JP2005277765A - Video camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly actuate an auto-focus function even when any exchangeable lens is mounted. <P>SOLUTION: A control means in the camera body acquires the maximum driving speed and the driving delay time from a focus adjusting lens from a mounted exchangeable lens function, inches the focus adjusting lens at the maximum driving speed to drive the focus adjusting lens at a maximum speed at which it can follow up, and, if deciding that the focus adjusting lens cannot have moved within a moving period, based on the maximum driving speed and the driving delay time, reduces the driving quantity of the focus adjusting lens down to a quantity of moving attainable within the moving period, thereby displaying the performance of the mounted exchangeable lens to a maximum to properly actuate the auto-focus function. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a video camera, and is suitable for application to, for example, a broadcast / business digital video camera in which a camera body and an interchangeable lens unit are detachably attached.

  Conventionally, home video cameras are equipped with an autofocus (AF) function that automatically adjusts the focus of the subject by automatically changing the position of the focus adjustment lens according to the distance to the subject. It is possible to accurately focus on the subject without performing manual focus adjustment (see, for example, Patent Document 1).

  Some home video cameras employ a TTL (Through the Lens) hill climbing method. For example, when the focus is greatly out of focus, a high-frequency component included in an imaging signal is extracted and the high-frequency component is extracted. By searching for a location where the level of the component is maximum, an approximate in-focus position can be searched (hereinafter referred to as an overall search).

  For example, as shown in FIG. 7 (A), the home video camera moves the focus adjustment lens from the h2 side, which is one end of the movable range, to the h1 side, which is the other end. / Sequentially generate imaging signals taken every 60 seconds.

  Subsequently, the home video camera extracts a high-frequency component (hereinafter referred to as an evaluation value v) included in each imaging signal, and, for example, two consecutive evaluation values v3 at the positions x3 and x4 of the focus adjustment lens. And v4 are both equal to or greater than a predetermined threshold value vt, and the position x4 where the difference value vd4 is equal to or smaller than the predetermined value is regarded as the vicinity of the maximum value of the evaluation value v, and the position x4 of this focus adjustment lens is the approximate focus position It is made to judge.

  By the way, in home video cameras, if the drive speed of the focus adjustment lens is increased in order to reduce the time for the entire search, the imaging interval is fixed at 1/60 seconds, so that focus adjustment during imaging is performed. Although the position interval of each lens (hereinafter referred to as the total search movement amount ΔX ′) also increases, the characteristic curve of the evaluation value v changes relatively slowly due to the relatively large aperture value and the deep focal depth. Therefore, it is possible to detect without missing the position x4 where the two consecutive evaluation values v3 and v4 are both equal to or larger than the predetermined threshold value vt and the difference vd4 is equal to or smaller than the predetermined value. it can.

  However, in the home video camera, as shown in FIG. 7B, when the aperture value is relatively small and the depth of focus is shallow, the movement speed of the focus adjustment lens is fast and the overall search movement amount ΔX ′ is also large. Depending on the evaluation values v11 to v16, the maximum value cannot be detected, and the approximate focus position is missed.

  Therefore, home video cameras change the moving speed of the focus adjustment lens to the optimum value according to the depth of focus when performing an overall search. For example, as shown in FIG. When the value is small and the depth of focus is shallow, the evaluation value v31 can be detected as a maximum value by decreasing the overall search movement amount ΔX ′ and slowing the movement speed of the focus adjustment lens, and corresponds to the evaluation value v31. The determined position x31 can be recognized as an approximate in-focus position.

  Subsequently, the home video camera moves the focus adjustment lens to the position x31 of the focus adjustment lens determined to be the approximate in-focus position, and then moves the focus adjustment lens around the approximate in-focus position x31. Reciprocate back and forth with a small amplitude (this is called wobbling). The home video camera sequentially acquires the high-frequency component of the imaging signal at the amplitude end of the focus adjustment lens as an evaluation value, and finally focuses on the basis of the acquired evaluation value.

  By the way, the home video camera is configured so that the lens unit cannot be separated from the camera body, so that the operating characteristics such as the maximum driving speed and driving delay of the focus adjustment lens can be handled as fixed values. .

