JP4992761B2 - LENS DRIVE DEVICE AND IMAGING DEVICE - Google Patents

Description

  The present invention relates to a lens driving device and an imaging device.

When it is determined that focus detection is impossible in a camera that performs a focusing operation of a photographic lens using a so-called pupil division phase difference detection method, an operation for searching for a focus-detectable state is performed while moving the photographic lens after a predetermined time has elapsed. One is known (Patent Document 1).

Japanese Patent Laid-Open No. 11-281886

However, if the focus position search operation is prohibited for a predetermined time when focus detection is impossible, there is a problem that even if it is necessary to perform the search operation immediately, it does not operate until the predetermined time elapses.

The problem to be solved by the invention is to provide a lens driving device and an imaging device capable of performing an appropriate search operation.

  The present invention solves the above problems by the following means. In addition, although the code | symbol corresponding to drawing which shows embodiment of this invention is attached | subjected and demonstrated, this code | symbol is only for making an understanding of invention easy, and is not the meaning which limits invention.

The lens driving device according to the invention detects the focus adjustment state of the lens based on the light beam that has passed through the lens (211) provided so as to be able to drive the predetermined range (M1 to M2) along the optical axis (L1) direction. Focus detection means (161-164) for
Position detecting means (260) for detecting the position of the lens;
Drive means (165) for performing a search operation for performing focus detection by the focus detection means while driving the lens when focus detection by the focus detection means is impossible;
Control means (170) for controlling whether to allow the search operation according to the position of the lens detected by the position detection means ,
The predetermined range (M1 to M2) includes a first range (E1 to E2) for adjusting the focus of the lens, and a first range from the first range to a limit end that limits the movement of the lens. 2 ranges (M1-E1, M2-E2),
The control means (170) permits the search operation when the position of the lens by the position detection means is in the second range .

In the lens driving device according to the invention, the control means (170) prohibits the search operation and drives the lens based on the focus adjustment state when the focus detection by the focus detection means is possible. It can be constituted as follows.

The lens driving apparatus according to the present invention further includes start means (150) for starting the focus adjustment operation of the lens based on the focus adjustment state, and the control means (170) is configured to perform the focus adjustment operation by the start means. The search operation is prohibited until the predetermined time (T) elapses after the end of the operation, except when the position of the lens is near the end (M1 to M2) of the predetermined range. Can do.

In this case, the control means (170) may be configured to permit the search operation when a predetermined time (T) has elapsed after the focus adjustment operation by the activation means (150) has been completed. it can.

The imaging device (1) according to the invention includes a lens (211) provided to be able to drive a predetermined range (M1 to M2) along the optical axis direction (L1), and the lens driving device according to the invention. It is characterized by that.

  According to the above invention, an appropriate search operation can be performed.

  In the following, an embodiment in which the above invention is applied to an interchangeable lens single-lens reflex digital camera will be described with reference to the drawings. It can also be applied to fixed cameras.

FIG. 1 is a main part configuration diagram showing a single-lens reflex digital camera 1 according to the present embodiment. Regarding the general configuration of the camera other than the configuration related to the lens driving device and the imaging device of the invention, the illustration and description thereof are one. Omitted.

The single-lens reflex digital camera 1 (hereinafter simply referred to as the camera 1) of the present embodiment includes a camera body 100 and a lens barrel 200, and the camera body 100 and the lens barrel 200 are detachably coupled by a mount unit 300. ing.

The lens barrel 200 incorporates a photographing optical system including a lens group 210 including a focus lens 211 and a zoom lens 212, an aperture device 220, and the like.

The focus lens 211 is provided so as to be movable along the optical axis L <b> 1, and its position is adjusted by the lens driving motor 230 while its position is detected by the encoder 260.

