JP4438427B2 - Video camera and in-focus direction determination method - Google Patents

Description

The present invention relates to a video camera and an in-focus direction determination method , and is suitably applied to, for example, a broadcast / business digital video camera in which a camera body and an interchangeable lens 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. 10 (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. 10B, when the aperture value is relatively small and the focal depth is shallow, similarly, the movement speed of the focus adjustment lens is fast and the total search movement amount ΔX ′ is 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 are configured to change the moving speed of the focus adjustment lens to the optimum value according to the depth of focus when performing the whole 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 focus position, and finally adjusts the focus by performing predetermined fine adjustment. It is made like that.

  By the way, the home video camera is configured so that the lens unit cannot be separated from the camera body. Therefore, the movable range of the focus adjustment lens of the lens unit and the response characteristics of the actuator that drives the focus adjustment lens Etc. (hereinafter referred to as “lens parameters”) can be treated as fixed values.

  Therefore, in a home video camera, it is possible to optimally perform drive control of the focus adjustment lens in the lens unit based on this lens parameter, and to search for the in-focus position in a short time.

  By the way, in broadcast / professional video cameras used in television broadcasting stations, a professional photographer (so-called cameraman) manually adjusts the focus manually, so it does not have an autofocus function. It was.

In such a broadcast / professional video camera, the camera main body and the lens (hereinafter referred to as an interchangeable lens) are configured to be separable, and the interchangeable lens is used as needed. In various situations, an optimum image can be taken using an optimum interchangeable lens unit.
JP-A-9-33791 (2nd page)

  In recent years, however, BS digital television broadcasting and terrestrial digital television that employ high definition image quality (HD: High Definition) with high resolution in addition to terrestrial analog broadcasting based on standard definition (SD) standard definition. Since broadcasting has started, when focusing with a cameraman's visual observation when shooting with a broadcast / professional video camera was not possible to achieve complete focus, the out-of-focus image was clear. Will be displayed.

  Therefore, by installing an autofocus function in such broadcast and commercial video cameras as well as conventional home video cameras, the autofocus function is utilized not only by the cameraman's focus adjustment. A method for accurately adjusting the focus has been proposed.

  However, in a broadcast / professional video camera using an interchangeable lens unit, when various types of interchangeable autofocus (AF) lens units are mounted, the lens parameters of each interchangeable AF lens unit are different. There is a problem in that the original autofocus function cannot be exhibited correctly unless the difference in lens parameters is absorbed by the camera body.

The present invention has been made in consideration of the above points, and it is possible to accurately determine the in-focus direction so that the autofocus function can be properly functioned even when an optional interchangeable lens unit is mounted. It is intended to propose a video camera and a focusing direction determination method that can be accurately matched.

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 drive unit for driving the focus adjustment lens, a drive amount calculation unit for calculating the drive amount of the focus adjustment lens, and a diaphragm are provided. The camera body has a small amount of focus adjustment lens via the drive unit. In order to determine the amount of focus movement for driving and recognizing the in-focus direction on the imaging surface of the imaging means, the permissible circle of confusion on the imaging surface and the first ratio to the depth of focus are calculated as the drive amount of the interchangeable lens unit. supplied to means, when it can not recognize the focusing direction even when is minutely drives the focus adjustment lens by driving means in accordance with the focal shift amount, a focus adjustment In order to obtain an overall search movement amount for searching for an approximate in-focus position by sequentially moving the lens within the movable range, the permissible circle of confusion and the focal depth which is a value larger than the first ratio are determined. comprising a control means for supplying to the interchangeable lens unit of the driving amount calculation unit and the second ratio, the driving amount calculation unit of the interchangeable lens unit, the relative permissible circle of confusion and the depth of focus is supplied from the control unit 1 the ratio of to calculate the focus movement amount of the focus adjustment lens based on a diaphragm aperture value, or a second ratio permissible circle of confusion and the depth of focus is supplied from the control unit, a diaphragm aperture value calculates the overall search movement amount of the focus adjusting lens based on the driving means, a focus adjusting lens in accordance with the focal shift amount in order to recognize the focusing direction is minutely driven, or the overall search movement The focus adjustment lens is moved in accordance with the control unit, and the control unit of the camera body determines an approximate in-focus position based on the evaluation value for the imaging signal obtained from the imaging unit via the focus adjustment lens at that time. After that, the permissible circle of confusion and the first ratio with respect to the depth of focus are supplied again to the drive amount calculation means, and the focus adjustment lens is approximated by the drive means by the drive means in accordance with the focus movement amount obtained as a result. When the evaluation value is obtained when the final in-focus direction is determined by minute driving from the evaluation value, and the evaluation value is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or smaller than the predetermined value The final positioning is performed with the position of the focus adjustment lens as an accurate in-focus position .

Thereby , even when the focus adjustment lens is finely driven in accordance with the focal distance calculated based on the permissible circle of confusion on the imaging surface, the first ratio with respect to the depth of focus, and the aperture value of the aperture, the in-focus direction can be set. If it cannot be recognized, the approximate in-focus position is quickly determined according to the entire search movement amount calculated based on the permissible circle of confusion, the second ratio with respect to the depth of focus greater than the first ratio, and the aperture value. The final focus direction is determined by finely driving the focus adjustment lens from the approximate focus position in accordance with the focus movement amount calculated again based on the permissible circle of confusion and the first ratio with respect to the focus depth. If the evaluation value is equal to or higher than a predetermined threshold and the difference from the previous evaluation value is equal to or lower than the predetermined value, the evaluation value is obtained. The position of the focus adjustment lens can make the final positioning as an accurate focus position of when.

