JP2007187712A - Imaging apparatus and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for an imaging apparatus, to which an interchangeable lens can be attached to/detached from, for accurately measuring backlash amount related to the driving system of a focusing lens. <P>SOLUTION: A DC motor for driving the focus lens in the interchangeable lens is mounted inside the imaging apparatus which the interchangeable lens can be attached to/detached from. In a state in which the interchangeable lens is attached to the imaging apparatus, the DC motor is rotated in the CW direction and is stopped by a pulse train Pa first. Next, the DC motor is driven reversely in the CCW direction by a pulse train Pb. The rotational amount of the DC motor in a time zone Tb, when the load current of the DC motor becomes substantially 0 after starting the reverse driving, is measured as the amount of backlash. Thus, the backlash amount related to the driving system of the focus lens is accurately measured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique of an imaging apparatus in which an interchangeable lens can be attached and detached.

  In a camera (imaging device) in which an interchangeable lens is detachable, the amount of backlash in the focus lens drive system often changes depending on the lens.

  On the other hand, the backlash in the focus lens driving system causes a problem that the lens position is not known when the moving direction of the focus lens is reversed during autofocus (AF).

  As a technique for grasping such backlash, for example, there is one disclosed in Patent Document 1. According to this technique, the backlash amount is obtained by approximate calculation using the focal length information of the photographing lens.

JP 2001-100089 A

  However, in the technique of Patent Document 1, since the backlash amount is obtained by approximate calculation or the like, it is difficult to accurately grasp the backlash amount.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique of an image pickup apparatus in which an interchangeable lens can be attached and detached that can accurately measure a backlash amount in a focus lens drive system.

  In order to solve the above-mentioned problem, the invention of claim 1 is an imaging device in which an interchangeable lens having a lens position changing mechanism for changing the position of a focus lens by power input via a coupler is detachable. (a) an electric actuator that generates the power and can be output to the interchangeable lens side via the coupler; (b) load measuring means that measures a load related to the electric actuator; and (c) an output of the electric actuator. A displacement amount measuring means for measuring the displacement amount according to the above, and (d) the displacement amount during the light load driving in which the electric actuator is driven with a light load even when the interchangeable lens is mounted is measured by the displacement amount measuring means. A backlash amount relating to a focus lens drive system including the coupler and the lens position changing mechanism based on a displacement amount during the light load drive. It is obtained.

  According to a second aspect of the invention, in the imaging apparatus according to the first aspect of the invention, the light load is substantially no load.

  According to a third aspect of the invention, in the imaging apparatus according to the first or second aspect of the invention, the load measuring means includes (b-1) a means for measuring a load current of the electric actuator as the load. .

  According to a fourth aspect of the present invention, in the image pickup apparatus according to any one of the first to third aspects, the measurement control means includes (d-1) a first driving mechanism for driving the electric actuator in a predetermined displacement direction. (D-2) second driving means for stopping driving of the electric actuator after driving by the first driving means and re-driving the electric actuator in a direction opposite to the predetermined displacement direction; -3) a means for measuring, by the displacement amount measuring means, a displacement amount during a period of driving with the light load from the start of re-driving by the second driving means as the displacement amount during the light load driving.

  The invention according to claim 5 is the imaging apparatus according to any one of claims 1 to 4, wherein the measurement control means is (d-4) when the interchangeable lens is attached. Means for measuring the amount of displacement during load driving are provided.

  The invention according to claim 6 is the imaging apparatus according to any one of claims 1 to 5, wherein the measurement control means is (d-5) during the light load driving when the imaging apparatus is activated. Means for measuring the amount of displacement of the displacement by the displacement amount measuring means.

  The invention according to claim 7 is the imaging apparatus according to any one of claims 1 to 6, wherein the measurement control means is (d-6) when the zoom change related to the interchangeable lens is changed. Means for measuring a displacement amount during driving by the displacement amount measuring means.