Although the specific configuration of the moving mechanism along the optical axis L1 of the focus lens 211 is not particularly limited, as an example, a rotating cylinder is rotatably inserted into a fixed cylinder fixed to the lens barrel 200, and the inner periphery of the rotating cylinder A helicoid groove (spiral groove) is formed on the surface, and an end of a lens frame for fixing the focus lens 211 is fitted into the helicoid groove. Then, the focus lens fixed to the lens frame moves straight along the optical axis L1 by rotating the rotating cylinder by the lens drive motor 230 or a manual operation by the photographer.

The lens driving motor 230 and the rotating cylinder are connected by a transmission composed of a plurality of gears, for example, and when the driving shaft of the lens driving motor 230 is driven to rotate in any one direction, it is transmitted to the rotating cylinder at a predetermined gear ratio, and When the rotating cylinder rotates in any one direction, the focus lens 211 fixed to the lens frame moves straight in any direction of the optical axis L1. Further, when the drive shaft of the lens drive motor 230 is driven to rotate in the reverse direction, the plurality of gears constituting the transmission also rotate in the reverse direction, and the focus lens 211 moves straight in the reverse direction of the optical axis L1. Note that the focus lens 211 also moves straight in any direction of the optical axis L1 by manually operating the rotating cylinder.

The position of the focus lens 211 is detected by an encoder which is a lens position detector 260. As described above, since the position of the focus lens 211 in the optical axis direction correlates with the rotation angle of the rotating cylinder, it can be obtained by detecting the relative rotation angle of the rotating cylinder with respect to the fixed cylinder of the lens barrel 200, for example. .

As the encoder 260 of this example, a flexible printed circuit board is provided in the circumferential direction of one of the rotating cylinder and the fixed cylinder, and a brush that is in contact with the flexible printed circuit board is provided on the other side. By detecting this, it is possible to exemplify what detects the relative rotation angle of the rotating cylinder with respect to the fixed cylinder.

However, the specific configuration of the encoder is not particularly limited, and the encoder detects the absolute rotation angle of the rotary cylinder with respect to the fixed cylinder, the relative movement amount of the lens frame of the focus lens 211 in the optical axis direction, or the absolute movement angle. What detects a position can also be used.

With such a configuration, the focus lens 211 can move in the direction of the optical axis L1 from the end (closest end) on the camera body side to the end (infinite end) on the subject side by the rotation of the rotating cylinder. it can.

Incidentally, the position information of the focus lens 211 detected by the encoder 260 is transmitted to the lens drive control unit 165 (to be described later) via the lens control unit 250, while the lens drive motor 230 calculates based on this position information. The lens is driven by a drive signal received from the lens drive control unit 165 via the lens control unit 250 toward the focused position.

Here, in the camera 1 of this example, if the focus lens 211 is moved to the close end or the infinite end, the encoder 260 and the like described above may be damaged. The control range 211 is set slightly smaller than the mechanically movable range.

FIG. 3 is a diagram showing the drive range of the focus lens 211 according to this embodiment, and the position of the focus lens 211 is shown on the horizontal axis. As shown in the figure, assuming that the range of mechanical movement of the focus lens 211 by the rotating cylinder described above is from the closest position M1 to the infinite position M2, the lens control unit 250 changes the lens driving motor. The range in which the focus lens 211 can be moved by a command to 230 is set between the closest end position E1 and the infinite end position E2.

Therefore, the focus lens 211 moves within the range from the position E1 to the position E2 so as to move at the position M1 to the position E1, which is the closest end, or at the endless end unless the rotating cylinder is rotated to the closest end or the infinite end by manual operation or the like. It does not move to certain positions M2 to E2. Thereby, the damage by the brush etc. which comprise the encoder 260 moving to the end of both ends can be prevented.

Although details will be described later, the encoder 260 detects the relative position of the focus lens 211 as described above, and the focus lens 211 is at both end regions of the movement range, that is, the closest end shown in FIG. It is also detected whether it is located in the area of positions M1 to E1 or positions M2 to E2 which are infinite ends, or located in the area of positions E1 to E2, and the detection result is sent to the lens controller 250.

