

  Reference numeral 16 denotes a second lens barrel that holds the second lens group 12 and is driven straight in the optical axis direction by an external operation member (not shown) during zooming.

  Reference numeral 17 denotes a third lens barrel that holds the third lens group 13. The third lens barrel 17 has a rack portion 17 a that engages with the lead screw 19 a of the stepping motor 19 and is linearly guided by a straight bar (not shown). As a result, by driving the stepping motor 19, the third lens group 13 is driven straight in the optical axis direction to perform wobbling and focusing.

  The first stepping motor 18 is a first driving means that drives the first group barrel 15 and has a lead screw 18a that is an output shaft. The first stepping motor 18 is a motor that can be driven at a high speed with respect to the second stepping motor 19. The lead of the lead screw 18a is larger than the lead of the lead screw 19a and has a larger driving range. As a result, the driving amount of one pulse by the first stepping motor 18 is large and the resolution (first resolution) (and hence the positioning accuracy) is low, but the first lens group 11 is moved from infinity to the nearest (first). At a speed).

  The second stepping motor 19 is a second driving means that drives the third group barrel 13 and has a lead screw 19a that is an output shaft. The lead of the lead screw 19a is smaller than the lead of the lead screw 18a and the driving range is small. Thereby, the driving amount of one pulse by the second stepping motor 19 is small, and the third lens group 13 is moved at a second resolution higher than the first resolution (that is, with high positioning accuracy) than the first speed. It can be driven at a small second speed.

  As described above, in the present embodiment, the high-speed or high-precision drive constitutes the actuator by making the characteristics of the two stepping motors and the lead screw lead different.

  In addition, the kind of actuator is not limited, You may use other actuators, such as an ultrasonic motor and a voice coil. For example, the first lens group 11 may be driven at high speed using an ultrasonic motor and a cam.

  20, 21, and 22 are absolute value encoders for detecting the driving amounts of the first lens group 11, the second lens group 12, and the third lens group 13, and are fixed to the zone brush fixed to each lens barrel. A zone substrate having a zone pattern disposed in the portion. When the lens barrel is driven, the zone brush moves with respect to the zone substrate to switch the zone pattern to be contacted, and the absolute position of each lens group is detected.

  Reference numeral 23 denotes a lens CPU, which is a lens control means (microcomputer) that communicates with the camera CPU 32 to transmit and receive information and control each part of the interchangeable lens 10. Specifically, focus adjustment (AF) information and exposure control information are input from the camera CPU 32 and drive control of the stepping motors 18 and 19 and the diaphragm 14 is performed.

  The camera body 30 includes an image sensor 31 and a camera CPU 32.

  The image sensor 31 is a CMOS or CCD that photoelectrically converts an optical image of a subject (object) formed by the photographing optical system. The imaging light flux from the subject passes through the imaging optical system of the interchangeable lens 10 and forms an image on the surface of the image sensor 31.

  As disclosed in Patent Document 5, the image sensor 31 has a plurality of sets of pixels that receive light passing through only a partial region of the exit pupil of the photographing optical system. An output corresponding to the phase difference (defocus amount) between the two subject images is generated from a plurality of sets of pixels (focus detection pixels).

  The image sensor 31 detects the phase difference (corresponding to the defocus amount) between the two subject images on the imaging surface via the focus detection element. As a camera system, it is possible to realize phase difference AF in which at least one of the first and second focus lens groups is moved so that the phase difference is small. Further, the first and second focus are set so that the evaluation value representing the sharpness obtained from the signal processed by the signal processing circuit (not shown) by A / D converting the signal based on the output of the imaging pixel becomes a peak. Contrast AF that moves at least one of the lens groups can be realized.

  The camera CPU 32 communicates with the lens CPU 23 to transmit / receive information, and based on the output of the image sensor 31, the camera body control means for controlling the entire camera, such as recording of video signals, automatic focus adjustment (AF), and exposure. (Microcomputer).

  Specifically, AF distance measurement range, AF method, and photometry range are selected based on the condition of the subject (whether it is a moving object, etc.) and the size on the imaging surface, and distance measurement for contrast AF and phase difference AF is performed. Based on the result, an AF drive command is output to the lens CPU 23.