  The invention according to claim 8 is the imaging apparatus according to any one of claims 1 to 7, wherein the measurement control means is (d-7) at the time of automatic focusing using the focus lens. A means for measuring a displacement amount during light load driving by the displacement amount measuring means;

  According to a ninth aspect of the present invention, in the imaging apparatus according to any one of the first to eighth aspects of the present invention, (e) an image sensor capable of acquiring an image relating to a subject, and (f) acquired by the image sensor. And an automatic focusing unit that performs automatic focusing based on the contrast of the image, and the automatic focusing unit performs position control of the focus lens based on the backlash amount.

  The invention according to claim 10 is an imaging system comprising an interchangeable lens and an imaging device to which the interchangeable lens can be attached and detached, wherein the interchangeable lens is focused by power input via a coupler (a-1). The image pickup apparatus includes a lens position changing mechanism that changes the position of the lens, and (b-1) an electric actuator that generates the power and can output to the interchangeable lens side through the coupler, and (b- 2) load measuring means for measuring a load related to the electric actuator; (b-3) displacement amount measuring means for measuring a displacement amount related to the output of the electric actuator; and (b-4) the electric actuator is the interchangeable lens. Measurement control means for measuring a displacement amount during light load driving that is driven with a light load even in a mounted state by the displacement amount measurement means, and based on the displacement amount during light load driving, the coupler and the A backlash amount relating to the focus lens driving system including the lens position changing mechanism is acquired.

  According to the first to tenth aspects of the present invention, even when an interchangeable lens equipped with a lens position changing mechanism that changes the position of the focus lens by the power input from the electric actuator in the imaging apparatus via the coupler is light. The amount of displacement during light load driving in which the electric actuator is driven by the load is measured, and the backlash amount related to the focus lens driving system including the coupler and the lens position changing mechanism is acquired. As a result, the backlash amount in the focus lens drive system can be measured with high accuracy.

  In particular, in the invention of claim 2, since the light load is substantially no load, the backlash amount can be easily measured.

  In the invention of claim 3, since the load current of the electric actuator is measured as a load, the load related to the electric actuator can be easily measured.

  In the invention of claim 4, when the electric actuator is driven in a predetermined displacement direction, the drive is stopped, and when the electric actuator is redriven in the direction opposite to the predetermined displacement direction, The amount of displacement during the drive period is measured as the amount of displacement during light load driving. As a result, the backlash amount can be measured with higher accuracy.

  In the invention of claim 5, since the displacement amount during light load driving is measured when the interchangeable lens is mounted, the backlash amount can be measured at an appropriate timing.

  In the invention of claim 6, since the amount of displacement during light load driving is measured when the image pickup apparatus is activated, the amount of backlash can be measured at an appropriate timing.

  In the seventh aspect of the invention, since the displacement amount during light load driving is measured when the zoom of the interchangeable lens is changed, the backlash amount can be measured at an appropriate timing.

  In the invention of claim 8, since the displacement amount during light load driving is measured at the time of automatic focusing using the focus lens, the backlash amount can be measured at an appropriate timing.

  In the ninth aspect of the invention, since the automatic focusing means that performs automatic focusing based on the contrast of the image acquired by the image sensor performs position control of the focus lens based on the backlash amount, the position control of the focus lens is performed. It can be done smoothly.

<Overview of imaging system>
1 and 2 are diagrams showing an external configuration of an imaging system 100 according to the embodiment of the present invention. Here, FIG. 1 is a front external view of the imaging system 100, and FIG. 2 is a rear external view of the imaging system 100. FIG. 3 is a conceptual diagram showing a cross section viewed from the position III-III in FIG.

  As shown in FIG. 1, an imaging system 100 includes a single-lens reflex digital still camera that includes a camera body (camera body) 101 and an interchangeable lens 102 that is detachably mounted at the front center of the camera body 101. It is configured as.

  In FIG. 1, a camera body (imaging device) 101 includes a mount portion Mt on which the interchangeable lens 102 is mounted at the front center, an attach / detach button 149 for attaching / detaching the interchangeable lens near the mount portion Mt, and a front left end portion. A grip unit 113 for the photographer to hold and an AF auxiliary light emitting unit 163 for emitting auxiliary light for AF are provided.