  Returning to FIG. 1, the aperture device 220 can adjust the aperture diameter around the optical axis L <b> 1 in order to limit the amount of light that passes through the imaging optical system and reaches the image sensor 110 and to adjust the amount of blur. It is configured. Adjustment of the aperture diameter by the aperture device 220 is performed by transmitting an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 170 to the aperture drive unit 240 via the lens control unit 250, for example. Further, the adjustment of the aperture diameter is performed by a manual operation by the operation unit 150 provided in the camera body 100, and the set aperture diameter is transmitted from the camera control unit 170 to the aperture drive unit 240 via the lens control unit 250. It is also done by. The aperture diameter of the aperture device 220 is detected by an aperture aperture sensor (not shown), and the current aperture diameter is recognized by the lens controller 250.

On the other hand, the camera body 100 includes a mirror system 120 for guiding the light flux from the subject to the image sensor 110, the finder 135, the photometric sensor 137, and the focus detection optical module 161. The mirror system 120 includes a quick return mirror 121 that rotates about a rotation axis 123 by a predetermined angle between the observation position and the shooting position of the subject, and the quick return mirror 121 pivotally supported by the quick return mirror 121. And a sub-mirror 122 that rotates according to the above.

In FIG. 1, a state where the mirror system 120 is at the observation position of the subject is indicated by a solid line, and a state where the mirror system 120 is at the shooting position of the subject is indicated by a two-dot chain line. The mirror system 120 is inserted on the optical path of the optical axis L1 in the state where the subject is in the observation position, while rotating so as to retract from the optical path of the optical axis L1 in the state where the subject is in the photographing position.

The quick return mirror 121 is composed of a half mirror, and in a state where the subject is at the observation position, the quick return mirror 121 reflects a part of the light flux (optical axes L2 and L3) from the subject (optical axis L1). Then, the light is guided to the finder 135 and the photometric sensor 137, and a part of the light beam (optical axis L4) is transmitted and guided to the sub mirror 122. On the other hand, the sub mirror 122 is constituted by a total reflection mirror, and guides the light beam (optical axis L4) transmitted through the quick return mirror 121 to the focus detection optical module 161. The focus detection optical module 161 performs automatic focusing control by a phase difference detection method using subject light, details of which will be described later.

Therefore, when the mirror system 120 is at the observation position, the light beam (optical axis L1) from the subject is guided to the finder 135, the photometric sensor 137, and the focus detection optical module 161, and the subject is observed and exposed. Calculation and detection of the focus adjustment state of the focus lens 211 are executed. When the photographer fully presses the release button, the mirror system 120 rotates to the photographing position, and all the luminous flux (optical axis L1) from the subject is guided to the image sensor 110, and the photographed image data is stored in a memory (not shown). .

The image sensor 110 is fixed on the camera body 100 at a position on the optical axis L1 of the light flux from the subject and serving as a planned focal plane of the photographing optical system 210. The imaging element 110 is a two-dimensional array of a plurality of photoelectric conversion elements, and can be configured by a two-dimensional CCD image sensor, a MOS sensor, a CID, or the like. The electrical image signal photoelectrically converted by the image sensor 110 is subjected to image processing by the camera control unit 170 and then stored in a memory (not shown). Note that the memory for storing the photographed image can be constituted by a built-in memory or a card-type memory.

On the other hand, the subject light reflected by the quick return mirror 121 forms an image on a focusing screen 131 disposed on a surface optically equivalent to the image sensor 110, and the photographer's light passes through the pentaprism 133 and the eyepiece 134. Guided to the eyeball. At this time, the transmissive liquid crystal display 132 superimposes and displays a focus detection area mark on the subject image on the focusing screen 131, and information relating to shooting such as a shutter speed, an aperture value, and the number of shots in an area outside the subject image. Is displayed. As a result, the subject, its background, photographing related information, and the like can be observed through the finder 134 in a state where the release is not performed.

