JP2001305419A - Automatic focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of hunting due to an excessive drive at the time of correcting a backlash, in an automatic focusing device used for a still camera and a video camera, etc. SOLUTION: In the case of necessitating reversing a photographic lens in a driving direction at the process of focusing the photographic lens while repeatedly performing a focus detecting operation by a focus detecting means and a photographic lens driving operation by a lens driving/controlling means, a backlash correcting operation for correcting the driving quantity of the photographic lens is performed, and whether or not the photographic lens is excessively driven in accordance with the backlash correcting operation is decided by a backlash correction inhibiting means based on the focus detection results by the focus detecting means obtained before/after the backlash correcting operation is performed by the backlash correcting means, and in the case the photographic lens is excessively driven, the backlash correcting operation by the backlash correcting means is inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device used for a still camera, a video camera and the like.

[0002]

2. Description of the Related Art Conventionally, an automatic focusing apparatus has performed focus detection by detecting the focus of a photographing lens and driving the photographing lens according to the detection result. In such an automatic focusing apparatus, when the driving direction of the photographing lens is reversed, the backlash in the driving system of the photographing lens causes a difference between the driving amount and the actual moving amount of the photographing lens. In this method, the driving amount is stored, and the driving amount at the time of reversing the driving direction is corrected based on the backlash correction amount (hereinafter, such correction of the driving amount is simply referred to as “backlash correction”). Call).

FIG. 10 is a diagram for explaining backlash correction. In FIG. 10, L1 indicates a photographing lens,
M1 indicates a lens supporting member, and M2 indicates a lens driving member. The lens driving member M2 is provided with an actuator (not shown) and an encoder for monitoring the moving amount of the photographing lens L1, and the driving control of the photographing lens L1 is based on the result of monitoring the moving amount of the photographing lens L1 by the encoder. It is realized by controlling the actuator based on

Hereinafter, the backlash correction will be described with reference to FIG. 10. In the following description, the backlash is moved from the lens position a to the left while the backlash is blocked on the left side, and then the backlash is corrected to the right. An example of backlash correction performed when moving to return to the lens position a will be described. In the following, for the sake of simplicity, the movement amount of the lens driving member M2 is used as the driving amount of the photographing lens L1.

First, the state shown in FIG. 10A (photographing lens L
When the photographing lens L1 is moved leftward by X1 from the state where 1 is located at the lens position a and the play is jammed to the left), backlash correction is not performed and X1 is set as the movement amount of the lens driving member M2. Then, the photographing lens L1 is in the state of FIG. On the other hand, when the photographing lens L1 is moved rightward by X1 from the state of FIG. 10B (the state in which the backlash is jammed to the left), the driving direction is reversed, so that backlash correction is performed and the lens driving member is moved. M
The movement amount of No. 2 is increased by Bk corresponding to the backlash amount to become (X1 + Bk). Therefore, the play is blocked on the movement direction side (right side), and the photographing lens L1 returns to the lens position a (the state of FIG. 10C).

[0006]

However, FIG.
As shown in (C) (corresponding to FIG. 10 (C)), the shooting lens L1 is tilted rightward or downward with some force (for example, the shooting lens L1 is tilted downward or upward) in a state where the play is jammed to the right. In such a case, the taking lens L1 moves rightward by an amount corresponding to Bk as shown in FIG. 11C-1. That is, FIG.
The state of 1) corresponds to the fact that the photographing lens L1, which should be returned to the lens position a from the state of FIG. 10B, is excessively driven by the backlash correction and overrun.

For this reason, in the state shown in FIG.
Driving control for moving the taking lens L1 to the left by Bk and returning to the lens position a is required. However, in such drive control, since the drive direction is reversed, backlash correction is performed, and the movement amount of the lens drive member M2 becomes
It is increased by Bk corresponding to the amount of backlash (B
k + Bk). Therefore, the taking lens L
1 does not return to the lens position a but overruns again
1 (C-2). That is, the photographing lens L1
Means that hunting is repeated by moving left and right near the lens position a due to overrun at the time of backlash correction.