  Further, the camera body 101 has a control value setting dial 146 for setting a control value at the upper right portion of the front surface, a mode setting dial 142 for switching the photographing mode at the upper left portion of the front surface, and an exposure on the upper surface of the grip portion 113. A release button 147 for instructing the start is provided, and for example, a pop-up flash 162 that emits light for irradiating the subject at the time of flash photography is incorporated.

  The mount portion Mt is provided with a coupler MC for performing mechanical connection with the mounted interchangeable lens 102. Power (driving force) generated by a focus lens driving DC motor (hereinafter abbreviated as “motor”) 114 can be output (transmitted) to the interchangeable lens 102 via the coupler MC. In the interchangeable lens 102, the lens position changing mechanism 104 changes the position of the focus lens 103 in the front-rear direction LX of the interchangeable lens 102 using power input from the motor 114 via the coupler MC and the rotating rod 105. Is possible.

  In FIG. 1, a battery storage chamber and a card storage chamber are provided inside the grip portion 113. For example, four AA batteries are housed in the battery compartment as a power source for the camera, and a memory card 176 for recording image data of the photographed image is detachably housed in the card compartment. It is like that.

  The mode setting dial 142 is used for various camera modes (still image shooting mode for shooting still images, movie shooting mode for shooting movies, playback mode for playing back captured images, and communication for data communication with external devices. Mode, etc.).

  The release button 147 is a two-stage switch configured to be able to perform an operation in the “half-pressed state S1” that is pressed halfway and an operation in the “full-pressed state S2” that is further pressed. When the release button 147 is half-pressed in the still image shooting mode, a preparation operation (preparation operation for setting an exposure control value, focus adjustment, etc.) for acquiring a still image of the subject is executed, and the release button 147 is all set. When pressed, a photographing operation (a series of operations for exposing the image sensor and performing predetermined image processing on an image signal obtained by the exposure) is executed.

  In FIG. 2, a finder window 108 is provided in the upper center of the back surface of the camera body 101. A subject image from the interchangeable lens 102 is guided to the finder window 108. The photographer can view the subject by looking through the viewfinder window 108. More specifically, the subject image that has passed through the interchangeable lens 102 is reflected upward by the mirror mechanism 122 (see FIG. 6), thereby forming the subject image on the focusing screen and the image passing through the pentaprism. The subject image can be visually recognized by looking through the eyepiece. The finder window 108 incorporates a liquid crystal display unit for displaying various information indicating the shutter speed, aperture value, and other states of the imaging system 100. Therefore, the photographer can check various states of the imaging system 100 by looking through the finder window 108.

  A rear monitor 107 is provided at substantially the center of the rear surface of the camera body 101. The rear monitor 107 is configured, for example, as a color liquid crystal display, and displays a menu screen for setting shooting conditions and the like, and plays back and displays the shot image recorded on the memory card 176 in the playback mode. is there.

  A main switch 141 is provided at the upper left of the rear monitor 107. The main switch 141 is a two-point slide switch. When the contact is set to the left “OFF” position, the power is turned off. When the contact is set to the right “ON” position, the power is turned on.

  A direction selection key 144 is provided on the right side of the rear monitor 107. This direction selection key 144 has a circular operation button, and it is possible to detect the upper, lower, left and right four-direction pressing operations and the upper right, upper left, lower right, and lower left pressing directions in the operation buttons. It has become. Note that the direction selection key 144 is configured to detect a pressing operation of a push button in the center, in addition to the pressing operations in the eight directions.

  A setting button group 143 including a plurality of buttons for setting a menu screen, deleting an image, and the like is provided at the left position of the rear monitor 107.

  As shown in FIG. 3, a rotary encoder (hereinafter abbreviated as “encoder”) 115 for detecting the rotation amount (rotation angle) of the motor 114 is attached to the motor 114, and the output change of the encoder 115 is changed. Is detected by the pulse counter 116. That is, the amount of rotational displacement related to the output of the motor 114 is measured using the encoder 115 and the pulse counter 116. On the other hand, the current value flowing through the motor 114 can be detected by a current value measuring unit 118 that measures a load (load current) related to the motor 114.