  Therefore, the home video camera can optimize the drive control of the focus adjustment lens in the lens unit based on the operation characteristics, and can search for the in-focus position in a short time.

  By the way, in broadcast / professional video cameras used in television broadcasting stations, skilled professional photographers (so-called cameramen) adjust the focus manually and accurately, so they are equipped with an autofocus function. It wasn't.

In such a broadcast / professional video camera, the camera body and the lens unit (hereinafter referred to as an interchangeable lens unit) are configured to be separable, and the interchangeable lens unit is exchanged at any time to shoot. An interchangeable lens unit suitable for the situation is attached so that an optimal image can be taken.
JP-A-9-33791 (2nd page)

  However, in recent years, BS digital television broadcasting and terrestrial digital television broadcasting adopting high definition image quality (HD: High Definition) with high resolution in addition to conventional analog broadcasting based on standard definition (SD: Standard Definition). Therefore, when the focus cannot be completely adjusted only by focus adjustment relying on the cameraman's visual observation at the time of imaging, the focus shift on the display image becomes conspicuous as compared with the conventional case.

  Therefore, by installing an autofocus function in such a broadcast / professional video camera in the same way as a conventional home video camera, etc., not only relying on the cameraman's focus adjustment but also making full use of the autofocus function. Therefore, a method for accurately adjusting the focus has been proposed.

  However, the interchangeable autofocus lens unit has different operating characteristics of the focus adjustment lens depending on the lens configuration, focal length, zoom magnification, and the like. For this reason, it is difficult to optimize drive control according to the operating characteristics of a focus adjustment lens such as a conventional home video camera in a broadcast / commercial video camera equipped with an interchangeable autofocus lens unit.

  In particular, during the wobbling described above, it is necessary to reciprocate the focus adjustment lens at a high speed and slightly, but depending on the type of the interchangeable autofocus lens unit, the movement of the focus adjustment lens cannot follow the wobbling command. There was a problem that the intended wobbling on the camera side could not be performed.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose a video camera capable of properly functioning an autofocus function even when an arbitrary interchangeable lens unit is attached.

  In order to solve such a problem, the video camera of the present invention is a video camera including a camera body and an interchangeable lens unit detachably attached to the camera body. A diaphragm, a drive means for driving the focus adjustment lens, and a characteristic storage means for storing the maximum drive speed and drive delay time of the focus adjustment lens are provided, and the camera body is provided with focus adjustment via the drive means. In order to recognize the in-focus direction on the imaging surface of the imaging means by minutely driving the lens for imaging, the driving amount of the focus adjustment lens is calculated based on the permissible circle of confusion on the imaging surface and the aperture value of the aperture. Control means for controlling the drive means is provided so that the adjustment lens moves by the drive amount at the maximum drive speed acquired from the characteristic storage means.

  Furthermore, in the video camera of the present invention, the control unit moves the focus adjustment lens to the drive amount within the movement period based on the maximum drive speed and drive delay time acquired from the characteristic storage unit and the calculated drive amount. When it is determined that the focus adjustment lens cannot be used, the drive amount is reduced to such an amount that the focus adjustment lens can move within the movement period.

  This allows the camera body to maximize the performance of the interchangeable lens unit based on the maximum drive speed and drive delay time of the focus adjustment lens, no matter what interchangeable lens unit is mounted. The focus adjustment lens can be finely driven.

  In the lens drive control method of the present invention, the focus adjustment lens of the interchangeable lens unit that is detachably attached to the camera body unit is finely driven by the control unit provided in the camera body unit to A driving amount calculating step for calculating a driving amount of the focus adjustment lens based on an allowable confusion circle diameter on the imaging surface and an aperture value of the interchangeable lens unit in order to recognize a focusing direction on the imaging surface; There is provided a drive control step for moving the lens by a drive amount at the maximum drive speed of the focus adjustment lens acquired from the interchangeable lens unit.

  Furthermore, in the lens drive control method of the present invention, based on the maximum drive speed and drive delay time acquired from the interchangeable lens unit and the calculated drive amount, the focus adjustment lens calculates up to the drive amount calculated within the movement period. When it is determined that the lens cannot be moved, a driving amount reduction step is provided for reducing the driving amount to an amount by which the focus adjustment lens can move within the moving period.