[0008] The backlash correction amount used in the backlash correction varies depending on individual differences even in a photographic lens having the same structure, but the actual measured value of the backlash correction amount for each photographic lens is stored. That leads to an increase in cost. Therefore, in a general automatic focusing device, a standard backlash correction amount is often stored.

Therefore, in the automatic focusing device in which the standard backlash correction amount is stored, there is a possibility that an overrun occurs due to a mismatch between the actual backlash amount and the backlash correction amount, and hunting occurs. is there. Therefore, an object of the present invention is to provide an automatic focus adjustment device that can avoid occurrence of hunting due to excessive driving at the time of backlash correction.

[0010]

An automatic focus adjusting apparatus according to claim 1, wherein said focus detecting means repeatedly detects the focus of said photographing lens, and said photographing lens according to a focus detection result by said focus detecting means. Driving the lens, and detecting the focus by the focus detecting means and driving the photographing lens by the lens driving control means repeatedly to adjust the focus of the photographing lens. An automatic focus adjustment device comprising: a backlash correction unit for performing a backlash correction for correcting a driving amount of the photographing lens when a reversal of the driving direction of the lens is necessary. Based on the focus detection result by the focus detection unit immediately after the correction, the photographing lens is excessively Determining whether or not a dynamic, when the driving of the photographic lens was excessive, characterized in that a backlash compensation inhibiting means for inhibiting the backlash correction by the backlash compensation means.

According to a second aspect of the present invention, in the automatic focus adjusting apparatus according to the first aspect, the backlash correction prohibiting unit includes the focus detecting unit immediately after the backlash correction by the backlash correcting unit. When it is recognized from the focus detection result that the driving direction of the photographing lens needs to be reversed again, it is determined whether the photographing lens has been excessively driven by the backlash correction. I do.

According to a third aspect of the present invention, in the automatic focus adjusting apparatus according to the second aspect, the backlash correction prohibiting unit is configured to detect the focus immediately after the backlash correction by the backlash correcting unit. If the reversal of the driving direction of the photographing lens is necessary again according to the focus detection result by the means, and it is recognized that the defocus amount exceeds a predetermined amount, the photographing lens is excessively driven by the backlash correction. It is characterized in that it is determined that

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. In each of the embodiments described below, a description will be given using a still camera having the function of the automatic focusing device of the present invention. FIG. 1 is a functional block diagram of such a still camera.

In FIG. 1, an interchangeable lens 11 is mounted on a camera body 10 by a mounting mechanism (not shown). In the camera body 10, a main mirror 13 and a sub-mirror 14 are arranged on the optical axis of a photographing lens 12 in the interchangeable lens 11, and an AF module 15 is arranged in a reflection direction of the sub-mirror 14. The AF module 15 has a re-imaging optical system (not shown) and an AF sensor, and is connected to a sensor drive circuit 16.

The camera body 10 includes a CPU 17,
Lens drive control circuit 18, motor 19, encoder 20
And an operation unit 21 (including a release). CPU
17 is a sensor drive circuit 16, a lens drive control circuit 18
Connected to an operation unit 21 via a switch unit (not shown).
Is connected to the lens information storage circuit 22 in the inside. The switch unit is provided with a switch that turns on when the release is half-pressed (hereinafter, referred to as a “half-press switch”).

The motor 19 is connected to a lens drive control circuit 18 and an encoder 20.
It is connected to the PU 17 and to the lens moving mechanism 23 in the interchangeable lens 11. Further, the interchangeable lens 11
, The lens moving mechanism 23 is connected to the photographing lens 12. The lens information storage circuit 22 in the interchangeable lens 11 stores a lens driving amount conversion parameter (hereinafter, referred to as an opening F value or a defocus amount) of the photographing lens 12.
A “defocus amount lens drive amount conversion parameter”, a standard backlash correction amount, and the like are stored in advance as lens information.

