JP3610093B2 - Imaging device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an imaging apparatus, and more particularly to automatic focusing control in an imaging apparatus equipped with a wide attachment lens.
[0002]
[Prior art]
FIG. 4 is a schematic configuration diagram of an inner focus type lens system equipped with a wide attachment lens unit. In FIG. 4, 101 is a fixed first fixed lens group, 102 is a variable power lens group that performs zooming, 103 is a stop, 104 is a fixed second fixed lens group, and 105 is a focus adjustment function and variable. A lens group having a so-called competition function (hereinafter referred to as a focus competition lens) 106 that corrects the movement of the focal plane due to magnification, and 106 is an image sensor (CCD).
[0003]
Reference numeral 122 denotes a wide attachment lens that can be attached and detached on the same optical axis as the inner focus type lens system. When this lens is mounted, the focal length of the lens system is changed, and the enlargement ratio is changed. As is well known, in the lens system configured as shown in FIG. 4, the focus lens 105 has both a focus adjustment function and a competition function. Therefore, even when the focal lengths are equal, the imaging surface (imaging device) 106 is focused. The position of the focus competition lens 105 for doing so differs depending on the subject distance.
[0004]
When the subject distance is changed at each focal length when the wide attachment lens 122 is not attached, the position of the focus competition lens 105 for focusing on the image sensor 106 is continuously plotted as shown in FIG. become. Accordingly, during zooming operation, the locus shown in FIG. 5 is selected according to the subject distance, and the focus lens 105 is moved according to the selected locus, thereby enabling zooming without blur.
[0005]
On the other hand, when the wide attachment lens 122 is attached, the trajectory shown in FIG. 5 changes as shown in FIG. In other words, when the wide attachment lens 122 is attached, the locus corresponding to each subject distance is shifted to the closest side and the shape of the locus is changed as compared with the case where the wide attachment lens 122 is not attached.
[0006]
Therefore, in order to perform zooming without blur during zooming with the wide attachment lens 122 attached, it is necessary to perform zooming control different from that when the wide attachment lens 122 is not attached. As shown in FIG. 6, on the telephoto side from the focal distance 602, the locus diverges out of the focusable area according to the subject distance, so that focusing is impossible. For this reason, when the wide attachment lens 122 is attached, the zoom lens group 102 is generally fixed at the wide end position and the zoom operation is prohibited.
[0007]
As a conventional automatic focusing (AF) control method, generally, a high-frequency component of a video signal obtained from an image sensor 106 such as a CCD is extracted, and the high-frequency component is used as an AF evaluation value. A so-called hill-climbing method is employed in which the focus compensator 105 is driven to adjust the focus so as to be maximized.
[0008]
[Problems to be solved by the invention]
However, as is apparent from the above description, even when the subject at a certain distance is in focus, the subject at the same distance is attached or removed (that is, the wearing state is changed) when the wide attachment lens 122 is attached. As a result, the position of the focus lens 105 for in-focusing changes and blurring occurs.
[0009]
However, conventionally, an AF evaluation value signal in the blurred state is captured, and it is determined whether or not the focus control is restarted based on the AF evaluation value signal, that is, whether or not to move the focus compensator 105 again. Since the focus was corrected, it took a long time to achieve focusing.
[0010]
In addition, even when the focus direction is determined during the AF operation, such as when the attachment is wide due to the attachment of the wide attachment lens 122, the AF evaluation value signal cannot be sufficiently changed and the blurring may stop. There is also a problem that the time to focus is delayed because the focus direction is misjudged and blurring is increased.
[0011]
The present invention has been made under such a background, and an object of the present invention is to quickly eliminate blurring that occurs when the mounting state of a wide attachment lens (lens for changing the focal length and magnification) is changed. It is to be resolved.
[0012]
[Means for Solving the Problems]
To achieve the above object, the present invention 請 Motomeko 1 described, the same on the optical axis between the first lens group for performing focus adjustment (corresponding to the focus compensation lens 105), the changing the focal length 2 A lens system (corresponding to the wide attachment lens 122), and a sharpness signal corresponding to the degree of focus from a video signal obtained by photoelectrically converting an optical subject image formed through the lens system. Focusing control means (corresponding to AF evaluation value processing circuit 117, AF microcomputer 115, driver 120, and motor 121) that performs focusing control by extracting and controlling movement of the first lens group based on the sharpness signal ) And restarting means (AF Myco) for moving the first lens group and restarting focus control by the focus control means when the mounting state of the second lens group is changed. And a corresponding) to 115.
[0013]
To achieve the above object, in the invention of claim 2 Symbol placement, the restart means definitive to claim 1, comprising a detecting means for detecting a change in the mounting state of the second lens group, said detection means Thus, when a change in the mounting state of the second lens group is detected, the first lens group is moved, and the focusing control by the focusing control means is restarted.
[0014]
To achieve the above object, in the invention of claim 3 Symbol mounting, said restart means definitive in claim 1, when the mounting state of the second lens group is changed, the predetermined direction in accordance with the change state The first lens group is moved to restart the focusing control by the focusing control means.
[0015]
To achieve the above object, in the invention of claim 4 Symbol mounting, said restart means definitive in claim 3, when the second lens group is changed to the non-wearing state from the mounting state in the direction of infinity, When the non-wearing state is changed to the wearing state, the first lens group is moved in the closest direction, and the focus control by the focus control means is restarted.