  This makes it possible to maximize the performance of the interchangeable lens unit based on the maximum drive speed and drive delay time of the focus adjustment lens, no matter what interchangeable lens unit is attached to the camera body. The focus adjustment lens can be finely driven.

  In the camera body of the present invention, an interchangeable lens unit having an aperture, a driving unit for driving the focus adjustment lens, and a characteristic storage unit for storing the maximum driving speed and the driving delay time of the focus adjustment lens. In a camera main body unit that is mounted and used, the focus adjustment lens is finely driven through the driving unit to recognize the in-focus direction on the imaging surface of the imaging unit. Control for calculating the driving amount of the focus adjustment lens based on the aperture value and the aperture value of the aperture, and controlling the driving means so that the focus adjustment lens moves by the driving amount at the maximum driving speed acquired from the characteristic storage means Means were provided.

  Further, in the camera main body of the present invention, the control means is configured so that the focus adjustment lens reaches the drive amount within the movement period based on the maximum drive speed and drive delay time acquired from the characteristic storage means and the calculated drive amount. When it is determined that the lens cannot be moved, the driving amount is reduced to an amount that allows the focus adjustment lens to move within the moving period.

  This allows the camera body to maximize the performance of the interchangeable lens unit based on the maximum drive speed and drive delay time of the focus adjustment lens, no matter what interchangeable lens unit is mounted. The focus adjustment lens can be finely driven.

  In the interchangeable lens unit of the present invention, a diaphragm, a drive unit for driving the focus adjustment lens, a characteristic storage unit for storing the maximum drive speed and drive delay time of the focus adjustment lens, and a drive unit are provided. In order to recognize the in-focus direction on the imaging surface of the imaging means provided in the camera body, the camera body calculates the permissible circle of confusion on the imaging surface, the aperture value of the diaphragm, and the maximum drive speed. The focus adjustment lens is driven in accordance with the control signal.

  As a result, the interchangeable lens unit can provide the maximum performance of the focus adjustment lens and the drive delay time to the camera body unit to maximize its performance and drive the focus adjustment lens minutely. .

  According to the present invention, the control unit of the camera body unit obtains the maximum drive speed and drive delay time of the focus adjustment lens from the mounted interchangeable lens unit, and finely drives the focus adjustment lens at the maximum drive speed. When the focus adjustment lens is driven at the maximum speed that can follow, and based on the maximum drive speed and drive delay time, it is determined that the movement of the focus adjustment lens cannot be completed within the movement period. By reducing the drive amount of the focus adjustment lens to such an amount that the lens can move within the movement period, it is possible to maximize the performance of the interchangeable lens unit and allow the autofocus function to function properly.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) Overall Configuration of Video Camera with Autofocus Function In FIGS. 1 and 2, reference numeral 1 denotes a video camera with an autofocus function according to the present invention, which is used for broadcasting and business use that supports HDVS (High Definition Video System) as a whole. The camera body 2 and the interchangeable AF (Auto Focus) lens 3 are detachably attached.

  The camera body 2 is provided with a handle-like grip 4 and a microphone 5 and a viewfinder 6 for collecting sound.

  In the interchangeable AF lens unit 3, a lens for focus adjustment (not shown) is built in the position of the rear lens, and the lens unit 7 having a configuration in which the focus ring 9 is attached to the lens barrel 11, and a user for the focus ring 9 The lens control unit 8 is used to adjust the focus by moving the focus adjustment lens in response to the operation. A hood 12 is attached to the lens unit 7.

  The lens control unit 8 of the interchangeable AF lens unit 3 is supplied with power from the camera body 2 while attached to the camera body 2, and performs focus adjustment and the like based on the power. Has been made.

  In the video camera 1 with an autofocus function having such a configuration, the interchangeable AF lens unit 3 can be detachably removed. Therefore, another interchangeable AF lens unit having a zoom ratio different from that of the interchangeable AF lens unit 3 is used. It can be easily exchanged for use.