  The camera CPU 32 can execute a plurality of AF modes. In this embodiment, the camera CPU 32 executes a phase difference AF mode (first mode) and a contrast AF mode (second mode). The AF mode can be manually set by a user operating an operation unit (not shown), but may be stored as a program in a memory (not shown) connected to the camera CPU 32.

  In contrast AF, the focus lens is moved in the optical axis direction to be positioned at the in-focus position corresponding to the maximum value (peak value) of the sharpness evaluation value (contrast value). A method of positioning after returning from the peak position after passing the peak position is called hill-climbing AF.

  If a stepping motor with a feed screw is used to drive the focus lens, the position of the focus lens can be driven accurately, and when the sharpness signal during movement changes from rising to decreasing, the sharpness signal is at the maximum value. It can be returned to the focus lens position.

  When the sharpness in the in-focus state changes, it is determined that the subject distance has changed, and restarting is performed, and the focus lens is stopped again at the position where the sharpness reaches the maximum value, and the in-focus state is obtained.

  In order to detect whether the focus lens is in the infinite side or the near side from the current position of the focus lens, a predetermined pulse minute drive (wobbling) is performed on the focus lens on the near side and the infinite side. Mountain climbing AF is started in the direction where the sharpness signal is large.

  The phase difference AF is the imaging surface phase difference AF in this embodiment, but an AF sensor may be used, and the AF sensor does not pass through the imaging optical system even in internal measurement using a light beam that has passed through the imaging optical system. External measurement using luminous flux may be used.

  FIG. 2 is a flowchart for explaining the operation of the camera system (automatic focus adjustment method), and “S” stands for a step. The operation shown in FIG. 2 can be embodied as a program executed by a computer, is executed by the camera CPU 32 or the lens CPU 23, and is stored in a memory (not shown) of the lens barrel 10 or the camera body 30.

  First, the camera CPU 32 starts AF when it is confirmed that a first stroke switch SW1 signal of a release switch (not shown) is generated (S1001).

  The camera CPU 32 determines whether the AF method is phase difference AF (S1002). If the user has set the AF method with an operation unit (not shown), the camera CPU 32 follows that. Alternatively, since the phase difference AF is generally faster than the contrast AF, the phase difference AF may be performed first. However, even in this case, if the AF signal cannot be obtained from the focus detection pixel, the contrast AF may be selected. Furthermore, when the phase difference AF is first selected in step S1002 and is not focused, it may be switched to the contrast AF next time (and thereafter).

  If the AF method is phase difference AF (YES in S1002), the camera CPU 32 determines the defocus amount and the in-focus direction, and drives the second stepping motor 19 (drive pulse amount) or the corresponding defocus amount. The focus amount is transmitted to the lens CPU 23 (S1003).

  Next, based on the information sent from the camera CPU 32, the lens CPU 23 determines whether the driving amount of the second stepping motor 19 necessary for eliminating the phase difference is less than a predetermined driving amount (below the first threshold). It is determined whether or not (S1005). If the driving amount of the second stepping motor 19 is equal to or less than the predetermined driving amount, the current position is close to the in-focus position, and if it is larger than the predetermined driving amount, the current position is far from the in-focus position.

  If the driving amount of the second stepping motor 19 is equal to or less than the predetermined driving amount (YES in S1005), the lens CPU 23 drives the third lens group 13 with high accuracy by the second stepping motor 19 (S1006). On the other hand, if the driving amount of the second stepping motor 19 is larger than the predetermined driving amount (NO in S1005), the first lens group 11 is moved at a high speed by the first stepping motor 18 and the phase difference between the first lens group 11 is reached. Is driven by a driving amount necessary to eliminate the problem (S1007). The driving speed of the second stepping motor 19 in S1006 is smaller than the driving speed of the first stepping motor 18 in S1007.

  In this embodiment, the determination in S1005 is performed by the lens CPU 23, but may be performed by the camera CPU 32. In this case, the characteristics of the two actuators are transmitted in advance from the lens CPU 23 to the camera CPU 32, and information on the selected actuator is transmitted from the camera CPU 32 to the lens CPU 23 together with the driving amount in S1003.