FIGS. 2 to 7 are operation flowcharts of the present embodiment. Hereinafter, the operation of the present embodiment will be described with reference to FIGS. First, when the main power is turned on, the CPU 17 initializes the contents of variables and flags assigned to the internal memory (S101 in FIG. 2). For example, in the present embodiment, as such initialization processing, a focusing flag (a flag set in a focused state) and a backlash correction permission flag (a flag set when backlash correction is permitted) are set. ), And also clears history data (including a moving object flag (a flag set when the subject is a moving object)) to be described later.

Next, the CPU 17 determines whether or not the half-press switch is turned on (S102 in FIG. 2), and performs the above-described initialization processing until the half-press switch is turned on (S2 in FIG. 2).
(Corresponding to 101). When recognizing that the half-push switch has been turned on by the determination in S102 of FIG. 2, the CPU 17 performs “backlash correction permission determination processing” described later (FIG. S103).

In the course of performing such a process, the light beam incident on the interchangeable lens 11 reaches the main mirror 13 via the photographing lens 12. The light beam that has reached the main mirror 13 is split and guided to the AF module 15 via the sub mirror 14. further,
Such a light flux is guided to an AF sensor (not shown) via a re-imaging optical system (not shown) in the AF module 15.

The CPU 17 controls the accumulation of electric charges in the AF sensor to which the light beam has been guided in this way via the sensor drive circuit 16 (S104 in FIG. 2). That is,
In the sensor drive circuit 16, the AF in the AF module 15
The start and the end of charge accumulation in the sensor are controlled, and the luminous flux guided to the AF sensor is converted into an “electric signal representing a focus state”. Also, the sensor driving circuit 16
Supplies the CPU 17 with the “electric signal representing the state of the focus” obtained by such conversion processing.

In the course of performing such processing,
Based on a feedback pulse from the encoder 20, the CPU 17 averages the position of the photographing lens 12 during a period in which electric charge is accumulated in the AF sensor in the AF module 15 (hereinafter, referred to as “average lens position LPav”). Ask for. Further, the CPU 17 determines the defocus amount and the lens drive amount conversion parameter at the center time (hereinafter referred to as “accumulation center time T [0])” in the center of the period in which electric charge is accumulated by the AF sensor in the AF module 15. LD [0] is read from the lens information storage circuit 22.

As described above, when the “electric signal indicating the focus state” is supplied from the sensor drive circuit 16, the CPU 17 performs A / D conversion on the “electric signal indicating the focus state”.
The conversion is performed (S105 in FIG. 2) and stored in the internal memory. Further, the CPU 17 calculates the defocus amount DF [0] based on the “electrical signal indicating the focus state” stored in the memory after digitization in this way (S10 in FIG. 2).
5). In the present embodiment, for simplicity of description, one focus detection area is used, and one defocus amount is calculated from the area.

After calculating the defocus amount DF [0], the CPU 17 calculates the position of the subject at the accumulation center time T [0] (hereinafter, referred to as "detected subject position P [0]") (S107 in FIG. 2). . For example, based on the average lens position LPav and the defocus amount DF [0], the CPU 17
The detected subject position P [0] is calculated by the following equation.

P [0] = Kdf2p × DF [0] + LPav where Kdf2p is a conversion coefficient of the lens driving amount with respect to the defocus amount, and the defocus amount lens driving amount conversion parameter LD [obtained as described above. 0] and FIG. 2S
This is a value dependent on the defocus amount DF [0] calculated in 106. In the present embodiment, the defocus amount lens movement amount conversion parameter LD [0] at the accumulation center time T [0] is used as the defocus amount lens movement amount conversion parameter at the average lens position LPav.
The defocus amount lens movement amount conversion parameter at the average lens position LPav may be calculated using the defocus amount lens movement amount conversion parameter at the start of accumulation and at the end of accumulation.