  The control unit 121 is a main microcomputer that comprehensively controls the imaging system 100 based on an instruction from the photographer input to the release button 147 and the like. In the imaging system 100, rotation control of the motor 114 that functions as an electric actuator can be performed via the motor driver 117 based on the drive signal from the control unit 121.

<Backlash in the drive system of the focus lens 103>
In the drive system of the focus lens 103 including the lens position changing mechanism 104 and the coupler MC, there is a backlash due to the engagement of the gear train in the lens position changing mechanism 104 or the fitting backlash in the coupler MC. When the moving direction of 103 is reversed, a situation occurs in which the focus lens 103 does not move despite the motor 114 being operated. Since such a situation adversely affects the position control of the focus lens 103, it is preferable to accurately grasp the amount of backlash. Therefore, in the imaging system 100, the backlash amount is accurately measured by the method described below.

  FIG. 4 is a diagram for explaining the measurement of the backlash amount. Here, FIG. 4A shows a drive pulse input from the motor driver 117 to the motor 101, and FIG. 4B shows a state in which the interchangeable lens 102 is attached to the mount portion Mt to the motor 114. The flowing current value is shown. The vertical axis in FIG. 4B represents the absolute value of the current value.

  First, a drive pulse is input to the motor 114 as in the pulse train Pa shown in FIG. As a result, the motor 114 is rotated by a certain amount in the clockwise direction (CW direction). The current value at this time is a normal current value Ia that flows when the focus lens 103 is actually moving as the motor 114 is driven as shown in FIG.

  Next, a pulse train Pb for rotating the motor 114 in the counterclockwise direction (CCW direction) is input to the motor 114. The pulse train Pb includes a pulse train Pb1 having an acceleration period in which the pulse interval is shorter than that of the pulse train Pa, and a pulse train Pb2 having an equal pulse interval to the pulse train Pa.

  Immediately after the pulse train Pb whose driving direction is reversed is input to the motor 114, due to backlash, a normal current is generated for a certain time from the start of input of the pulse train Pb as in the light load period Tb shown in FIG. A state occurs in which a current value Ib that is significantly smaller than the value Ia and close to “0” flows to the motor 114, that is, a substantially no-load state occurs. Thereafter, the current value of the motor 114 rises.

  Therefore, since the actual backlash amount can be directly detected by measuring the rotation amount of the motor 114 in the light load period Tb, in this embodiment, the light load period Tb is detected by the current value measuring unit 118, and the light load period The amount of backlash is measured by measuring the amount of rotation of the motor 114 during Tb with the encoder 115 and the pulse counter 116.

  As described above, in the imaging system 100, the rotation amount during light load driving, in which the motor 114 is driven with a light load even when the interchangeable lens 102 is mounted, is measured, and the focus lens driving system is related to the measured rotation amount. The backlash amount is acquired, and this specific operation will be described below.

<Operation of Imaging System 100>
FIG. 5 is a flowchart showing the basic operation of the imaging system 100. This operation is executed by the control unit 121.

  When the interchangeable lens 102 is attached to the camera body 101, first, the motor 114 is driven by a certain amount in the CW direction (predetermined displacement direction) (step ST1). Here, a drive pulse is input from the motor driver 117 to the motor 114 as in the pulse train Pa shown in FIG.

  In step ST2, the drive of the motor 114 is stopped after the drive of step ST1.

  In step ST3, the motor 114 is re-driven in the CCW direction that is opposite to the driving direction in step ST1. Here, a drive pulse is input from the motor driver 117 to the motor 114 as in the pulse train Pb shown in FIG.

  In step ST4, it is determined whether the current value of the motor 114 has changed. Specifically, it is determined using the current value measuring unit 118 whether or not the load current of the motor 114 exceeds a predetermined threshold value from the substantially no-load state in the light load period Tb of FIG. If the current value has changed, the process proceeds to step ST5, and if it has not changed, the process returns to step ST3.