  In the video camera 1 with an autofocus function, the lens control unit 8 of the interchangeable AF lens unit 3 is provided with a changeover switch 10 for alternately switching between the autofocus mode and the manual focus mode. The auto focus mode and the manual focus mode can be switched according to the situation.

  In the video camera 1 with an autofocus function, when the autofocus mode is set, the focus adjustment is automatically performed under the control of the lens control unit 8, but the manual focus mode is set. In some cases, focus adjustment is performed by moving a focus adjustment lens (not shown) built in the interchangeable AF lens unit 3 in accordance with a rotation operation of the focus ring 9 by a cameraman.

  By the way, the video camera 1 with autofocus function is HDVS compatible and the image quality is much clearer than the conventional SD (Standard Definition) method, so it can be prevented from appearing in the image even if it is slightly out of focus. Therefore, an autofocus function for correcting a cameraman's focus adjustment operation is provided even in the manual focus mode.

(2) Circuit Configuration of Video Camera 1 with Autofocus Function As shown in FIG. 3, the video camera 1 with an autofocus function has a lens mount (not shown) with an interchangeable AF lens unit 3 with respect to the camera body unit 2. Is attached via the electrical connection point 30, a communication path 31 is formed between the camera body 2 and the replaceable AF lens unit 3.

  The camera body 2 controls the focus and aperture value of the solid-state image sensor 27, the signal processor 28 that performs predetermined signal processing on the image signal obtained by the solid-state image sensor 27, and the interchangeable AF lens unit 3. The control unit 29 is provided.

  On the other hand, the interchangeable AF lens unit 3 includes a front group 21 and a rear group 22 each composed of a plurality of lenses, and a diaphragm 23 provided between the front group 21 and the rear group 22. The interchangeable AF lens unit 3 is a rear focus type, and one lens in the rear group 22 is a focus adjustment lens 22A. The focus adjustment lens 22A also serves as a wobbling lens.

  The lens controller 26 of the interchangeable AF lens unit 3 drives the focus motor 24 according to the focus control signal Sf and the wobbling control signal Sw supplied from the control unit 29 to move the focus adjustment lens 22A in the direction of the arrow h1 or h2. The diaphragm motor 25 is driven in accordance with the diaphragm control signal Si to control the opening degree (that is, the diaphragm value) of the diaphragm 23.

  The focus motor 24 is a stepping motor. Therefore, the focus control signal Sf and the wobbling control signal Sw supplied from the control unit 29 specify how many steps (that is, the rotation speed) the focus motor 24 rotates per second. It is given in units of [pps] (Pulse Per Sec).

  Further, the camera body 2 captures the subject image formed on the imaging surface of the solid-state image sensor 27 by the interchangeable AF lens unit 3 with the solid-state image sensor 27 to generate an image signal, and generates the image signal. To enter. The AF detection unit 28 </ b> A of the signal processing unit 28 extracts a high frequency component of the imaging signal and sends the extraction result to the control unit 29.

  The control unit 29 is premised on a TTL (Through the Lens) hill-climbing method, and extracts the level of the high-frequency component of the imaging signal obtained from the solid-state imaging device 26 at a 1/60 second period corresponding to the field period as an evaluation value. By determining that the in-focus point exists in the direction h1 or h2 in which the level of the high-frequency component of the imaging signal becomes larger, the in-focus direction can be recognized.

  As a result, the control unit 29 finally sets the focus adjustment lens 22A to an appropriate one based on the result of recognizing which direction h1 or h2 moves from the current position of the focus adjustment lens 22A. The in-focus state is obtained by driving at a feeding speed.

(3) Focus Adjustment Processing Procedure First, an outline of the focus adjustment processing in the video camera 1 with an autofocus function will be described using the flowchart shown in FIG.

  The video camera 1 with an autofocus function enters from the start step of the focus adjustment processing routine RT1 and proceeds to the next step SP1, and first recognizes the in-focus direction by wobbling the focus adjustment lens 22A.

  At this time, in the video camera 1 with an autofocus function, when the focus adjustment lens 22A exists at a position far from the focus position and the focus direction cannot be recognized at all, the process proceeds to the next step SP2, and the focus adjustment lens 22A is used. After searching the whole where the approximate in-focus position exists within the movable range in which the lens 22A can move, the process proceeds to the next step SP3.