By the way, in this embodiment, when the half-push switch is continuously turned on, FIG.
The process of S112 is repeatedly performed. The value calculated in the process of repeating such a process is shown in FIG.
At 11, the data is stored in the memory in the CPU 17 as history data. That is, in the state where the defocus amount DF [0] and the detected object position P [0] are calculated, the previously calculated defocus amount DF [1] and the detected object position P [1] are already recorded as the history data. It will be stored in the memory.

The CPU 107 reads the previous detected subject position P [1] from such history data, and reads the previously read detected subject position P [1] and the newly calculated present detected subject position P [0]. , The current image plane moving speed V
[0] is calculated (S108 in FIG. 2).

Next, the CPU 17 performs a "moving object determination process" described later (S109 in FIG. 2), and then performs a "focus determination process" described later (S110 in FIG. 2). And CPU
17 updates the history data (S111 in FIG. 2). Note that the history data is composed of the accumulation center time, the image plane moving speed, and the moving object flag, in addition to the defocus amount and the detected subject position as described above.

Next, the CPU 17 performs a "lens driving process" to be described later (S112 in FIG. 2), determines again whether or not the half-press switch is turned on (corresponding to S102 in FIG. 2). Are continuously turned on, the processes of S103 to S112 in FIG. 2 are repeatedly performed. Hereinafter, details of the backlash correction permission determination process will be described with reference to FIG.

First, the CPU 17 determines whether or not the backlash correction permission flag is set (S201 in FIG. 3). When the backlash correction permission flag is set, the CPU 17 ends the backlash correction permission determination process because the determination in S202 in FIG. 3 is unnecessary. In this embodiment, once the backlash correction permission flag is set, the half-press switch is turned off to perform initialization processing (S10 in FIG. 2).
1) FIG. 7S606 of “Backlash processing” described later
The set state is maintained until the operation is performed.

On the other hand, when the backlash correction permission flag is cleared, the driving amount of the photographing lens 12 after the half-press switch is turned on (hereinafter referred to as “lens driving amount”) is equal to or more than the backlash correction amount. Is determined (S202 in FIG. 3). When the CPU 17 recognizes that the lens driving amount is smaller than the backlash correction amount by such a determination, the CPU 17 ends the backlash correction permission determination process. On the other hand, when recognizing that the lens driving amount is equal to or larger than the backlash correction amount, the CPU 17 sets a backlash correction permission flag (S203 in FIG. 3).

Since the determination in step S202 in FIG. 3 is performed in a state where the backlash correction permission flag is cleared, the case where the lens drive amount is equal to or more than the backlash correction amount means that the excessive drive due to the backlash correction is performed. This corresponds to the case where the play reduction as required has been completed by the normal lens drive control that does not involve. That is,
In the present embodiment, since the backlash correction permission flag is set when the backlash as needed is completed, excessive driving due to the backlash correction can be suppressed, and hunting can be avoided. is there.

Here, a description will be given of a change in the state of the backlash correction permission flag in the process of repeatedly performing the processing of this embodiment. FIG. 8 is a diagram illustrating an example of a change in the state of the backlash correction permission flag. In FIG.
DF3 indicates the defocus amount detected at the time when the first time of S104 in FIG. 2 is performed, and DF2, DF1, DF0
Indicates a defocus amount detected at the time when S104 in FIG. 2 is performed for the second time and thereafter.

In this embodiment, since the actual calculation of the defocus amount is performed in S106 of FIG. 2 and the drive control of the photographic lens 12 is performed in S112 of FIG. 2, the drive control of the photographic lens 12 based on the defocus amount DF3 is performed. The start of
This is immediately before the defocus amount DF2 is detected. Therefore, the lens drive amount in FIG. 8 (corresponding to the drive amount of the photographing lens 12 after the half-press switch is turned on) does not change until the defocus amount DF2 is detected.

The change in the state of the backlash correction permission flag will be described below with reference to FIG. First, the backlash correction permission flag is cleared by the initialization process of S101 in FIG. 2 when the half-press switch is off. When the half-press switch is switched from off to on at time t0, the first determination in S202 of FIG. 3 is performed until the defocus amount DF3 is detected. But,
At the time when such a determination is made, the backlash correction permission flag is kept cleared since the taking lens 12 is not driven. Immediately before the defocus amount DF2 is detected, the second determination in S202 of FIG. 3 is performed. Since the lens driving amount is less than the backlash correction amount, the backlash correction permission flag is cleared. maintain.