  After S1006 or S1007, the camera CPU 32 performs in-focus determination (S1012). If it is in focus (YES in S1012) (if there is no other input such as SW2), it waits in that state. At this time, it may be switched to contrast AF in S1002 as described above.

  On the other hand, if the AF method is contrast AF (NO in S1002), the camera CPU 32 determines whether or not the evaluation value (contrast value) is less than or equal to a predetermined evaluation value (third threshold or less) (S1004). If the evaluation value is less than or equal to the predetermined evaluation value, the current position is far from the in-focus position so that the evaluation value cannot be obtained. It will be in.

  If the evaluation value is equal to or less than the predetermined evaluation value (YES in S1004), the camera CPU 32 determines to detect a location where the evaluation value is larger than the predetermined evaluation value in a predetermined direction (S1008). On the other hand, if the evaluation value is larger than the predetermined evaluation value (NO in S1004), the camera CPU 32 determines to perform wobbling and mountain climbing AF (S1009).

  After S1008 or S1009, the camera CPU 32 transmits the drive (pulse) amount (or defocus amount) and drive time of the second stepping motor 19 to the lens CPU 23 (S1010). The drive time is a time limit until the drive is completed, and is intended to prevent the image acquisition time in which the drive of the focus lens is repeated periodically. By including the driving time information, the lens CPU 23 can know that the driving command is based on the contrast AF.

  Next, the lens CPU 23 determines whether or not the driving speed of the second stepping motor 19 calculated based on the driving amount and driving time of the second stepping motor 19 is equal to or lower than a predetermined driving speed (less than a second threshold value). Judgment is made (S1011). When the driving speed is equal to or lower than the predetermined driving speed (YES in S1011), the lens CPU 23 proceeds to S1006, and when the driving speed is higher than the predetermined driving speed (NO in S1011), the lens CPU 23 proceeds to S1007. To do. As a result, the high-speed first stepping motor 18 can be used when a high driving speed is required, and the second stepping motor can be used when the driving speed can be provided by the second stepping motor 19.

  If the current position is far from the in-focus position, the driving amount increases and the driving speed generally increases. Therefore, the process proceeds from S1011 to S1007, and the driving amount decreases because the driving amount decreases when the current position is close to the in-focus position. And the process proceeds from S1011 to S1006.

  In the present embodiment, when the first and second focus lenses are driven by two driving means using a plurality of AF methods, AF can be performed at high speed and with high accuracy.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary. The present invention also includes a lens barrel having a lens CPU 23 that controls the first and second stepping motors 18 and 19 in accordance with a drive command transmitted from the camera body 30. All the steps shown in FIG. 2 may be performed based on information obtained from the camera CPU 32 by the lens CPU 23.

  The optical apparatus can be applied to camera applications.

DESCRIPTION OF SYMBOLS 10 ... Lens barrel (optical apparatus), 11 ... 1st lens group (1st focus lens group), 13 ... 3rd lens group (2nd focus lens group), 18 ... 1st stepping motor (1st , 19... Second stepping motor (second driving means), 23... Lens CPU (control means), 30... Camera body (optical device), 31. )

Claims (11)