  Incidentally, when the in-focus video camera 1 can recognize the in-focus direction in step SP1, it directly moves to step SP4 and finally searches for the in-focus position.

  In step SP3, the video camera with an autofocus function 1 searches for an approximate in-focus position by the overall search, and then recognizes the in-focus direction by driving the focus adjustment lens 22A again to move to the next step SP4. .

  In step SP4, the video camera 1 with an autofocus function finally searches for the in-focus position, and by positioning the focus adjustment lens 22A at the in-focus position, the subject is focused so that there is no slight defocus. The focus adjustment processing procedure is completed by matching.

  Furthermore, the video camera 1 with an autofocus function monitors the in-focus state even after the subject is in focus, and when the subject is out of focus, the focus adjustment processing procedure described above is executed again so that the subject is always in focus. It is made to keep matching.

(4) Control of wobbling amount according to aperture value The amount of movement of the focus adjustment lens 22A during wobbling is closely related to the allowable circle of confusion and the depth of focus. In general, light passing through a lens forms a point image on the focal plane. This point image is a circle having a certain diameter, and this is also called a blurred circle. The smaller the diameter of this blur circle, the sharper the focus is recognized with the naked eye. The diameter is the allowable circle of confusion circle d. The permissible circle of confusion d is also a value uniquely determined by the resolution of the optical system and the solid-state image sensor 27.

  On the other hand, when focusing on a subject, the objects before and after the focused subject are clearly visible to the extent that they can be used practically. On the focal side, there is a range where a clear image is formed before and after the focal point, and this is the focal depth 2Δx.

  When the sum of the defocus amounts on the front side and the rear side when the blur within the perceptual limit occurs is 2Δx, if the lens aberration is ignored, the defocus amount Δx is equal to the allowable confusion circle diameter d and the aperture 23. Based on the aperture value Fn, it can be calculated using the following equation.

  Δx = d · Fn (1)

  Therefore, if the focus adjustment lens 22A is reciprocated with a movement amount that is less than the movement amount defocus amount Δx, the wobbling can be performed without the user perceiving the defocusing.

  That is, the lens controller 26 uses the following equation based on the allowable circle of confusion diameter d and the focal point movement coefficient a given from the camera body and the aperture value Fn of the aperture 23.

  Δx ′ = d · Fn · a (0 <a <1) (2)

Is calculated as follows. Here, the focus movement coefficient a is a value arbitrarily determined in the range of 0 <a <1, and the blurring circle is suppressed to be less than the allowable confusion circle by suppressing the focal movement amount Δx ′ to be less than the defocus amount Δx. The focus shift coefficient a is determined by the control unit 29 of the camera body 2 and is commanded to the lens side as the wobbling control signal Sw. .

  Then, the control unit 29 supplies the value a as a wobbling control signal to the lens controller 26 of the interchangeable AF lens unit 3, and the lens controller 26 calculates the focal movement amount Δx ′ and controls the lens. Wobbling is performed without being perceived by the photographer.

(5) Control of wobbling amount and speed according to operation characteristics of interchangeable AF lens unit As described above, the video camera 1 with an autofocus function can be detachably removed from the replaceable AF lens unit 3. Therefore, it is possible to shoot with an optional interchangeable AF lens unit 3 attached according to the shooting situation.

  Here, as shown in FIG. 3, the lens controller 26 of the interchangeable AF lens unit 3 is provided with a characteristic storage unit 26 </ b> A that stores the operation characteristic Smv unique to the focus adjustment lens 22 </ b> A of the interchangeable AF lens unit 3. ing. The contents of the operation characteristic Smv are the maximum drive speed Vmax [pps] of the focus motor 24 corresponding to the maximum speed that the focus adjustment lens 22A can follow and the drive delay time Td [s] of the focus adjustment lens 22A. Become.

  Then, the camera body 2 of the video camera 1 with an autofocus function acquires the above-described operation characteristic Smv from the mounted interchangeable AF lens unit 3, and the acquired operation characteristic Smv and the aperture value of the aperture 23 at that time Based on Fn, the wobbling control signal Sw is generated so as to drive the focus adjustment lens 22A with an optimum driving amount for the mounted interchangeable AF lens unit 3.