In the in-focus direction determining method according to the present invention, the control unit provided in the camera main body part finely moves the focus adjustment lens of the interchangeable lens part that is detachably provided from the camera main body part. In order to obtain a focus movement amount for recognizing the in-focus direction on the imaging surface, an allowable confusion circle diameter on the imaging surface and a first ratio with respect to the depth of focus are calculated from the control unit as a drive amount calculation unit for the interchangeable lens unit. a first data supplying step of supplying to the, by the driving amount calculation means, based a first ratio permissible circle of confusion and the depth of focus is supplied from the control means, to the aperture value of the aperture in the interchangeable lens unit calculating a focus moving amount of the focus adjustment lens Te, fine driving system for finely driving the focusing lens in accordance with the focal shift amount for recognizing if Asekata direction A step, when it can not recognize the focusing direction by the minute driving control step for searching an approximate focus position by sequentially moving the focus adjustment lens via the drive means of the camera body within a movable range In order to obtain the total search movement amount, the control means supplies the permissible circle of confusion diameter and the second ratio to the depth of focus, which is a value larger than the first ratio, from the control means to the drive amount calculation means of the interchangeable lens unit. The entire search movement amount of the focus adjustment lens is calculated based on the permissible circle of confusion, the second ratio with respect to the depth of focus, and the aperture value of the diaphragm by the data supply step 2 and the drive amount calculation means, An in-focus position acquisition step for obtaining an approximate in-focus position by moving the focus adjustment lens by the driving means in accordance with the search movement amount; and a control means The focus movement amount of the focus adjustment lens is calculated based on the permissible circle of confusion supplied again, the first ratio to the depth of focus, and the aperture value, and the focus adjustment lens is calculated according to the focus movement amount. A focus direction determination step for determining the final focus direction by micro-driving the lens from the approximate focus position, and an evaluation value for the image signal obtained from the image pickup means via the focus adjustment lens at that time When the difference from the previous evaluation value is less than or equal to a predetermined value that is equal to or greater than a predetermined threshold value, the final positioning is performed with the position of the focus adjustment lens when the evaluation value is obtained as an accurate in-focus position. A positioning step to be performed .

Thereby , even when the focus adjustment lens is finely driven in accordance with the focal distance calculated based on the permissible circle of confusion on the imaging surface, the first ratio with respect to the depth of focus, and the aperture value of the aperture, the in-focus direction can be set. If it cannot be recognized, the approximate in-focus position is quickly determined according to the entire search movement amount calculated based on the permissible circle of confusion, the second ratio with respect to the depth of focus greater than the first ratio, and the aperture value. The final focus direction is determined by finely driving the focus adjustment lens from the approximate focus position in accordance with the focus movement amount calculated again based on the permissible circle of confusion and the first ratio with respect to the focus depth. If the evaluation value is equal to or higher than a predetermined threshold and the difference from the previous evaluation value is equal to or lower than the predetermined value, the evaluation value is obtained. The position of the focus adjustment lens can make the final positioning as an accurate focus position of when.

Furthermore, the video camera of the present invention is a video camera comprising a camera main body and an interchangeable lens unit that is detachably attached to the camera main body, and the focus adjustment lens is provided on the interchangeable lens unit. A driving unit for driving and a driving amount calculating unit for calculating a driving amount of the focus adjustment lens, and the camera main body is driven by the driving unit to finely drive the focus adjustment lens to thereby capture the imaging surface of the imaging unit. to determine the focus movement amount for recognizing the focusing direction in a permissible circle of confusion on the imaging plane, a first ratio of the focal depth, the driving amount calculation unit of the interchangeable lens unit and the aperture of the aperture supplied, when it can not recognize the focusing direction even when is minutely drives the focus adjustment lens by driving means in accordance with the focal shift amount, shifting the focus adjusting lens In order to obtain an overall search movement amount for searching for an approximate in-focus position by sequentially moving within a possible range, a second value with respect to the permissible circle of confusion diameter and a focal depth that is larger than the first ratio is obtained. the ratio, comprising a control means for supplying to said driving amount calculation unit of the interchangeable lens unit and the aperture value, the drive amount calculating device of the interchangeable lens unit, and the permissible circle of confusion that is supplied from the control means, the depth of focus Calculating the amount of focal movement of the focus adjustment lens based on the first ratio to the aperture and the aperture value of the diaphragm , or the allowable confusion circle diameter supplied from the control means, and the second ratio to the focal depth, based on the diaphragm aperture value to calculate the overall search movement amount of the focus adjustment lens, driving means, the focus adjustment lens according to the focus movement amount in order to recognize the focusing direction is minutely driven, or the entire probe The focus adjustment lens is moved in accordance with the amount of movement, and the control means of the camera body unit is configured to obtain an approximate in-focus position based on an evaluation value with respect to the imaging signal obtained from the imaging means via the focus adjustment lens at that time. Then, the permissible circle of confusion, the first ratio to the depth of focus, and the aperture value of the aperture are supplied again to the drive amount calculation means, and the focus adjustment is performed by the drive means according to the focus movement amount obtained as a result. When the final focusing direction is determined by micro-driving the objective lens from the approximate focus position, and the evaluation value is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or less than the predetermined value The final positioning is performed by setting the position of the focus adjustment lens when the evaluation value is obtained as an accurate in-focus position .

Thereby , even when the focus adjustment lens is finely driven in accordance with the focal distance calculated based on the permissible circle of confusion on the imaging surface, the first ratio with respect to the depth of focus, and the aperture value of the aperture, the in-focus direction can be set. If it cannot be recognized, the approximate in-focus position is quickly determined according to the entire search movement amount calculated based on the permissible circle of confusion, the second ratio with respect to the depth of focus greater than the first ratio, and the aperture value. The final focus direction is determined by finely driving the focus adjustment lens from the approximate focus position in accordance with the focus movement amount calculated again based on the permissible circle of confusion and the first ratio with respect to the focus depth. If the evaluation value is equal to or higher than a predetermined threshold and the difference from the previous evaluation value is equal to or lower than the predetermined value, the evaluation value is obtained. The position of the focus adjustment lens can make the final positioning as an accurate focus position of when.

In the in-focus direction determining method according to the present invention, the control unit provided in the camera main body part finely moves the focus adjustment lens of the interchangeable lens part that is detachably provided from the camera main body part. In order to obtain the amount of focus movement for recognizing the in-focus direction on the image pickup surface, the permissible circle of confusion on the image pickup surface, the first ratio to the depth of focus, and the aperture value of the stop are interchangeable from the control unit. a first data supply step of supplying to the driving amount calculation means parts by the driving amount calculation means, and permissible circle of confusion that is supplied from the control unit, a first ratio of the depth of focus, on the basis of the aperture value calculating a focus moving amount of the focus adjustment lens, and the minute driving control step of finely driving the focusing lens in accordance with the focal shift amount for recognizing if Asekata direction, microcrystalline When the focus control direction cannot be recognized by the drive control step, the entire search movement for searching the approximate focus position is performed by sequentially moving the focus adjustment lens within the movable range via the drive means of the camera body. In order to obtain the amount, the permissible circle of confusion, the second ratio with respect to the depth of focus, which is a value larger than the first ratio, and the aperture value of the stop are supplied from the control means to the drive amount calculation means of the interchangeable lens unit. The entire search movement amount of the focus adjustment lens is calculated based on the permissible circle of confusion, the second ratio with respect to the focal depth, and the aperture value by the second data supply step and the driving amount calculation means. An in-focus position acquisition step for obtaining an approximate in-focus position by moving the focus adjustment lens by the driving means according to the search movement amount; A focus movement amount of the focus adjustment lens is calculated based on the supplied permissible circle of confusion, the first ratio with respect to the depth of focus, and the aperture value of the stop, and the focus adjustment lens according to the focus movement amount A focus direction determination step for determining the final focus direction by micro-driving the lens from the approximate focus position, and an evaluation value for the image signal obtained from the image pickup means via the focus adjustment lens at that time When the difference from the previous evaluation value is less than or equal to a predetermined value that is equal to or greater than a predetermined threshold value, the final positioning is performed with the position of the focus adjustment lens when the evaluation value is obtained as an accurate in-focus position. A positioning step to be performed .