At time t1, the lens drive amount exceeds the backlash correction amount. However, at this point, since the third determination in S202 of FIG. 3 is not performed, the backlash correction permission flag is maintained in a cleared state. The third determination in S202 of FIG. 3 is performed immediately before the defocus amount DF1 is detected (corresponding to time t2). At this point, since the lens driving amount has already exceeded the backlash correction amount, the backlash correction permission flag is set.

Generally, the standard backlash correction amount recorded in the lens information storage circuit 22 in the interchangeable lens 11 often stores the minimum value of the manufacturing tolerance.
Therefore, when the lens drive amount exceeds the backlash correction amount as at time t1, it is unlikely that the driving of the photographing lens 12 corresponding to the actual backlash amount has been completed. Therefore, in order to increase the effect of suppressing hunting, the setting of the backlash correction permission flag is
It is desirable that the shooting is performed in a state where the taking lens 12 is driven to be larger than the backlash correction amount.

In the present embodiment, "determination whether or not the lens drive amount is equal to or more than the backlash correction amount" is not always performed, but is performed in S202 of FIG. Therefore, the time when the lens drive amount exceeds the backlash correction amount (corresponding to time t1) and the time when it is determined whether the lens drive amount is equal to or greater than the backlash correction amount (corresponds to time t2).
There is a time lag between them. That is, in the present embodiment, the backlash correction permission flag is set in a state where the photographing lens 12 is driven to be larger than the backlash correction amount, so that the effect of suppressing hunting is enhanced.

By the way, in FIG. 2S108, the image plane moving speed is calculated using the history data. However, the image plane moving speed calculated using the history data in a state where the play is not completed as required is However, an error from the actual image plane moving speed increases. In the present embodiment, the backlash correction permission flag is set when the backlash correction as required is completed. Therefore, the image plane moving speed is set using the history data in a state where the backlash correction permission flag is set. Is calculated, the image plane moving speed with a small error can be calculated.

Hereinafter, the moving object determination processing will be described in detail with reference to FIG. First, the CPU 17 executes the processing in FIG.
6, it is determined whether or not the focus cannot be detected based on the calculation result of the current defocus amount DF [0] (S301 in FIG. 4). When the CPU 17 recognizes that the focus cannot be detected by such a determination,
The moving object determination processing ends. That is, in the moving object determination processing of the present embodiment, if the focus cannot be detected, the result of the previous moving object determination processing is maintained.

On the other hand, when recognizing that the focus has been detected, the CPU 17 stores the previous image plane moving speed V in the memory.
It is determined whether [1] and the current image plane moving speed V [0] are stored (S302 in FIG. 4). CPU 17
By recognizing that the previous image plane moving speed V [1] and the current image plane moving speed V [0] are stored in the memory by such a determination, the previous image plane moving speed V [1]. Then, it is determined whether or not the current image plane moving speed V [0] is in the same direction (S303 in FIG. 4). On the other hand, when the CPU 17 recognizes that the previous image plane moving speed V [1] and the current image plane moving speed V [0] are not stored in the memory, the CPU 17 clears the moving object flag (S304 in FIG. 4). The determination routine ends.

The CPU 17 determines the previous image plane moving speed V [1] and the current image plane moving speed V
If [0] is recognized to be in the same direction, it is determined whether or not the absolute value of the current image plane moving speed V [0] is equal to or greater than a predetermined value Vth1 (S305 in FIG. 4). On the other hand, the CPU 17
The previous image plane moving speed V [1] and the current image plane moving speed V [0]
When the moving object flag is recognized not to be in the same direction, the moving object flag is cleared (S304 in FIG. 4), and the moving object determination routine ends.