  Next, an example of wobbling control according to the operation characteristic Smv of the replaceable AF lens unit 3 described above will be described in detail with reference to timing charts shown in FIGS. This video camera 1 with an autofocus function is an interlace system, and the focus adjustment lens 22A is moved by a predetermined amount (wobbling) in a certain field (odd field in the example shown in FIGS. 4 and 5). The in-focus direction is determined by repeatedly acquiring the high-frequency component level of the imaging signal as an evaluation value in the even field, and thus the video camera 1 with an autofocus function performs wobbling control in units of one frame. ing.

  FIG. 4 shows an example of the interchangeable AF lens unit 3 having relatively high operating characteristics, and the maximum driving speed Vmax is set to 2000 [pps]. The wobbling drive amount Wb when the aperture value Fn = 1.6 is 1 step (amplitude is 2 steps), and the wobbling drive amount Wb when the aperture value Fn is slightly greater than 5.6 is 4 steps (amplitude is 8 steps). When the aperture value Fn = 16, the wobbling drive amount Wb is 8 steps (amplitude is 16 steps).

  As described above, in the wobbling control, the wobbling drive amount Wb increases as the lens aperture value increases, and the moving time of the focus adjustment lens 22A also increases. However, in the example shown in FIG. 4, since the maximum drive speed Vmax is high and the drive delay time Td is also relatively short, the most severe conditions (the wobbling drive amount is large and the movement time is long) the aperture value Fn Even when = 16, the focus adjustment lens 22A can complete the movement in the odd field.

  On the other hand, FIG. 5 shows an example of the interchangeable AF lens unit 3 having a relatively low speed operation characteristic, and the maximum drive speed Vmax is set to 800 [pps]. The relationship between the aperture value Fn and the wobbling drive amount is the same as in the example of FIG. 5, and the wobbling amount Wb when the aperture value Fn = 1.6 is 1 step, and the wobbling drive amount when the aperture value Fn = 5.6 or more. Wb is 4 steps, and the wobbling drive amount Wb when the aperture value Fn = 16 is 8 steps.

  In the example shown in FIG. 5, since the maximum drive speed Vmax is low and the drive delay time Td is also relatively long, the focus adjustment lens 22A is in the odd field when the most severe aperture value Fn = 16. In this case, the movement cannot be completed and the even field is shifted to, so that the evaluation value of the high frequency component level obtained in the even field becomes an unreliable value.

  For this reason, the control unit 28 performs wobbling so that the focus adjustment lens 22A completes the movement within the odd field set as the movement period of the focus adjustment lens 22A based on the maximum drive speed Vmax and the drive delay time Td. The drive amount Wb is reduced. Alternatively, the wobbling period is changed so that wobbling is performed with a period longer than one frame unit in order to ensure a time during which the movement target position can be reached.

  A series of these processes will be described in detail with reference to the flowchart of FIG. The control unit 29 of the camera body unit 2 enters from the start step of the wobbling control processing routine RT2 and moves to the next step SP11, and acquires the operation characteristic Smv from the characteristic storage unit 26A of the exchangeable AF lens unit 3 attached. Then, the process proceeds to the next step SP12.

  In step SP12, the control unit 29 calculates the wobbling drive amount Wb based on the current aperture value Fn of the aperture 23, and proceeds to the next step SP13.

  In step SP13, the control unit 29 determines that the focus adjustment lens 22A is within the odd field based on the calculated wobbling drive amount Wb, the maximum drive speed Vmax [pps] and the drive delay time Td [s] of the acquired operation characteristic Smv. To judge whether or not the movement is completed. When it is determined in step SP13 that the focus adjustment lens 22A has been moved within the odd field, the control unit 29 proceeds to the next step SP14.

  On the other hand, if it is determined in step SP13 that the focus adjustment lens 22A cannot be moved within the odd field, the control unit 29 moves to step SP15 and the focus adjustment lens 22A is moved within the odd field. After correcting (reducing) the wobbling drive amount Wb as described above, the process proceeds to step SP14. Alternatively, the wobbling period is changed so as to perform wobbling with a period longer than one frame unit in order to secure the time for reaching the movement target position without changing the driving amount Wb, and the process proceeds to step SP14.