At least one of the first focus lens group driven by the first drive means and the second focus lens group driven by the second drive means at a higher resolution and lower speed than the first drive means is 2 The first focus lens group and the second focus lens group so that the evaluation value representing the sharpness of the subject image has a peak, and the first mode in which the phase difference between the two subject images is reduced. A control unit capable of executing a second mode in which at least one of them is moved;
The control means includes
In the first mode, when the required driving amount of the second driving unit is larger than the first threshold, the first focus lens group is driven by the first driving unit, When the driving amount of the second driving means is less than or equal to the first threshold, the second driving lens group is driven by the second driving means,
In the second mode, the driving speed of said second driving means is calculated from a time limit for completing the driving and the driving amount of the second driving means required driving time than the second threshold value When it is larger, the first focus lens group is driven by the first driving means, and when the driving speed of the second driving means is equal to or lower than the second threshold, the second driving means drives the second focus lens group. An optical apparatus that drives a focus lens group. 2. The optical apparatus according to claim 1, wherein the driving time of the second driving unit does not take a periodical image acquisition time. The optical apparatus, said first focus lens group, the second focus lens group, according to claim 1 or 2, further comprising a first drive means and said second driving means Optical equipment. The control means in the second mode,
When the evaluation value is larger than a third threshold value, the second focus lens group is wobbled to detect a focus direction in which the evaluation value reaches a peak, and the focus direction detected in the wobbling Drive to
If the evaluation value is less than the third threshold value, to claim 1 wherein the evaluation value by driving the first focus lens unit and detects the larger position than the third threshold value 4. The optical apparatus according to any one of items 3 . The control means optical apparatus according to any one of claims 1 to 4, characterized in that the process proceeds to the second mode when not in focus the first mode. An image sensor that photoelectrically converts an optical image of a subject;
The image pickup device receives a plurality of light beams that pass through only a partial region of an exit pupil of a photographing optical system that has the first focus lens group and the second focus lens group to form an optical image of a subject. It has a set of pixels, the optical device according to any one of claims 1 to 4, characterized in that to produce an output corresponding to the phase difference. Wherein, in said first mode, from said plurality of sets of pixels according to claim 6, characterized in that the transition to the second mode when the output corresponding to the phase difference can not be obtained Optical equipment. At least one of the first focus lens group driven by the first drive means and the second focus lens group driven by the second drive means at a higher resolution and lower speed than the first drive means is 2 The first focus lens group and the second focus lens group so that the evaluation value representing the sharpness of the subject image has a peak, and the first mode in which the phase difference between the two subject images is reduced. Used in an optical instrument having control means capable of executing a second mode in which at least one of them is moved;
In the first mode, when the driving amount of the second driving unit is larger than a first threshold value, the first driving unit drives the first focus lens group by the first driving unit, and the second driving unit. Driving the second focus lens group by the second driving means when the driving amount is less than or equal to the first threshold;
In the second mode, when the driving speed of said second driving means is calculated from the time limit for the drive amount and drive completion is the driving time of the second drive means is greater than a second threshold Drives the first focus lens group by the first driving means, and when the driving speed of the second driving means is equal to or lower than the second threshold value, the second focus lens group is driven by the second driving means. Step of driving,
An automatic focusing method characterized by comprising: The optical apparatus includes a camera body and a lens that can be attached to the camera body,
In the first mode, the necessary driving amount of the second driving means or information corresponding thereto is output, and in the second mode, the necessary driving amount of the second driving means is output. And camera body control means for outputting driving time or information corresponding thereto,
Lens control means for receiving the output and controlling driving of the first focus lens group by the first driving means and driving of the second focus lens group by the second driving means; the optical device according to any one of claims 1 to 7, characterized in that it has. The optical apparatus includes a camera body and a lens that can be attached to the camera body,
In the first mode, information and driving amount of driving means selected from the first driving means and the second driving means and information corresponding to the driving means are output, and in the second mode, Camera body control means for outputting information on the driving means selected from the first driving means and the second driving means, the driving amount and the driving time or information corresponding thereto, and receiving the output, according to any one of claims 1 to 7, characterized in that it has a, a lens control means for controlling the driving of said first focusing lens or the second focus lens group unit by the selected drive means Optical equipment. A first focus lens group driven by the first drive means and a second focus lens group driven by the second drive means at a higher resolution and lower speed than the first drive means; A lens barrel detachable from the camera body,
When the driving amount of the second driving means necessary for reducing the phase difference between the two subject images sent from the camera body is larger than a first threshold, the first driving means The first focus lens group is driven, and when it is equal to or less than the first threshold, the second focus lens group is driven by the second driving means,
The amount of driving of the second driving means and the time limit for completing the driving required to drive the second driving means sent from the camera body to peak the evaluation value representing the sharpness of the subject image When the drive speed of the second drive means calculated from the drive time is greater than a second threshold, the first focus lens group is driven by the first drive means, and the first A lens barrel characterized by driving the second focus lens group by the second driving means when the threshold value is less than 2.