Thereby , even when the focus adjustment lens is finely driven in accordance with the focal distance calculated based on the permissible circle of confusion on the imaging surface, the first ratio with respect to the depth of focus, and the aperture value of the aperture, the in-focus direction can be set. If it cannot be recognized, an approximate in-focus position is quickly determined according to the entire search movement amount calculated based on the permissible circle of confusion, the second ratio with respect to the focal depth greater than the first ratio, and the aperture value. The final focus direction is determined by finely driving the focus adjustment lens from the approximate focus position in accordance with the focus movement amount calculated again based on the permissible circle of confusion and the first ratio with respect to the focus depth. If the evaluation value is equal to or higher than a predetermined threshold and the difference from the previous evaluation value is equal to or lower than the predetermined value, the evaluation value is obtained. The position of the focus adjustment lens can make the final positioning as an accurate focus position of when.

According to the present invention, even when the focus adjustment lens is micro-driven in accordance with the focal distance calculated based on the allowable confusion circle diameter on the imaging surface , the first ratio to the focal depth, and the aperture value of the diaphragm. If the focal direction cannot be recognized, the approximate search speed is quickly determined according to the total search movement amount calculated based on the permissible circle of confusion, the second ratio with respect to the depth of focus greater than the first ratio, and the aperture value. The focus position is obtained, and the focus adjustment lens is finely driven from the approximate focus position according to the focus movement amount calculated again based on the permissible circle of confusion and the first ratio with respect to the focus depth. When the focus direction can be determined accurately and in a short time, and the evaluation value is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or less than the predetermined value, the evaluation value The resulting position of the focus adjustment lens when the it is possible to realize a video camera capable of performing final positioning as an accurate focus position.

Further, according to the present invention, even when the focus adjustment lens is micro-driven in accordance with the focal distance calculated based on the permissible circle of confusion on the imaging surface , the first ratio to the focal depth, and the aperture value of the diaphragm. When the in-focus direction cannot be recognized, the approximate search speed is promptly approximated according to the entire search movement amount calculated based on the permissible circle of confusion, the second ratio with respect to the depth of focus greater than the first ratio, and the aperture value. The focal position is obtained, and the focus adjustment lens is finely driven from the approximate focal position according to the focal distance calculated again based on the permissible circle of confusion and the first ratio to the focal depth. The in-focus direction can be determined accurately and in a short period of time. After that, when the evaluation value is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or less than the predetermined value, the evaluation is performed. It is possible to realize a focus direction determination method the position of the focus adjustment lens when the value is obtained may perform final positioning as an accurate focus position.

  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.

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

  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, in the video camera 1 with an autofocus function, the interchangeable AF lens unit 3 is chucked with respect to the camera body unit 2 (not shown). ), A communication path 30 is formed between the camera body 2 and the interchangeable AF lens unit 3 via the electrical connection point 29.

  The camera body 2 controls the focus adjustment by the solid-state imaging device 26, the signal processing unit 27 that performs predetermined signal processing on the imaging signal obtained by the solid-state imaging device 26, and the interchangeable AF lens unit 3. A portion 28 is provided.

  On the other hand, the interchangeable AF lens unit 3 drives the focus adjustment lens 21 in the direction of the arrow h1 or h2 via the actuator 23 by the focus controller 25 under the control of the control unit 28, or the diaphragm 22 via the motor 24. The open / close state of the is controlled.

(3) Focus Adjustment Processing Procedure In the video camera 1 with an autofocus function, as shown in FIG. 4, the routine RT1 is entered from the start step, and the process proceeds to the next subroutine SRT1. The in-focus direction is recognized by driving with.

  At this time, in the video camera 1 with an autofocus function, when the focus adjustment lens 21 is far from the focus position and the focus direction cannot be recognized at all, the process proceeds to the next subroutine SRT2 for focus adjustment. An overall search is made as to where the approximate in-focus position exists within the movable range in which the lens 21 can move, and the process proceeds to the next subroutine SRT3.

  Incidentally, the video camera 1 with an autofocus function is adapted to directly shift to the subroutine SRT4 and finally search for the in-focus position when the in-focus direction can be recognized in the subroutine SRT1.

  In the subroutine SRT3, the video camera 1 with an autofocus function searches for an approximate in-focus position by an overall search, and then recognizes the in-focus direction by finely driving the focus adjustment lens 21 again, and proceeds to the next subroutine SRT4. .

  In the subroutine SRT4, the video camera 1 with an autofocus function finally searches for the in-focus position, and by positioning the focus adjustment lens 21 at the in-focus position, the subject is focused so that there is no slight defocus. The focus adjustment processing procedure is finished.

  Thus, in the video camera 1 with an autofocus function, the focus adjustment processing procedure can be roughly divided into subroutines SRT1 to SRT4. Each of the subroutines SRT1 to SRT4 will be described below.

(4) Microlens Drive The microlens drive, that is, wobbling in the subroutine SRT1, will be described with reference to FIG. In the camera body 2, first, an arbitrary confusion circle diameter d and an arbitrary depth of focus 2Δx formed on the imaging surface of the solid-state imaging device 26 via the focus adjustment lens 21 and the diaphragm 22 of the interchangeable AF lens unit 3. The ratio a is sent to the focus controller 25 of the interchangeable AF lens unit 3 via the communication path 30 by the control unit 28.