In addition, a photometric lens 136 and a photometric sensor 137 are provided in the vicinity of the eyepiece lens 134 to receive part of the subject light imaged on the focusing screen 131.

The photometric sensor 137 is composed of a two-dimensional color CCD image sensor or the like, and divides the photographing screen into a plurality of regions and outputs a photometric signal corresponding to the luminance of each region in order to calculate an exposure value at the time of photographing. The photometric signal detected by the photometric sensor 137 is output to the camera control unit 170 and used for exposure control.

The operation unit 150 is a shutter release button or an input switch for the photographer to set various operation modes of the camera 1. Switching between the autofocus mode / manual focus mode and the autofocus mode also includes a one-shot mode / continuous mode. It is possible to switch between the numeric modes. In addition to the shutter being turned on when the shutter release button is fully pressed, the focusing operation of the focus lens is turned on when the button is half-pressed in the autofocus mode, and turned off when the button is released. Various modes set by the operation unit 150 are transmitted to the camera control unit 170.

The camera body 100 is provided with a camera control unit 170. The camera control unit 170 includes peripheral components such as a microprocessor and a memory, and is electrically connected to the lens control unit 250 through an electric signal contact unit provided in the mount unit 300, and receives lens information from the lens control unit 250. At the same time, information such as the defocus amount and aperture diameter is transmitted to the lens controller 250. The camera control unit 170 reads out image information from the image sensor 110 as described above, performs predetermined information processing as necessary, and outputs the information to a memory (not shown). The camera control unit 170 controls the entire camera 1 such as correction of captured image information and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 200.

The focus detection optical module 161 of this example is a phase difference type focus detection element, which is on the optical axis L4 of the light beam reflected by the sub-mirror 122 and at a position optically equivalent to the image pickup surface of the image pickup element 110. It is fixed.

FIG. 2 is a diagram showing the configuration of the focus detection module 161 shown in FIG. 1. The focus detection module 161 of this example includes a condenser lens 161a, a diaphragm mask 161b having a pair of openings, and a pair of re-imaging lenses. 161c and a pair of line sensors 161d, and focus adjustment is performed by obtaining a phase shift between a pair of image signals obtained by the line sensor 16 receiving a pair of light beams passing through a pair of different areas of the exit pupil of the photographing lens 211. Detect state.

As shown in the figure, when the subject P forms an image on the equivalent surface (scheduled imaging surface) 161e of the image sensor 110, the focused state is reached, but the imaging lens (focus lens) 211 moves in the direction of the optical axis L1. Thus, when the image forming point is shifted from the equivalent surface 161e toward the subject (referred to as a front pin) or shifted toward the camera body 100 (referred to as a rear pin), the focus is shifted.

When the imaging point of the subject P is shifted from the equivalent surface 161e toward the subject, the interval W between the pair of image signals detected by the pair of line sensors 161d becomes shorter than the interval W in the focused state, and vice versa. If the imaging point of the subject image P is shifted to the camera body 100 side, the interval W between the pair of image signals detected by the pair of line sensors 161d becomes longer than the interval W in the focused state.

That is, in the in-focus state, the image signals detected by the pair of line sensors 161d overlap with the center of the line sensor, but in the out-of-focus state, each image signal is shifted from the center of the line sensor, that is, the phase difference is increased. Therefore, focusing is performed by moving the focus lens 211 by an amount corresponding to the phase difference (deviation amount).

Returning to FIG. 1, the AF-CCD control unit 162 controls the gain and accumulation time of the line sensor of the focus detection optical module 161 in the autofocus mode, and stores information on the focus detection area selected as the focus detection position. A pair of image signals received from the camera control unit 170 and detected by the pair of line sensors corresponding to the focus detection area are read and output to the defocus calculation unit 163.