  In step ST5, the backlash amount in the drive system of the focus lens 103 is measured. Specifically, the period from the start of re-driving in step ST3 until the motor 114 is driven with a light load until it is determined in step ST4 that the current value of the motor 114 has changed (for example, the light load period Tb in FIG. 4). ) Is measured by the encoder 115 and the pulse counter 116 as a backlash amount.

  In the imaging system 100 described above, the backlash amount of the focus lens drive system is directly measured by measuring the rotation amount during the period when the load current of the motor 114 is substantially “0” when the drive direction is reversed. Therefore, the backlash amount can be measured with high accuracy.

  A smooth AF operation can be realized by using the backlash amount measured with high accuracy in this manner in autofocus (AF) control (particularly when the moving direction of the focus lens 103 is reversed). That is, in the state where the mirror 122 is down and the shutter 124 is closed as shown in FIG. 6A, TTL phase difference detection AF is performed by the AF sensor 123, or as shown in FIG. 6B. When the image AF (contrast AF) based on the contrast of the image obtained by the imaging device 125 capable of acquiring the image related to the subject in the state where the shutter 124 is opened and the shutter 124 is opened, the correction corresponding to the measured backlash amount is performed. By controlling the position of the focus lens 103 in consideration of the amount, the focus lens 103 can be accurately driven. In particular, in contrast AF, which is more accurate than the TTL phase difference detection method and the moving direction of the focus lens 103 is frequently reversed, accurate determination of the backlash amount is effective.

<Modification>
In the above embodiment, it is not always necessary to measure the amount of rotation during the period in which the motor 114 is substantially unloaded as the backlash amount. For example, a current of 20% or less with respect to the peak current value in the motor 114 What is necessary is just to measure the rotation amount at the time of light load which becomes a value.

  As for the focus lens driving motor in the above embodiment, it is not essential to use a DC motor, and a stepping motor or the like may be used. Further, a linear drive actuator may be used.

  In the above embodiment, it is not essential to drive the motor with a constant voltage as shown in FIG. 4A, and it may be driven with a constant current. In addition, as in the above-described embodiment, an acceleration pulse with a short pulse interval is not necessarily required during reverse rotation.

  In the above embodiment, it is not essential to measure the backlash amount when the motor 114 is reversed from the CW direction to the CCW direction, and the backlash amount is measured when the motor 114 is reversed from the CCW direction to the CW direction. Also good. Further, when reversely rotating from the CW direction to the CCW direction, the backlash amount may be measured separately when reversely rotating from the CCW direction to the CW direction.

  The measurement of the backlash amount in the above embodiment is not necessarily performed with a digital camera, and may be performed with a silver salt camera.

  The measurement of the backlash amount in the above embodiment is not essential when the interchangeable lens 102 is attached, and may be performed periodically (every fixed time), for example. Further, the backlash amount may be measured at the following timing.

  (1) Measurement is performed when the imaging system 100 is activated by the main switch 141 with the interchangeable lens 102 mounted.

  As a result, the backlash amount can be measured as a process at the time of start-up, so that the backlash amount is not mistaken even if the lens is exchanged when the power is turned off.

  (2) Measured when the zoom magnification of the interchangeable lens 102 is changed.

  Thereby, since the backlash amount can be measured at the time of zoom change in which the position of the focus lens changes, it is possible to cope with a change in the backlash amount due to a change in the hit of the gear train accompanying the zoom change. However, while the release button 147 is half-pressed (S1 is on), the backlash amount is not measured to prioritize shooting. The presence or absence of the zoom change is determined by the control unit 121 using a zoom encoder in the interchangeable lens 102, for example.

  (3) Measurement is performed when automatic focusing (AF control) using the focus lens 103 is performed.

  As a result, the backlash amount can be measured efficiently and reliably at the time of automatic focusing where there is a high possibility that the moving direction of the focus lens 103 is reversed.