  Here, the permissible circle of confusion will be briefly described. Generally, light passing through a lens creates a point image on the focal plane. This point image is a circle having a certain diameter and is also called a blurred circle. The smaller the diameter of this blur circle is, the sharper the focus is recognized with the naked eye, and the larger the diameter is, the more blurry state is, and the permissible circle of confusion represents the limit value of the blur circle that is not perceived by humans. The diameter is the allowable circle of confusion circle d. The permissible circle of confusion d is also a value that is uniquely determined by the resolution of the optical system and the solid-state image sensor 26.

  On the other hand, the depth of focus will be briefly described. When focusing on a certain distance, objects before and after the focused subject are clearly visible to the extent that they can be used practically, and the focus range on the subject side is the depth of field, while There is also a range where the image is clearly imaged at the front and rear at equal intervals on the side, which is the depth of focus 2Δx.

  When the sum of the defocus amounts on the front side and the rear side when the blur of the perception limit occurs is 2Δx, the defocus amount Δx is the allowable confusion circle diameter d and the aperture value of the aperture 22 if the lens aberration is ignored. Based on FNO,

Can be calculated as

  Accordingly, the focus controller 25 calculates the following equation based on the allowable confusion circle diameter d and the ratio a to the focal depth 2Δx supplied from the control unit 28 of the camera body 2 and the aperture value FNO of the aperture 22.

The focus movement amount Δx ′ shown in FIG. 4 is calculated, and the actuator 23 is minutely driven by the actuator 23 by the focus movement amount Δx ′.

  Incidentally, the ratio a with respect to the focal depth 2Δx is a value arbitrarily determined within the range of 0 <a <1, and this indicates that the focal shift amount Δx ′ exceeds the defocus amount Δx, resulting in out of focus. It is designed to prevent the photographer from recognizing it.

  By the way, the meaning of wobbling is to determine whether the focus is in focus or not by moving the focus adjustment lens 21 back and forth from the current position of the focus adjustment lens 21 and detecting the change in the imaging signal obtained as a result. This is because it cannot be judged without it.

  As a result, the signal processing unit 27 of the camera body 2 forms the subject image captured by the focus adjustment lens 21 and the diaphragm 22 provided in the interchangeable AF lens unit 3 on the solid-state image sensor 26, The AF detection unit 27A extracts a high frequency component of the image pickup signal from the image pickup signal obtained as a result, and sends the extraction result to the control unit 28.

  The control unit 28 extracts a high-frequency component level of an imaging signal obtained at a 1/60 second period corresponding to a field period from the solid-state imaging device 26 as an evaluation value on the premise of a TTL (Through the Lens) mountain climbing method, 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 28 finally moves the focus adjustment lens 21 to the predetermined position based on the recognition result of the direction h1 or h2 from which the current position of the focus adjustment lens 21 is moved. The in-focus state is obtained by driving at a feeding speed.

  When the flow of these series of processes is shown in the sequence chart of FIG. 6, in step SP1, the camera body 2 first sets an arbitrary ratio a to the focal depth 2Δx and the allowable confusion circle diameter d to the focus controller of the interchangeable AF lens unit 3. Then, the process proceeds to the next step SP2, and the process is terminated.

  On the other hand, in step SP11, the interchangeable AF lens unit 3 determines the arbitrary ratio a and the allowable circle of confusion diameter d with respect to the focal depth 2Δx supplied from the camera body unit 2, and the aperture of the diaphragm 22 included in the interchangeable AF lens unit 3. Based on the value FNO, the focal point movement amount Δx ′ is calculated according to the equation (2), and the process proceeds to the next step SP12.

  In step SP12, the interchangeable AF lens unit 3 calculates an actual drive amount L1 in consideration of the drive gain of the actuator 23 that drives the actual focus adjustment lens 21 and the gain of the optical system based on the focal shift amount Δx ′. Then, the process proceeds to the next step SP13.

  In step SP13, the interchangeable AF lens unit 3 generates a pulse corresponding to the drive amount L1 and applies it to the actuator 23 every 1/60 seconds corresponding to the field period, thereby moving the focus adjustment lens 21 in the h1 or h2 direction. The wobbling is performed, the process proceeds to the next step SP14, and the process is terminated.

  At this time, the interchangeable AF lens unit 3 wobbles the focus adjustment lens 21 in the h1 or h2 direction every 1/60 seconds, and the subject image captured through the focus adjustment lens 21 and the aperture 22 at that time is captured by the camera. An image is formed on the imaging surface of the solid-state imaging device 26 of the main body 2.

  The control unit 28 of the camera body 2 compares the level of the high-frequency component of the imaging signal sequentially obtained from the solid-state imaging device 26 every 1/60 seconds, and increases the level of the high-frequency component of the imaging signal in the h1 or h2 direction. Can be recognized as the in-focus direction.

  At this time, the interchangeable AF lens unit 3 does not wobble the focus adjustment lens 21 in the direction h1 or h2 once every 1/60 seconds, but instead moves the focus adjustment lens 21 every 1/60 seconds. In addition, by wobbling in the h1 or h2 direction many times, the accuracy of the recognition result of the in-focus direction performed by the control unit 28 of the camera body 2 can be further improved.

(5) Overall Search for In-Focus Position By the way, the video camera 1 with an auto-focus function focuses on the vicinity of the current position of the focus adjustment lens 21 when the in-focus direction cannot be recognized by the micro lens driving of the subroutine SRT1 described above. It is determined that the focal position does not exist, and an approximate in-focus position search (hereinafter referred to as an overall search) is performed from within the movable range of the focus adjustment lens 21 in the subroutine SRT2.

  The control unit 28 of the video camera 1 with an autofocus function is also configured to perform an overall search on the premise of the TTL mountain climbing method, and the focus adjustment lens 21 is moved from the end point in the h2 direction (FIG. 3) of the movable range to the h1 direction. The high-frequency component levels (evaluation values v) of the imaging signals sequentially acquired from the solid-state imaging device 26 at 1/60 second periods corresponding to the field period are extracted and compared, and the evaluation values v It is determined that the position of the focus adjustment lens 21 showing the maximum value at which the level becomes the highest in-focus position.

  Here, the video camera 1 with an autofocus function detects the in-focus position in the shortest possible time by increasing the moving speed of the focus adjustment lens 21 during the entire search, and sets the response time of the autofocus function. It needs to be shortened.

  However, in the video camera 1 with an autofocus function, since the imaging interval is fixed every 1/60 seconds corresponding to the field period, for example, as shown in FIG. 10B, the focus adjustment lens 21 is moved. When the movement speed at the time is increased, the movement amount of the focus adjustment lens 21 from the acquisition of one imaging signal to the acquisition of the next imaging signal, that is, the entire search movement amount ΔX ′ increases, and the evaluation value There is a possibility of overlooking the maximum value of v.