When the CPU 17 recognizes that the current image plane moving speed V [0] is equal to or higher than the predetermined value Vth1 by the determination in S305 in FIG. 4, the previous image plane moving speed V [1] is equal to or higher than the predetermined value Vth2. (S30 in FIG. 4)
6). Note that, in the moving object determination process of the present embodiment, the predetermined value Vt
h1 and Vth2 take values of about 0.75 to 1.5 [mm / s].

On the other hand, if the CPU 17 recognizes that the current image plane moving speed V [0] is less than the predetermined value Vth1, it clears the moving object flag (S304 in FIG. 4) and ends the moving object determination process. When the CPU 17 recognizes that the previous image plane moving speed V [1] is equal to or higher than the predetermined value Vth2 by the determination in S306 in FIG. 4, the CPU 17 sets the moving object flag (S3 in FIG. 4).
08), the moving object determination routine ends. On the other hand, CPU1
7 clears the moving object flag when recognizing that the previous image plane moving speed V [1] is less than the predetermined value Vth2 (FIG. 4S
304), end the moving object determination routine.

As described above, in the moving object determination process of the present embodiment, the two image plane movement speeds are compared with the predetermined values in FIGS. 4S305 and 4306. Therefore, even when one of the image plane moving speeds is erroneously increased to a predetermined value or more due to a variation in focus detection or the like, the moving object flag is not set and the moving object determination can be performed with high accuracy.

The details of the focus determination process will be described below with reference to FIG. First, the CPU 17 executes the processing in FIG.
In step S401, it is determined whether the focus cannot be detected based on the calculation result of the current defocus amount DF [0] in step S6. The determination processing ends. On the other hand, CPU1
7 recognizes that the focus has been detected, and determines whether the absolute value of the current defocus amount DF [0] is less than a predetermined value IFWth (S402 in FIG. 5). Note that the predetermined value IFWth may generally be set to a value of about 50 to 150 [μm].

The CPU 17 makes such a determination,
The absolute value of the current defocus amount DF [0] is a predetermined value IFWth
If it is determined that the distance is less than the predetermined value, the focus flag is set (S403 in FIG. 5), and the focus determination process ends. On the other hand, C
When recognizing that the absolute value of the current defocus amount DF [0] is equal to or greater than the predetermined value IFWth, the PU 17 clears the focus flag (S404 in FIG. 5) and ends the focus determination process.

The details of the lens driving process will be described below with reference to FIG. First, the CPU 17 executes the processing in FIG.
Based on the calculation result of the current defocus amount DF [0] in 06, it is determined whether or not focus detection has been impossible (S501 in FIG. 6). The process ends. That is,
In the moving object determination process of the present embodiment, when it is recognized that the focus cannot be detected, no new lens driving is performed.

On the other hand, when recognizing that the focus has been detected, the CPU 17 determines whether or not the moving object flag is set (S502 in FIG. 6). CPU 17
If it is recognized that the moving object flag is set by such determination, the lens drive target value for the moving subject is updated (S503 in FIG. 6). On the other hand, the CPU 17
When it is recognized that the moving object flag is cleared, the lens drive target value for the still subject is updated (S50 in FIG. 6).
4).

Next, the CPU 17 compares the previous lens driving direction with the lens driving direction indicated by the lens driving target value updated in FIG. 6S503 and FIG. 6S504, and determines whether the driving direction needs to be reversed. A determination is made (S505 in FIG. 6). When the CPU 17 recognizes that the reversal of the driving direction is not required by such a determination,
The lens drive control based on the lens drive target value is started (S506 in FIG. 6). On the other hand, when recognizing that the driving direction needs to be reversed, the CPU 17 performs the following “backlash correction processing” (S507 in FIG. 6), and starts lens driving control based on the lens driving target value (S50 in FIG. 6).
6).