The defocus calculation unit 163 converts the shift amount of the pair of image signals sent from the AF-CCD control unit 162 into a defocus amount ΔW, and outputs this to the lens drive amount calculation unit 164.

The lens drive amount calculation unit 164 calculates a lens drive amount Δd corresponding to the defocus amount ΔW based on the defocus amount ΔW sent from the defocus calculation unit 163, and supplies this to the lens drive control unit 165. Output.

The lens drive control unit 165 sends a drive command to the lens drive motor 230 based on the lens drive amount Δd sent from the lens drive amount calculation unit 164, and moves the focus lens 211 by the lens drive amount Δd.

  Incidentally, there are cases where the reliability of the defocus amount calculated based on the image signal detected by the line sensor 161d of the focus detection module 161 is low, as in the case where the contrast of the focus detection area is small. Therefore, the defocus calculation unit 163 determines whether or not the contrast of the pair of image signals sent from the AF-CCD control unit 162 is equal to or higher than a predetermined threshold value.

If it is determined that the focus cannot be detected, the focus lens 211 is driven in a predetermined direction along the optical axis L1, and a pair of image signals from the line sensor 161d is output at a predetermined time interval by the focus detection module 161 during this time. The read / defocus calculation unit 163 determines whether the contrast is equal to or higher than a predetermined threshold. Then, the AF-CCD control unit 162 and the defocus amount calculation unit 163 calculate the defocus amount based on the pair of image signals for which the contrast is determined to be equal to or greater than a predetermined threshold. Such a focus detection operation performed when focus detection is impossible is referred to as a search operation.

  However, if the search operation is performed even if it is determined that the focus detection is impossible immediately after the automatic focusing operation is turned on by half-pressing the release button, it is turned off again due to an erroneous operation of the photographer, for example. In this case, if the focus detection is impossible, the search operation is started immediately. For this reason, in the camera 1 of this example, the search operation is prohibited until a predetermined time T elapses after the automatic focusing operation by half-pressing the release button is changed from OFF to ON. These release button ON / OFF detection, timing processing, and search operation prohibition commands are detected and calculated by the camera control unit 170 and output to the lens drive control unit 165.

  On the other hand, even before the predetermined time T has elapsed after the automatic focusing operation by pressing the release button halfway from OFF to ON, depending on the lens position of the focus lens 211, the focusing position is near the position. It may be clear that it does not exist. For example, as shown in FIG. 3, the end of the focus position on the near side of the focus lens 211 is set to the infinite side from the electrical limit end E1 in order to cope with the change in the focus position of the focus lens 211 due to the influence of temperature change or the like. In addition, the end of the infinite focusing position is set closer to the electrical limit end E2 for the same reason. Therefore, when the focus lens 211 is in the closest range M1 to E1 or the infinite range M2 to E2 by the photographer's manual operation or the like, it is clear that there is no in-focus position near that position. .

In the camera 1 of this example, the current position of the focus lens 211 is detected by the encoder 260, and the focus lens 211 is detected by the camera control unit 170 via the lens control unit 250, or the infinite end range M1 to E1. It is determined whether or not M2 to E2.

When the focus lens 211 is not in the closest range M1 to E1 or the infinite range M2 to E2, that is, when the focus lens 211 is in the electrical limit end E1 to E2, the search operation is prohibited and the position is determined. The defocus amount at is calculated. On the other hand, when the focus lens 211 is in the near end range M1 to E1 or the infinite end range M2 to E2, the search operation is performed even when the search operation prohibition command is being output, and the focus lens is in the in-focus position. 211 is driven.

That is, the camera 1 of this example detects the light flux that has passed through the focus lens 211 stopped at a certain position by the focus detection module 161, calculates the defocus amount based on the obtained pair of image signals, A focusing operation is performed by driving the focus lens 211 by a drive amount corresponding to the defocus amount. In this case, depending on the image signal detected by the focus detection module 161, when a highly reliable defocus amount cannot be obtained, it is determined that focus detection is impossible, and the above-described search operation is performed to achieve high reliability. Calculate the defocus amount.