  In step SP14, the control unit 29 generates a wobbling control signal Sw such that the focus adjustment lens 22A moves to the wobbling driving amount Wb at the maximum driving speed Vmax [pps], and supplies the wobbling control signal Sw to the interchangeable AF lens unit 3. Then, the process proceeds to the next step SP16.

  In step SP16, the control unit 29 acquires the high-frequency component level of the imaging signal obtained in the next even field period as an evaluation value, and then returns to step SP11 and repeats steps SP12 to SP16 again in units of one frame. Wobbling is performed to determine the in-focus direction.

(6) Operation and Effect In the above configuration, the camera body 2 of the video camera 1 with an autofocus function obtains the operation characteristic Smv of the focus adjustment lens 22A from the characteristic storage unit 26A of the interchangeable AF lens unit 3 attached. get.

  Then, the control unit 29 of the camera main body 2 determines the maximum speed at which the focus adjustment lens 22A can be followed based on the acquired maximum driving speed Vmax of the operating characteristic Smv and the aperture value Fn of the interchangeable AF lens unit 3 at that time. Wobble with.

  Further, at this time, the control unit 29 moves the focus adjustment lens 22A based on the acquired maximum driving speed Vmax and driving delay time Td of the operating characteristic Smv and the aperture value Fn of the interchangeable AF lens unit 3 at that time. The wobbling drive amount Wb is corrected so that the focus adjustment lens 22A completes the movement within the odd field. Alternatively, the wobbling period is changed so that the wobbling is performed in a period longer than one frame unit in order to secure the reachable time with the driving amount Wb as it is.

  As a result, the camera body unit 2 can obtain the operating characteristic Smv of the focus adjustment lens 22A from the interchangeable AF lens unit 3 regardless of what type of interchangeable AF lens unit 3 is mounted. The wobbling can be performed by maximizing the performance of the interchangeable AF lens unit 3.

  According to the above configuration, the video camera 1 with an autofocus function can be used even when the interchangeable AF lens unit 3 having any lens characteristics is mounted on the camera body 2. It is possible to perform the wobbling by maximizing the performance of No. 3, and to properly function the autofocus function.

(7) Other Embodiments In the above-described embodiment, the case where the focus adjustment lens 22A is wobbled in the odd field and the evaluation value is acquired in the next even field has been described. Not limited to this, the focus adjustment lens 22A may be wobbled in the even field, and the evaluation value may be acquired in the next odd field. Further, when the performance of the focus motor 24 and the lens drive system is improved, the maximum drive speed Vmax of the focus adjustment lens 22A and the drive delay time Td are shortened. May be executed within one field.

  In the above-described embodiment, the case where the operation characteristic Smv of the focus adjustment lens 22A is sent to the control unit 29 of the camera body 2 via the electrical connection point 30 and the communication path 31 has been described. However, the present invention is not limited to this, and it may be transmitted to the control unit 29 of the camera body 2 by a wireless communication method such as Bluetooth communication method or IEEE (Institute of Electrical and Electronics Engineers) 802.11g.

  In the above-described embodiment, the case where the rear focus type interchangeable AF lens unit 3 is used has been described. However, the present invention is not limited to this, and the replaceable AF lens unit 3 having various lens configurations such as a front focus. May be used.

  Furthermore, in the above-described embodiment, the case where the focus adjustment lens 22A uses the interchangeable AF lens unit 3 configured to also serve as a wobbling lens has been described. However, the present invention is not limited to this, and the focus adjustment lens and wobbling are used. You may use the exchangeable AF lens part 3 of the structure which has a lens separately.

  Furthermore, in the above-described embodiment, the case where a stepping motor is used as the focus motor 24 has been described. However, the present invention is not limited to this, and other various motors such as a coreless motor and an ultrasonic motor can be used as the focus motor 24. It may be used. In this case, it is necessary to appropriately select the speed instruction unit (for example, [rpm] (Revolution Per Sec)) of the focus control signal Sf and the wobbling control signal Sw according to the type of the motor.