Hereinafter, the backlash correction processing will be described in detail with reference to FIG. First, the CPU 17 determines whether or not the backlash correction permission flag has been cleared (S601 in FIG. 7), and ends the backlash correction processing if the backlash correction permission flag has been cleared. On the other hand, when the backlash correction permission flag is set, the CPU 17 determines whether reversal of the driving direction is necessary again by focus detection immediately after the backlash correction (S602 in FIG. 7).

Note that such a determination can be realized by using, for example, a flag that is set / cleared under the following conditions. Set condition: When backlash correction is performed (corresponding to S603 to S604 in FIG. 7). Clearing conditions: When the drive direction is not required to be reversed (corresponding to NO in S505 in FIG. 6) or when the backlash correction permission flag is cleared (corresponding to S606 in FIG. 7).

The case where the drive direction needs to be reversed again by the focus detection immediately after the backlash correction is defined as the case where the photographing lens 1 is used by the previous backlash correction.
2 may be driven excessively, or fine adjustment of the taking lens 12 may be performed under normal lens drive control without excessive driving. The CPU 17 executes the processing in FIG.
When it is recognized that the backlash correction is not performed immediately before the current focus detection by the determination of 2, the lens drive control for the backlash correction based on the backlash correction amount (hereinafter referred to as “backlash correction drive”) (S603 in FIG. 7). Then, it is repeatedly determined whether or not the backlash correction drive has been completed (S604 in FIG. 7).

That is, the CPU 17 waits until the backlash correction driving is completed. Therefore, during the backlash correction driving, the control of the charge accumulation in the AF sensor (corresponding to S104 in FIG. 2) is not performed. On the other hand, the CPU 17 determines in FIG.
When it is recognized from the focus detection immediately after the backlash correction that the driving direction needs to be reversed again, the absolute value of the current defocus amount DF [0] is set to the predetermined value IF.
It is determined whether it is equal to or less than th1 (S605 in FIG. 7).

That is, the CPU 17 determines whether or not the absolute value of the current defocus amount DF [0] is within a predetermined range, and such a range is determined by the previous backlash. This is because even if the correction is performed accurately, the defocus amount in the reverse direction may be detected due to the variation in the focus detection. In the present embodiment, the predetermined value IFth1 has a predetermined range of about 0 to 150 [μm].

If the absolute value of the current defocus amount DF [0] is equal to or less than the predetermined value IFth1 as a result of such determination, the photographing lens is controlled under normal lens drive control without excessive drive. It is considered that the reversal of the driving direction was repeated for the fine adjustment of 12. On the other hand, when the absolute value of the current defocus amount DF [0] exceeds the predetermined value IFth1,
It is considered that the previous backlash correction was not properly performed, and excessive driving leading to hunting was performed.

The CPU 17 determines that the absolute value of the current defocus amount DF [0] is the predetermined value IF based on the determination in S605 in FIG.
When it is recognized that it is equal to or less than th1, the backlash correction driving is started (corresponding to S603 in FIG. 7), and it is repeatedly determined whether or not the backlash correction driving is completed (corresponding to S604 in FIG. 7). On the other hand, when the CPU 17 recognizes that the absolute value of the current defocus amount DF [0] exceeds the predetermined value IFth1, the CPU 17 clears the backlash correction permission flag (S606 in FIG. 7) and ends the backlash correction process.

Here, the effects of the present embodiment will be specifically described. For example, the backlash correction causes the photographing lens L1 supposed to be in a state as shown in FIG. 9C (corresponding to FIG. 11C) to receive some force in the right direction, thereby causing the photographing lens L1 to move to the state shown in FIG. C-1) (corresponding to FIG. 11 (C-1)), the photographing lens L1
To return to the lens position a, it is necessary to reverse the driving direction.

The state as shown in FIG. 9 (C-1) corresponds to the case where the driving direction needs to be reversed again by the focus detection immediately after the backlash correction, and the taking lens L1 is moved from the lens position a to the lens position a. Since it has moved to the position c, this also corresponds to the case where the absolute value of the defocus amount exceeds the predetermined value IFth1. Therefore, according to the present embodiment, FIG.
In the state as in (C-1), the backlash correction is prohibited, so that the movement amount of the lens driving member M2 becomes Bk, and the photographing lens L1 returns to the lens position a, and FIG.
-1).