However, as a general rule, the search operation is prohibited until the predetermined time T elapses after the automatic focusing operation by half-pressing the release button is changed from OFF to ON, but the focus lens 211 is in the range M1 to E1 at the closest end or In the infinite range M2 to E2, the search operation is performed even when the search operation prohibition command is being output, and the focus lens 211 is driven to the in-focus position.

Next, the operation will be described.

FIG. 4 is a flowchart showing main operations of the camera 1 according to this embodiment.

First, in step S1, it is determined whether the power of the camera 1 is turned on. If it is turned on, the process proceeds to step S2, and if it is turned off, the process is repeated until the power is turned on. In the following description, it is assumed that the autofocus mode / manual focus mode changeover switch included in the operation unit 150 is set to the autofocus mode.

In step S2, the focus detection module 161 detects a light beam that has passed through the focus lens 211 stopped at a certain position and outputs a pair of image signals. The AF-CCD control unit 162 and the defocus calculation unit 163 A defocus amount ΔW is calculated based on the obtained pair of image signals. In step S3, the lens drive amount calculation unit 164 calculates a lens drive amount Δd (corresponding to the lens target position) based on the calculated defocus amount ΔW, and outputs this to the lens drive control unit 165. .

In step S2, the defocus amount calculation unit 163 determines whether the contrast of the image signal detected by the focus detection module 161 is equal to or greater than a predetermined threshold value. On the other hand, if it is less than the predetermined threshold, it is determined that focus detection is impossible.

In step S4, it is determined whether or not the release button of the operation unit 150 is half-pressed and the automatic focusing operation is ON. If it is not half-pressed and is OFF, the process proceeds to step S5. Proceed to step S12. Hereinafter, the state where the release button is half-pressed is also referred to as the AF switch is ON, and the state where the release button is released is also referred to as the AF switch is OFF.

In step S5, it is determined whether or not the AF switch is ON in the previous routine. If the AF switch is ON, the process proceeds to step S6. If the AF switch is OFF, the process proceeds to step S7A. In step S7A, it is determined whether or not the timekeeping in step S6 has been started. If timekeeping has started, the process proceeds to step S7B and continues to be timed. If timekeeping has not been started, steps S7B and S8 are started. , S9 are jumped to and the process proceeds to step S11 to permit the search operation.

In the process from step S4 to step S5, when the AF switch is turned from OFF to ON, in step S6, the camera control unit 170 starts a timing process from the time when the AF switch is turned off. In addition, when starting the time measuring process in step S6, if the time measuring process has been continued until then, it is terminated and a new time measuring process is started.

Then, it is determined whether or not the time counted in the subsequent step S8 is within a predetermined time T determined in advance. If the time exceeds the predetermined time T, the process proceeds to step S11 and the search operation is permitted. In this case, since the predetermined time T has already passed since the AF switch was turned on, when the focus detection is impossible, there is no sense of incongruity for the photographer even if focus detection is performed by the search operation, but rather due to low contrast or the like. An appropriate and quick focusing operation can be performed by performing a search operation corresponding to the inability to detect the focus.

On the other hand, if the time being measured is within the predetermined time T, the process proceeds to step S9, and based on the detection signal from the encoder 260, the current position of the focus lens 211 is in the range M1 to E1 at the closest end or It is determined whether or not it is in the endless range M2 to E2.

If the camera control unit 170 determines that the focus lens 211 is in either the near end range M1 to E1 or the infinite end range M2 to E2, the process proceeds to step 11 and permits the search operation. When the focus lens 211 is positioned outward from the end of the focus position, the focus position does not exist in the vicinity of the focus position, so that the prohibition of the search operation is canceled and the search operation is immediately executed. Thereby, useless waiting time due to prohibition of the search operation can be reduced, and focusing can be performed in a short time.