  Therefore, the video camera 1 with an autofocus function adjusts the moving speed of the focus adjustment lens 21 by setting the entire search movement amount ΔX ′ to an optimum value, and performs the entire search in as short a time as possible to maximize the evaluation value v. It is necessary to reliably detect the approximate focal position without overlooking the value.

  By the way, as shown in FIGS. 10A and 10B, the evaluation values v1 to v4 and the evaluation values v11 to v16 acquired by the video camera 1 with an autofocus function at an imaging interval fixed to 1/60 seconds are as follows. The values are different depending on whether the depth of focus is deep or shallow.

  For this reason, the video camera 1 with an autofocus function, for example, as shown in FIG. 10A, when the depth of focus is relatively deep, the focus adjustment lens 21 at a moving speed that does not overlook the maximum value of the evaluation value v. However, when the depth of focus is relatively shallow as shown in FIG. 10B, the change in the characteristic curves of the evaluation values v11 to v16 is steep. If the focus adjustment lens 21 is moved at a movement speed based on the entire search movement amount ΔX ′, there is a possibility that the maximum value is overlooked only by the evaluation values v11 to v16.

  Here, in the video camera 1 with an autofocus function, when the depth of focus is relatively shallow as described above, if the total search movement amount ΔX ′ is reduced as shown in FIG. The moving speed can be reduced, and in this case, although it takes a long time to search, it can be detected without overlooking the evaluation value v31 in the vicinity of the maximum value.

  In other words, the video camera 1 with an autofocus function only needs to adjust the overall search movement amount ΔX ′ in proportion to the focal depth, and therefore the following formula using an arbitrary ratio b to the focal depth is used here.

Accordingly, the total search movement amount ΔX ′ can be calculated as the product of the defocus amount Δx and the ratio b which is ½ of the focal depth (2Δx).

  By the way, in the video camera 1 with an autofocus function, the distance between the defocus amount Δx, which is ½ of the depth of focus (2Δx), the permissible circle of confusion d (FIG. 5), and the aperture value FNO of the aperture 22. The above-described relationship of the expression (1) is established.

  Here, by applying the relationship of the equation (1) to the above-described equation (3), the total search movement amount ΔX ′ is expressed by the following equation:

Can be expressed as

  By the way, in the video camera 1 with an autofocus function, since the allowable circle of confusion diameter d is a fixed value, the total search movement amount ΔX ′ is proportional to the value of the ratio b and the aperture value FNO of the aperture 22. Become.

  Here, the ratio b is a value arbitrarily determined within the range of 0 <b. However, if the ratio b is relatively large, the overall search movement amount ΔX ′ also increases, and therefore the time required for the overall search is shortened. However, since the imaging interval is 1/60 second, there is a high possibility that the evaluation value v31 near the maximum value is overlooked.

  On the other hand, when the ratio b is relatively small, the total search movement amount ΔX ′ is small, so that the time required for the total search becomes long, but the possibility of overlooking the evaluation value v31 in the vicinity of the maximum value can be kept low. .

  The overall search movement amount ΔX ′ changes in proportion to the change of the aperture value FNO of the aperture 22 even if the value of the ratio b is fixed, as is apparent from the equation (4).

  For this reason, the video camera 1 with an autofocus function is configured so that even if the aperture value FNO of the aperture 22 is set to an arbitrary value within the maximum / minimum range, the entire search can be performed reliably and in a short time. b is set to an optimum value.

  Incidentally, the video camera 1 with an autofocus function sets the ratio b to a value (for example, b = 20) larger than the ratio a (0 <a <1) in the minute lens driving described above as (b). The total search movement amount ΔX ′ obtained according to the equation (4) can be set to a value larger than the focal movement amount Δx ′ obtained according to the equation (2).

  Therefore, the control unit 28 (FIG. 3) of the camera body 2 replaces the allowable confusion circle diameter d and the ratio b (for example, b = 20) with respect to the depth of focus, and calculates an overall search movement amount ΔX ′. 3 to the focus controller 25.

  The focus controller 25 is based on the permissible circle of confusion diameter d and the ratio b to the depth of focus supplied from the control unit 28 of the camera body 2 and the aperture value FNO of the aperture 22 according to the equation (4). ΔX ′ is calculated, and the focus adjustment lens 21 is moved by the actuator 23 by the entire search movement amount ΔX ′.

  Subsequently, the signal processing unit 27 of the camera body unit 2 forms an object image captured by the focus adjustment lens 21 and the diaphragm 22 provided in the interchangeable AF lens unit 3 on the solid-state imaging device 26, and The AF detection unit 27A extracts the evaluation value v (the level of the high frequency component of the imaging signal) for the imaging signal obtained at each result imaging interval (1/60 second), and sends the extraction result to the control unit 28.

  Then, the control unit 28 determines whether or not the in-focus position is near the current position of the focus adjustment lens 21 using the obtained evaluation value v. If there is no in-focus position near the current position, Until the maximum value of the evaluation value v is detected, the permissible circle of confusion diameter d and the ratio b to the depth of focus are repeatedly sent to the focus controller 25 of the interchangeable AF lens unit 3 every imaging interval (1/60 seconds). When the evaluation value v in the vicinity of the maximum value is detected, it is determined that the approximate focus position has been detected, and the entire search is terminated.

  For example, in FIG. 10C, the video camera 1 with an autofocus function evaluates the evaluation value while moving the focus adjustment lens 21 sequentially from the position x21 closest to the h2 side to the h1 side at every imaging interval (1/60 seconds). v21, v22,... are acquired.

  Then, the video camera 1 with the autofocus function moves the focus adjustment lens 21 to the position x31 and obtains the evaluation value v31. The two consecutive evaluation values v30 and v31 are both greater than or equal to a predetermined threshold value vt, and Since the difference value vd31 is equal to or less than the predetermined value, it is determined that the evaluation value v31 is a value near the maximum value of the evaluation value v, and the position x31 from which the evaluation value v31 is acquired is an approximate focus position. Determine.

  When this series of processing is shown in the sequence chart of FIG. 7, in step SP31, the camera body 2 sets the allowable confusion circle diameter d and an arbitrary ratio b to the focal depth to the focus controller 25 of the replacement AF lens 3 through the communication path 30. Then, the process proceeds to the next step SP32 and the process is terminated.