Therefore, in this embodiment, hunting can be avoided since the photographing lens L1 does not cause overrun as shown in FIG. In addition,
In the present embodiment, in the backlash correction permission determination process, the backlash correction permission flag is set when the lens driving amount is equal to or greater than the backlash correction amount. This can be performed in the initialization processing of 2S101, and in such a case, the permission determination processing of the backlash correction can be omitted.

[0060]

As described above, the automatic focusing apparatus according to the first aspect can prohibit the backlash correction when the photographing lens is excessively driven by the backlash correction. Hunting due to excessive driving can be avoided.

The automatic adjusting device according to the second aspect of the invention adjusts the backlash correction when it is recognized from the focus detection result immediately after the backlash correction that the driving direction of the shooting lens needs to be reversed again. Therefore, it is possible to prevent the backlash correction from being erroneously prohibited. Claim 3
The automatic adjustment device described in the above, when it is recognized that the driving direction of the photographing lens needs to be inverted again based on the focus detection result immediately after the backlash correction, and that the defocus amount exceeds a predetermined amount, the photographing lens Is determined to be excessively driven by the backlash correction, so that the backlash correction can be appropriately prohibited.

Therefore, according to the automatic focusing device according to the second and third aspects, hunting due to excessive driving during backlash correction can be reliably avoided.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a still camera.

FIG. 2 is an operation flowchart (1) of the embodiment.

FIG. 3 is an operation flowchart (2) of the embodiment.

FIG. 4 is an operation flowchart (3) of the embodiment.

FIG. 5 is an operation flowchart (4) of the embodiment.

FIG. 6 is an operation flowchart (5) of the embodiment.

FIG. 7 is an operation flowchart (6) of the embodiment.

FIG. 8 is a diagram illustrating an example of a change in the state of a backlash correction permission flag.

FIG. 9 is a diagram illustrating the effect of the embodiment.

FIG. 10 is a diagram illustrating backlash correction.

FIG. 11 is a diagram illustrating a problem in backlash correction.

[Explanation of symbols]

 Reference Signs List 10 camera body 11 interchangeable lens 12 photographing lens 13 main mirror 14 sub mirror 15 AF module 16 sensor drive circuit 17 CPU 18 lens drive control circuit 19 motor 20 encoder 21 operation unit 22 lens information storage circuit 23 lens moving mechanism

Claims (3)

[Claims] A focus detection unit that repeatedly detects a focus of the photographing lens; a lens drive control unit that drives the photographing lens in accordance with a focus detection result by the focus detection unit; and a focus by the focus detection unit. In the process in which the detection of the photographing lens and the driving of the photographing lens by the lens drive control means are repeatedly performed to adjust the focus of the photographing lens, it is necessary to reverse the driving direction of the photographing lens. An automatic focus adjustment device including a backlash correction unit that performs a backlash correction for correcting a driving amount, based on a focus detection result by the focus detection unit immediately after the backlash correction by the backlash correction unit, It is determined whether or not the photographing lens has been excessively driven by the backlash correction. And a backlash correction prohibition unit for prohibiting the backlash correction by the backlash correction unit. 2. The automatic focus adjusting device according to claim 1, wherein the backlash correction prohibiting unit is configured to detect the focus by the focus detection unit immediately after the backlash correction by the backlash correction unit. An automatic focus adjustment device, which determines whether or not the photographing lens has been excessively driven by the backlash correction when recognizing that the reversal of the driving direction is necessary again. 3. The automatic focusing device according to claim 2, wherein the backlash correction prohibiting unit is configured to perform the photographing based on a focus detection result by the focus detection unit immediately after the backlash correction by the backlash correction unit. When it is necessary to reverse the driving direction of the lens again and it is recognized that the defocus amount exceeds a predetermined amount, it is determined that the photographing lens is excessively driven by the backlash correction. Adjustment device.