On the other hand, if it is determined in step S9 that the focus lens 211 is not in either the near end range M1 to E1 or the infinite end range M2 to E2, the process proceeds to step 10 and step S22, and the search operation is performed. The focus lens 211 is stopped. Thus, even when the photographer erroneously turns off the AF switch and turns it on again, the search operation is not performed, and an automatic focusing operation unintended by the photographer can be prevented.

Returning to step S4, if the AF switch is ON, the process proceeds to step S12, where it is determined whether or not the time measurement in step S6 has been started. If the time measurement has started, the process proceeds to step S13 and the time measurement is continued. On the other hand, if the timing has not been started, the process jumps to steps S13, S14, and S15 and proceeds to step S17 to permit the search operation.

Here, the case of passing through steps S4 → S12 → S13 → S14 is a state in which the process of step S6 has been executed in the routine before the previous time because the timing has already been started. That is, after the power is turned on, the AF switch is turned from ON to OFF to ON.

In this case, in the following step S14, it is determined whether or not the measured time is within a predetermined time T, and if it exceeds the predetermined time T, the process proceeds to step S17 and the search operation is permitted. . When the process proceeds to step S17 as described above, since the predetermined time T has already elapsed since the AF switch was turned on, if the focus detection is impossible, the photographer does not feel uncomfortable even if the focus detection is performed by the search operation. Rather, an appropriate and quick focusing operation can be performed by performing a search operation corresponding to the inability to detect the focus due to low contrast or the like.

On the other hand, if the measured time is within the predetermined time T, the process proceeds to step S15, and based on the detection signal from the encoder 260, the current position of the focus lens 211 is within the range M1 to E1 at the closest end or It is determined whether or not it is in the endless range M2 to E2.

In step S15, if the camera control unit 170 determines that the focus lens 211 is in either the near end range M1 to E1 or the infinite end range M2 to E2, the process proceeds to step 17 and permits the search operation. . When the focus lens 211 is positioned outward from the end of the focus position, the focus position does not exist in the vicinity of the focus position, so that the prohibition of the search operation is canceled and the search operation is immediately executed. Thereby, useless waiting time due to prohibition of the search operation can be reduced, and focusing can be performed in a short time.

On the other hand, if it is determined in step S15 that the focus lens 211 is not in either the near end range M1 to E1 or the infinite end range M2 to E2, the process proceeds to step 16 and the search operation is prohibited. Thus, even when the photographer erroneously turns off the AF switch and turns it on again, the search operation is not performed, and an automatic focusing operation unintended by the photographer can be prevented.

On the other hand, the case of passing through steps S4 → S12 → S17 is a state in which the AF switch is kept on after the power is turned on because the timing has not yet started. Therefore, if this routine is passed, the search operation is permitted in step S17, and if focus detection is impossible, the search operation is immediately executed.

In the next step S18, the defocus amount calculation unit 163 determines whether or not focus detection is possible based on the contrast of the image signal detected by the focus detection module 161, and if this contrast is equal to or greater than a predetermined threshold value. Proceed to step S19. In step S19, the lens drive control unit 165 drives the lens drive motor 230 via the lens control unit 250, and drives the focus lens 211 toward the in-focus position. That is, when the AF switch is turned on and focus detection is possible, the focusing operation is performed by detecting the phase difference at that position.

On the other hand, if it is determined in step S18 that focus detection is impossible, the process proceeds to step S20, and it is determined whether the prohibition or permission of the search operation in steps S16 and S17 is valid. If the search operation is prohibited, the process proceeds to step S22, the focus lens 211 is stopped (if it is already stopped, the state is maintained), and the process returns to step S1.