  On the other hand, in step SP41, the replacement AF lens 3 determines an arbitrary ratio b and allowable confusion circle diameter d with respect to the focal depth supplied from the camera body 2 and the aperture value FNO of the aperture 22 included in the replacement AF lens 3. Based on the above, the total search movement amount ΔX ′ is calculated according to the equation (4), and the process proceeds to the next step SP42.

  In step SP42, the replacement AF lens 3 calculates an actual drive amount L2 in consideration of the drive gain of the actuator 23 that drives the actual focus adjustment lens 21 and the gain of the optical system based on the total search movement amount ΔX ′. Then, the process proceeds to the next step SP43.

  In step SP43, the replacement AF lens 3 drives the focus adjustment lens 21 by generating a pulse corresponding to the drive amount L2 and applying it to the actuator 23 every 1/60 seconds corresponding to the field period to drive the drive amount L2. And move to the next step SP44 to end the process.

  Then, the replacement AF lens 3 moves the focus adjustment lens 21 by the drive amount L2 every 1/60 seconds, and captures the subject image captured through the focus adjustment lens 21 and the aperture 22 in the camera body 2. The image is formed on the imaging surface of the solid-state imaging device 26.

  The control unit 28 of the camera body unit 2 sequentially moves the focus adjustment lens 21 from the end point on the h2 side of the movable range, while the high frequency component of the imaging signal sequentially obtained from the solid-state imaging device 26 every 1/60 seconds. Each level (that is, evaluation value v) is compared, and the position of the focus adjustment lens 21 where two consecutive evaluation values v are both equal to or greater than a predetermined threshold value vt and the difference value is equal to or less than a predetermined value is approximately It is determined that it is the in-focus position.

  As a result, when the optimally set ratio b (for example, b = 20) is used, the video camera with an autofocus function 1 has a large aperture value FNO of the aperture 22 and a deep depth of focus (FIG. 10A). By setting the overall search movement amount ΔX ′ to a relatively large value according to the equation (4), the moving speed of the focus adjustment lens 21 is increased, and a relatively small imaging interval fixed at 1/60 seconds (ie, The approximate focal point position x4 can be detected in a relatively short time).

  Further, in the video camera 1 with an autofocus function, even when the same ratio b (b = 20) is used, when the aperture value FNO of the aperture 22 is small and the depth of focus is shallow (FIG. 10C), equation (4) Accordingly, by setting the overall search movement amount ΔX ′ to a relatively small value, the movement speed of the focus adjustment lens 21 is slowed down and a relatively large imaging interval (that is, a relatively long time) fixed at 1/60 seconds. Thus, the approximate in-focus position x31 can be reliably detected.

(6) Micro lens driving again The video camera 1 with an autofocus function detects the approximate in-focus position by the overall search of the subroutine SRT2, and then executes the micro lens driving of the subroutine SRT1 again in the subroutine SRT3. Determine the in-focus direction.

(7) In-focus position search When the video camera 1 with the autofocus function recognizes the in-focus direction from the current position of the focus adjustment lens 21 by the above-described minute lens drive, the focus camera searches for the focus according to the in-focus position search subroutine SRT4. The adjustment lens 21 is accurately moved to the in-focus position.

  In the in-focus position search subroutine SRT4, similarly to the above-described in-focus position overall search subroutine SRT2, the process according to the sequence chart of FIG. 7 is performed. It is set to a value (for example, b = 2) smaller than the value of the ratio b (b = 20) in the overall search for the focal position.

  Therefore, the overall search movement amount ΔX ′ calculated by the focus controller 25 according to the above-described equation (4) is smaller than that in the above-described overall search for the in-focus position, that is, when the focus adjustment lens 21 is driven. The moving speed is also reduced.

  For example, in the case of FIG. 10C, the control unit 28 of the camera body 2 determines that the approximate in-focus position is the position x31 by the above-described in-focus position overall search subroutine SRT2, and further, the minute lens drive subroutine SRT3. It is recognized that the in-focus direction is on the h2 side from the position x31.

  Next, the focus controller 25 of the interchangeable lens unit 3 enlarges the vicinity of the maximum value of the evaluation value v in FIG. 10C, and as shown in FIG. 8, the allowable confusion circle diameter d and the focal depth acquired from the control unit 28. The overall search movement amount ΔX ′ is calculated based on the value of the ratio b to (b = 2), and the entire search movement amount of the focus adjustment lens 21 is more than the position x31 during 1/60 seconds that is the imaging interval. The position is moved to the position x41 on the h2 side by ΔX ′.

  At this time, the control unit 28 calculates a difference value vd41 between the evaluation value v41 acquired at the current position x41 of the focus adjustment lens 21 and the previous evaluation value v31, and the evaluation value v41 and the previous evaluation value v31 are obtained. It is sequentially determined whether or not both are equal to or greater than a predetermined threshold value vt and the difference value vd41 is equal to or less than a predetermined value.

  In this case, although both the evaluation value v41 and the immediately preceding evaluation value v31 are equal to or greater than the predetermined threshold value vt, the difference value vd41 is not equal to or less than the predetermined value, so the control unit 28 determines the current position (x41) of the focus adjustment lens 21. Is determined not to be the in-focus position.

  Thereafter, the control unit 28 repeats the above-described series of processing every 1/60 seconds that is the imaging interval, so that the permissible circle of confusion diameter d and the ratio b (b = 2) to the focal depth sent from the control unit 28 are obtained. Based on this, the focus controller 25 sequentially moves the focus adjustment lens 21 from the position x41 to the position x44.

  Then, when the focus adjustment lens 21 is moved to the position x44, the control unit 28 determines that the current evaluation value v44 acquired from the AF detection unit 27A of the signal processing unit 27 and the previous evaluation value v43 are both predetermined threshold values. Since the difference value vd44 is equal to or greater than vt and the difference value vd44 is equal to or less than a predetermined value, it is determined that the current position x44 from which the evaluation value v44 is acquired is the in-focus position, and the final in-focus position search is terminated.

  As described above, the video camera 1 with an autofocus function can search for the in-focus position by moving the focus adjustment lens 21 little by little every 1/60 seconds that is the imaging interval by the focus controller 25. Finally, the focus adjustment lens 21 can be accurately moved to the in-focus position, and as a result, the subject can be accurately focused.