  The video camera of the present invention can also be applied to a home video camera or a surveillance video camera to which an interchangeable AF lens can be attached.

It is a rough-line perspective view which shows the external appearance structure of the video camera with an autofocus function of this invention. It is a basic diagram which shows the side surface structure of a video camera with an autofocus function. It is a basic block diagram which shows the circuit structure of the video camera with an autofocus function. It is a flowchart which shows a focus adjustment processing procedure. It is a timing chart with which it uses for description of wobbling when an operation characteristic is high speed. It is a timing chart with which it uses for description of wobbling when an operation characteristic is low speed. It is a flowchart which shows a wobbling control processing procedure. It is a basic diagram with which it uses for description of the mode of the whole search of an in-focus position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Video camera with an autofocus function, 2 ... Camera body part, 3 ... Interchangeable AF lens part, 21 ... Front group, 22 ... Rear group, 22A ... Focus adjustment lens, 23 ... Aperture , 24... Focus motor, 25... Aperture motor, 26... Lens controller, 27... CCD, 28.

Claims (7)

A video camera comprising a camera body and an interchangeable lens part detachably attached to the camera body,
The interchangeable lens unit includes a diaphragm, a drive unit that drives the focus adjustment lens, and a characteristic storage unit that stores a maximum drive speed and a drive delay time of the focus adjustment lens,
In the camera body, the focus adjustment lens is finely driven through the driving means to recognize the in-focus direction on the imaging surface of the imaging means. Control means for calculating the drive amount of the focus adjustment lens based on the value and controlling the drive means so that the focus adjustment lens moves by the drive amount at the maximum drive speed acquired from the characteristic storage means A video camera characterized by comprising If the focus adjustment lens cannot move to the drive amount within the movement period based on the maximum drive speed and the drive delay time acquired from the characteristic storage unit and the calculated drive amount, the control means The video camera according to claim 1, wherein when the determination is made, the driving amount is reduced to an amount by which the focus adjustment lens can move within the moving period. In order to recognize the in-focus direction on the imaging surface of the imaging means by minutely driving the focus adjustment lens of the interchangeable lens unit provided detachably with the camera body by the control unit provided in the camera body. A drive amount calculation step of calculating a drive amount of the focus adjustment lens based on an allowable confusion circle diameter on the imaging surface and an aperture value of the interchangeable lens unit;
A lens drive control method comprising: a drive control step of moving the focus adjustment lens by the drive amount at a maximum drive speed of the focus adjustment lens acquired from the interchangeable lens unit. When it is determined that the focus adjustment lens cannot move to the driving amount within the moving period based on the maximum driving speed and the driving delay time acquired from the interchangeable lens unit and the calculated driving amount. The lens drive control method according to claim 3, further comprising a drive amount reduction step of reducing the drive amount to an amount by which the focus adjustment lens can move within the movement period. An interchangeable lens unit having a diaphragm, a driving unit that drives the focus adjustment lens, and a characteristic storage unit that stores the maximum drive speed and the drive delay time of the focus adjustment lens is mounted and used. In the camera body,
Focus adjustment based on the permissible circle of confusion on the imaging surface and the aperture value of the diaphragm so as to recognize the in-focus direction on the imaging surface of the imaging unit by minutely driving the focus adjustment lens via the driving unit And a control means for controlling the drive means so that the focus adjustment lens moves by the drive amount at the maximum drive speed acquired from the characteristic storage means. The camera body. If the focus adjustment lens cannot move to the drive amount within the movement period based on the maximum drive speed and the drive delay time acquired from the characteristic storage unit and the calculated drive amount, the control means 6. The camera body according to claim 5, wherein when the determination is made, the drive amount is reduced to an amount by which the focus adjustment lens can move within the movement period. Aperture,
Driving means for driving the focus adjustment lens;
Characteristic storage means for storing the maximum drive speed and drive delay time of the focus adjustment lens,
The drive means recognizes the in-focus direction on the image pickup surface of the image pickup means provided in the camera body, and is based on the allowable confusion circle diameter on the image pickup surface, the aperture value of the stop, and the maximum drive speed. The interchangeable lens unit, wherein the focus adjustment lens is driven according to a control signal calculated by the camera body unit.

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