1 is a diagram illustrating an external configuration of an imaging system 100 according to an embodiment of the present invention. 1 is a diagram illustrating an external configuration of an imaging system 100. FIG. It is a conceptual diagram which shows the cross section seen from the III-III position of FIG. It is a figure for demonstrating the measurement of the amount of backlashes. 3 is a flowchart showing a basic operation of the imaging system 100. It is a figure for demonstrating the utilization by AF control of the measured backlash amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Imaging system 101 Camera main body 102 Interchangeable lens 103 Focus lens 104 Lens position change mechanism 114 DC motor 115 Encoder 116 Pulse counter 117 Motor driver 118 Current value measurement part 121 Control part MC Coupler Tb Light load period of a motor

Claims (10)

An image pickup apparatus in which an interchangeable lens having a lens position changing mechanism for changing the position of a focus lens by power input through a coupler can be attached and detached,
(a) an electric actuator that generates the power and can output to the interchangeable lens side through the coupler;
(b) load measuring means for measuring a load related to the electric actuator;
(c) displacement amount measuring means for measuring a displacement amount related to the output of the electric actuator;
(d) a measurement control means for measuring a displacement amount during light load driving in which the electric actuator is driven with a light load even when the interchangeable lens is mounted;
With
An image pickup apparatus, wherein a backlash amount relating to a focus lens driving system including the coupler and the lens position changing mechanism is acquired based on a displacement amount during the light load driving. The imaging device according to claim 1,
The imaging apparatus according to claim 1, wherein the light load is substantially no load. In the imaging device according to claim 1 or 2,
The load measuring means includes
(b-1) means for measuring the load current of the electric actuator as the load;
An imaging device comprising: The imaging apparatus according to any one of claims 1 to 3,
The measurement control means includes
(d-1) first driving means for driving the electric actuator in a predetermined displacement direction;
(d-2) second driving means for stopping driving of the electric actuator after driving by the first driving means and re-driving the electric actuator in a direction opposite to the predetermined displacement direction;
(d-3) means for measuring, by the displacement amount measuring means, a displacement amount during a period of driving with the light load from the start of re-driving by the second driving means, as a displacement amount during the light load driving;
An imaging device comprising: The imaging apparatus according to any one of claims 1 to 4,
The measurement control means includes
(d-4) means for measuring the amount of displacement during light load driving when the interchangeable lens is mounted;
An imaging device comprising: The imaging device according to any one of claims 1 to 5,
The measurement control means includes
(d-5) means for measuring the displacement amount during the light load driving by the displacement amount measuring means at the time of starting the imaging device;
An imaging device comprising: The imaging apparatus according to any one of claims 1 to 6,
The measurement control means includes
(d-6) means for measuring the displacement amount during the light load driving by the displacement amount measuring means at the time of zoom change related to the interchangeable lens;
An imaging device comprising: The imaging device according to any one of claims 1 to 7,
The measurement control means includes
(d-7) means for measuring the amount of displacement during the light load driving by the displacement amount measuring means during automatic focusing using the focus lens;
An imaging device comprising: The imaging apparatus according to any one of claims 1 to 8,
(e) an image sensor capable of acquiring an image related to the subject;
(f) automatic focusing means for performing automatic focusing based on the contrast of the image acquired by the imaging device;
Further comprising
The automatic focusing means performs position control of the focus lens based on the backlash amount. An imaging system having an interchangeable lens and an imaging device to which the interchangeable lens can be attached and detached,
The interchangeable lens is
(a-1) a lens position changing mechanism that changes the position of the focus lens by power input through a coupler;
With
The imaging device
(b-1) an electric actuator that generates the power and can output to the interchangeable lens side via the coupler;
(b-2) load measuring means for measuring a load related to the electric actuator;
(b-3) displacement amount measuring means for measuring the displacement amount related to the output of the electric actuator;
(b-4) a measurement control unit that measures a displacement amount during light load driving in which the electric actuator is driven with a light load even when the interchangeable lens is mounted;
With
An imaging system, wherein a backlash amount relating to a focus lens driving system including the coupler and the lens position changing mechanism is acquired based on a displacement amount during light load driving.

Images