(8) Operation and Effect In the above configuration, the video camera 1 with an autofocus function adjusts the focus even when the interchangeable AF lens unit 3 having any lens characteristics is mounted on the camera body unit 2. The interchangeable AF lens unit 3 via the communication path 30 by the control unit 28 with an arbitrary ratio a to the allowable confusion circle diameter d and the focal depth 2Δx formed on the imaging surface of the solid-state imaging device 26 via the lens 21 and the diaphragm 22. The focus movement amount Δx ′ for discriminating the in-focus direction by wobbling the focus adjustment lens 21 within a range in which the cameraman cannot recognize the focus shift is sent to the interchangeable AF lens unit 3. The focus controller 25 can be calculated.

  Then, the focus controller 25 of the interchangeable AF lens unit 3 calculates the focus movement amount Δx ′ according to the above-described equation (2), and finely drives the focus adjustment lens within a range in which the cameraman cannot recognize the focus shift, and the in-focus direction Since the driving amount L1 of the actuator for discriminating can be calculated based on the focal movement amount Δx ′, the focus adjustment lens 21 can be wobbled according to the driving amount L1.

  From the viewpoint of the camera body 2, this means that an arbitrary ratio a to the permissible circle of confusion d and the depth of focus 2Δx is set regardless of the lens characteristics of the interchangeable AF lens 3 mounted. By simply sending it to the focus controller 25 of the interchangeable AF lens unit 3, the focus adjustment lens 21 can be wobbled to determine the in-focus direction, further improving the versatility of the video camera 1 with an autofocus function. Can be made.

  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. Since the focus movement amount Δx ′ for wobbling can be calculated on the third side and the in-focus direction can be determined, the autofocus function can function properly regardless of the type of the replaceable AF lens unit to be mounted. it can.

(9) Other Embodiments In the above-described embodiment, the case where the interchangeable AF lens unit 3 has the diaphragm 22 as shown in FIG. 3 has been described. However, the diaphragm 22 may be provided in the camera body 2 as shown in FIG.

  In this case, the control unit 28 of the camera body 2 sends the aperture value FNO of the aperture 22 to the focus controller 25 of the interchangeable AF lens unit 3 via the communication path 30 in addition to the allowable confusion circle diameter d and the ratio a to the focal depth 2Δx. In the interchangeable AF lens unit 3, the focus movement amount Δx ′ is calculated according to the equation (2) by the focus controller 25, calculated based on the focus movement amount Δx ′, and used for focus adjustment according to the drive amount L 1. The lens 21 can be wobbled.

  In the above-described embodiment, an arbitrary ratio a to the allowable confusion circle diameter d and the focal depth 2Δx is sent from the control unit 28 to the focus controller 25 of the interchangeable AF lens unit 3 via the electrical connection point 29 and the communication path 30. However, the present invention is not limited to this, and is transmitted to the focus controller 25 of the interchangeable AF lens unit 3 by a wireless communication method such as Bluetooth communication method or IEEE (Institute of Electrical and Electronics Engineers) 802.11g. You may make it do.

  Furthermore, in the above-described embodiment, the in-focus direction is determined by using the level of the high-frequency component of the imaging signal acquired from the solid-state imaging device 26 at a 1/60 second period corresponding to the field period as an evaluation value. Although the present invention is not limited to this, the in-focus direction is determined by using the level of the high-frequency component of the imaging signal acquired at a 1/30 second period corresponding to the frame period as an evaluation value. Also good.

  Further, in the above-described embodiment, the interchangeable lens unit of the video camera is configured by the actuator 23 as the drive unit, the focus controller 25 as the drive amount calculation unit, and the aperture 22 as the aperture, and serves as the control unit. The case where the camera body is configured by the control unit 28 has been described. However, the present invention is not limited to this, and the interchangeable lens of the video camera is not limited to this, and includes a driving unit having various circuit configurations, a driving amount calculation unit, and a diaphragm. The camera body of the video camera may be configured by a control unit having various circuit configurations.

  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 structure of the 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 an approximate line figure used for explanation of a focal depth. It is a basic diagram which shows the micro drive control processing sequence of the lens for focus adjustment. It is a basic diagram which shows the whole search process sequence of a focal point position. It is a basic diagram with which it uses for description of the mode of a focus position search. It is a basic diagram which shows the circuit structure of the video camera with an autofocus function in other embodiment. 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 ... Focus adjustment lens, 22 ... Aperture, 23 ... Actuator, 25 ... Focus controller, 27... Signal processing unit, 28... Control unit, 30.

Claims (4)