On the other hand, if the search operation is permitted in step S20, the process proceeds to step S21, the focus lens 211 is driven to the initial position of the search operation, and the search operation in a predetermined direction is started from here. During this time, the focus detection module 161 reads a pair of image signals from the line sensor 161d at a predetermined time interval, and the defocus calculation unit 163 determines whether the contrast is equal to or higher than a predetermined threshold.

When it is determined that the contrast of the pair of image signals is equal to or greater than a predetermined threshold, the focus lens is stopped, and the AF-CCD control unit 162 and the defocus amount calculation unit 163 calculate the defocus amount. When the defocus amount is calculated, the lens drive amount calculation unit 164 calculates the lens drive amount corresponding to the defocus amount, drives the lens drive motor 230 via the lens drive control unit, and moves toward the in-focus position. The focus lens 211 is driven.

As described above, according to the camera 1 of the present embodiment, when the prohibition of the search operation is necessary, the search operation is permitted when the prohibition of the search operation is unnecessary. Operation can be performed.

In the above-described embodiment, the prohibition and permission of the search operation are controlled depending on whether the focus lens 211 is in the closest range M1 to E1 or the infinite range M2 to E2. When it is considered that there is no focus lens in the vicinity of the position, the search operation can be permitted. For example, when the shooting mode is set to the distant view mode and the focal length is large but the focus lens is on the close side, it is expected that there is no in-focus position in the vicinity. Operation can be permitted.

In the above-described embodiment, the start time of the search operation prohibition time is set to the time when the AF switch is turned off. However, the time measurement processing can be started from the time when the AF switch is turned on. Alternatively, the elapsed time from the time point when the defocus amount calculation unit 163 determines that focus detection is impossible can be timed, and the search operation prohibition time can be controlled based on this.

It is a principal part block diagram which shows the single-lens reflex digital camera which concerns on embodiment of invention. It is a figure which shows the structure of the focus detection module shown in FIG. It is a figure which shows the drive range of the focus lens shown in FIG. It is a flowchart which shows the main operation | movement of the camera shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single-lens reflex digital camera 100 ... Camera body 110 ... Image pick-up element 161 ... Focus detection module 162 ... AF-CCD control part 163 ... Defocus calculating part 164 ... Lens drive amount calculating part 165 ... Lens drive control part 170 ... Camera control part 200 ... Lens barrel 210 ... Lens group 220 ... Aperture device 230 ... Lens drive motor 240 ... Aperture drive device 250 ... Lens control unit 260 ... Encoder

Claims (5)

A focus detection means for detecting a focus adjustment state of the lens based on a light beam that has passed through a lens that can be driven in a predetermined range along the optical axis direction;
Position detecting means for detecting the position of the lens;
Drive means for performing a search operation for performing focus detection by the focus detection means while driving the lens when focus detection by the focus detection means is impossible;
Control means for controlling whether or not to allow the search operation according to the position of the lens detected by the position detection means ,
The predetermined range includes a first range for adjusting the focus of the lens, and a second range up to a limit end that is located outside the first range and restricts the movement of the lens.
The lens driving device according to claim 1, wherein the control unit permits the search operation when the position of the lens detected by the position detection unit is in the second range . The lens driving device according to claim 1 ,
When the focus detection by the focus detection unit is possible, the control unit prohibits the search operation and drives the lens based on the focus adjustment state. The lens driving device according to claim 1 or 2 ,
An activation means for activating a focus adjustment operation of the lens based on the focus adjustment state;
The control means prohibits the search operation until a predetermined time elapses after the focus adjustment operation by the activation means is completed, unless the position of the lens is in the vicinity of the end of the predetermined range. A lens driving device. The lens driving device according to claim 3 ,
The lens drive device according to claim 1, wherein the control unit permits the search operation when a predetermined time has elapsed after the focus adjustment operation by the activation unit is completed. A lens provided to drive a predetermined range along the optical axis direction;
Imaging apparatus characterized by comprising a lens driving device according to any one of claims 1-4.

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