A video camera comprising a camera body and an interchangeable lens part detachably attached to the camera body,
The interchangeable lens unit includes a drive unit that drives a focus adjustment lens, a drive amount calculation unit that calculates a drive amount of the focus adjustment lens, and a diaphragm.
In the camera body, an allowable confusion on the imaging surface is obtained in order to obtain a focal shift amount for recognizing the in-focus direction on the imaging surface of the imaging means by minutely driving the focus adjustment lens via the driving means. When the circle diameter and the first ratio with respect to the depth of focus are supplied to the drive amount calculation unit of the interchangeable lens unit, and the focus adjustment lens is finely driven by the drive unit according to the focus movement amount However, when the in-focus direction cannot be recognized, the allowable confusion circle diameter is calculated in order to obtain an overall search movement amount for searching for an approximate in-focus position by sequentially moving the focus adjustment lens within the movable range. When the control hand to supply a second ratio with respect to the focal depth made with greater than said first ratio to said driving amount calculation means of the interchangeable lens unit The equipped,
The drive amount calculation means of the interchangeable lens unit is configured to adjust the focus adjustment lens based on the permissible circle of confusion and the first ratio to the depth of focus supplied from the control means, and the aperture value of the stop. the calculated focus movement amount, or the second ratio with respect to the circle of confusion diameter and the depth of focus is supplied from the control unit, the whole of the aperture of the aperture value and the focus adjusting lens on the basis of the calculating a search movement amount, the drive means, is minutely drives the focus adjustment lens according to the focus movement amount for recognizing the focus direction, or for the focus adjustment in response to the overall search movement amount Move the lens,
The control means of the camera main body obtains the approximate in-focus position based on an evaluation value for the image pickup signal obtained from the image pickup means via the focus adjustment lens at that time, and then the allowable confusion. The circle diameter and the first ratio with respect to the depth of focus are supplied again to the drive amount calculation means, and the focus adjustment lens is moved to the approximate focus by the drive means according to the focus movement amount obtained as a result. When the final focus direction is determined by minute driving from the position, and the evaluation value is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or less than the predetermined value, the evaluation value is The final positioning is performed with the position of the focus adjustment lens when obtained as an accurate in-focus position.
Video camera. The control means provided in the camera body, for recognizing the in-focus direction in the imaging plane of the imaging means the camera main body and detachably provided with interchangeable lens unit for focus adjustment lens by minute movement A first data supply step for supplying a permissible circle of confusion on the imaging surface and a first ratio with respect to the depth of focus from the control unit to the drive amount calculation unit of the interchangeable lens unit in order to obtain a focal movement amount ; ,
By the driving amount calculation means, a first ratio of the allowable circle of confusion and the depth of focus is supplied from said control means, of the focus adjustment lens on the basis of the aperture of the aperture in the interchangeable lens unit calculating the focus shift amount, and the minute driving control step of finely driving the focusing lens in accordance with the focal shift amount for recognizing the coupling Asekata direction,
When the in-focus direction cannot be recognized by the minute drive control step, an approximate in-focus position is searched by sequentially moving the focus adjustment lens within the movable range via the driving means of the camera body. In order to obtain the total search movement amount for the above-mentioned, the permissible circle of confusion and the second ratio with respect to the depth of focus, which is larger than the first ratio, are used to drive the interchangeable lens unit from the control means. A second data supply step for supplying to the quantity calculation means;
The drive amount calculation means calculates the overall search movement amount of the focus adjustment lens based on the allowable circle of confusion, the second ratio with respect to the depth of focus, and the aperture value of the aperture. An in-focus position acquisition step of obtaining the approximate in-focus position by moving the focus adjustment lens by the driving means in accordance with a search movement amount;
Based on the permissible circle of confusion supplied again from the control means, the first ratio with respect to the depth of focus, and the aperture value, the focus movement amount of the focus adjustment lens is calculated, and the focus movement is calculated. An in-focus direction determining step of determining the final in-focus direction by minutely driving the focus adjustment lens from the approximate in-focus position according to the amount;
The evaluation is performed when the evaluation value for the imaging signal obtained from the imaging means through the focus adjustment lens at that time is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or less than the predetermined value. A focusing direction determination method including a positioning step of performing final positioning using the position of the focus adjustment lens when the value is obtained as an accurate focusing position . A video camera comprising a camera body and an interchangeable lens part detachably attached to the camera body,
The interchangeable lens unit includes a driving unit that drives a focus adjustment lens, and a driving amount calculation unit that calculates a driving amount of the focus adjustment lens.
In the camera body, an allowable confusion on the imaging surface is obtained in order to obtain a focal shift amount for recognizing the in-focus direction on the imaging surface of the imaging means by minutely driving the focus adjustment lens via the driving means. and the circle diameter, and the first ratio with respect to the focal depth, and a diaphragm aperture value supplied to the driving amount calculation means of the interchangeable lens unit, the focus adjustment lens by said driving means in accordance with the focal shift amount If the focus direction cannot be recognized even when the lens is driven minutely, the entire search movement amount for searching the approximate focus position is obtained by sequentially moving the focus adjustment lens within the movable range. The permissible circle of confusion, the second ratio with respect to the depth of focus, which is a value larger than the first ratio, and the aperture value are set to Comprising a control means for supplying to the momentum calculating means,
The drive amount calculation unit of the interchangeable lens unit is configured to adjust the focus based on the permissible circle of confusion supplied from the control unit, the first ratio to the depth of focus, and the aperture value of the aperture. The focus movement amount of the focus adjustment lens is calculated based on the allowable confusion circle diameter supplied from the control means, the second ratio to the focal depth, and the aperture value of the aperture. The total search movement amount is calculated, and the driving means finely drives the focus adjustment lens according to the focus movement amount in order to recognize the focus direction , or the focus according to the total search movement amount. Move the adjustment lens,
The control means of the camera main body obtains the approximate in-focus position based on an evaluation value for the image pickup signal obtained from the image pickup means via the focus adjustment lens at that time, and then the allowable confusion. The circle diameter, the first ratio to the depth of focus, and the aperture value of the aperture are supplied again to the drive amount calculation means, and the focus adjustment amount is adjusted by the drive means according to the focus movement amount obtained as a result. The final focusing direction is determined by minutely driving the lens from the approximate focus position, and the evaluation value is equal to or greater than a predetermined threshold value and the difference from the previous evaluation value is equal to or less than the predetermined value. In this case, final positioning is performed by using the position of the focus adjustment lens when the evaluation value is obtained as an accurate in-focus position.
Video camera. The control means provided in the camera body, for recognizing the in-focus direction in the imaging plane of the imaging means the camera main body and detachably provided with interchangeable lens unit for focus adjustment lens by minute movement In order to obtain the amount of focus movement, the permissible circle of confusion on the imaging surface, the first ratio with respect to the depth of focus, and the aperture value of the stop are supplied from the control unit to the drive amount calculation means of the interchangeable lens unit . 1 data supply step;
Calculated by the driving amount calculation means, and the permissible circle of confusion diameter supplied from the control unit, a first ratio of the depth of focus, the focus movement amount of the focus adjustment lens on the basis of the above aperture and a fine driving control step of finely driving the focusing lens in accordance with the focal shift amount for recognizing the coupling Asekata direction,
When the in-focus direction cannot be recognized by the minute drive control step, an approximate in-focus position is searched by sequentially moving the focus adjustment lens within the movable range via the driving means of the camera body. In order to obtain the total search movement amount for the above, the permissible circle of confusion, the second ratio with respect to the depth of focus, which is a value larger than the first ratio, and the aperture value of the diaphragm are determined from the control means. A second data supply step for supplying to the drive amount calculation means of the interchangeable lens unit;
The drive amount calculation means calculates the overall search movement amount of the focus adjustment lens based on the permissible circle of confusion, the second ratio to the depth of focus, and the aperture value. An in-focus position acquisition step for obtaining the approximate in-focus position by moving the focus adjustment lens by the driving means according to the amount;
Based on the permissible circle of confusion supplied again from the control means, the first ratio with respect to the depth of focus, and the aperture value of the diaphragm, the focus movement amount of the focus adjustment lens is calculated, An in-focus direction determining step of determining the final in-focus direction by minutely driving the focus adjustment lens from the approximate in-focus position according to a focus movement amount;
The evaluation is performed when the evaluation value for the imaging signal obtained from the imaging means through the focus adjustment lens at that time is equal to or greater than a predetermined threshold and the difference from the previous evaluation value is equal to or less than the predetermined value. A focusing direction determination method including a positioning step of performing final positioning using the position of the focus adjustment lens when the value is obtained as an accurate focusing position .

Images