[0016]
[Action]
In the invention of claim 1 Symbol placement, the focusing control unit extracts a sharpness signal corresponding to a focusing degree from a video signal where the optical subject image photoelectrically converts formed through the lens system, Focus control is performed by controlling movement of the first lens group based on the sharpness signal, and the restarting means changes the first lens group when the mounting state of the second lens group is changed. By moving the lens group and restarting the focus control by the focus control means, the blur that occurs when the mounting state of the second lens group is changed is quickly eliminated.
[0017]
In the present invention of claim 2 Symbol placement, the restart means definitive to claim 1, comprising a detecting means for detecting a change in the mounting state of the second lens group, the second lens group by said detection means When the change in the mounting state of the second lens group is detected, the mounting state of the second lens group is changed by moving the first lens group and restarting the focusing control by the focusing control means. When this happens, the blur that occurs can be resolved quickly.
[0018]
In the invention of claim 3 Symbol mounting, said restart means definitive in claim 1, when the mounting state of the second lens group is changed, the first lens group in a predetermined direction corresponding to the change state By moving the lens and restarting the focusing control by the focusing control means, the blur that occurs when the mounting state of the second lens group is changed can be quickly and reliably eliminated.
[0019]
In the invention of claim 4 Symbol mounting, said restart means definitive to claim 3, in the case where the second lens group is changed to the non-wearing state from the mounting state infinity direction, in the mounted state from the non-attached state When changed, it occurs when the mounting state of the second lens group is changed by moving the first lens group in the closest direction and restarting the focus control by the focus control means. Eliminate blurring quickly and reliably.
[0020]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is a schematic configuration diagram of a video integrated camera to which an imaging apparatus according to an embodiment of the present invention is applied.
[0022]
In FIG. 1, reference numerals 101 to 105 are components of the inner focus type lens system described with reference to FIG. 4, 101 is a fixed first fixed lens group, and 102 is a variable power lens group that performs variable power. , 103 is a stop, 104 is a fixed second fixed lens group, 105 is a lens group having a focus adjustment function and a so-called competition function for correcting movement of the focal plane due to zooming (hereinafter referred to as a focus competition lens). It is.
[0023]
The image light transmitted through this lens system forms an image on the image sensor 106 and is converted into an image signal by photoelectric conversion. Reference numeral 107 denotes an amplifier or impedance converter, and reference numeral 108 denotes a camera signal processing circuit. The video signal processed here is amplified to a specified level by the amplifier 109, processed by the LCD display circuit 110, and then used as an electronic viewfinder. A captured image is displayed on the LCD 111.
[0024]
On the other hand, the video signal amplified by the amplifier 107 is also output to the aperture control circuit 112 and the AF evaluation value processing circuit 117. The aperture control circuit 112 controls the aperture 103 by driving the IG driver 113 and the IG meter 114 in accordance with the video signal input level to adjust the light amount.
[0025]
The AF evaluation value processing circuit 117 extracts only the high-frequency component of the video signal in the distance measurement frame in accordance with the gate signal from the frame generation circuit 116 corresponding to the distance measurement frame, and obtains the sharpness corresponding to the focus degree. It is supplied to the AF microcomputer 115 as an AF evaluation value signal. The AF microcomputer 115 performs lens drive control, range-finding frame control for changing the range-finding area, and the like according to the degree of focus indicated by the AF evaluation value signal.
[0026]
Reference numerals 118 and 120 denote drivers for outputting driving energy to the lens driving motor in accordance with driving instructions for the variable power lens group 102 and the focal lens 105 output from the AF microcomputer 115, respectively. These are motors for driving the variable power lens group 102 and the focal component lens 105 in the optical axis direction, respectively.
[0027]
When a stepping motor is employed as the lens driving motor, the lens is driven as follows. That is, the AF microcomputer 115 outputs a motor rotation frequency signal corresponding to the lens moving speed and a motor rotation direction signal corresponding to the lens driving direction to the motor drivers 118 and 120. The motor drivers 118 and 120 set the phases of the four motor excitation phases to forward rotation or reverse rotation according to the rotation direction signal, and apply voltages of the four motor excitation phases according to the rotation frequency signal. By outputting while changing (or current), the rotation direction and the rotation frequency of the motor are controlled. As a result, the stepping motors 119 and 121 are rotated to drive the lens.
[0028]
A wide attachment lens 122 is detachably attached to the optical axis of the lens system by a lens slide mechanism 123 as indicated by a broken line in FIG. The lens attachment detection switch 124 detects whether the wide attachment lens 122 is in the attached state or the non-attached state, and the detection signal is supplied to the AF microcomputer 115.
[0029]
[First embodiment]
Next, the focusing operation algorithm in the first embodiment will be described with reference to the flowchart of FIG.
[0030]
First, the AF microcomputer 123 captures an AF evaluation value signal from the AF evaluation value processing circuit 117 while slightly vibrating the focus lens 105 by a wobbling operation (step S1), and is the in-focus state or being out of focus (step S1)? When it is out of focus, it is determined whether it is a front pin or a rear pin (step S2). As a result, when the subject is out of focus and is out of focus, a mountain climbing operation in the direction of the determination result by the wobbling operation is executed (step S3). Then, it is determined whether or not the focal point, that is, the vertex of the AF evaluation value signal has been exceeded (step S4). If not, the process returns to step S3 to continue the hill climbing operation.
[0031]
On the other hand, if the vertex of the AF evaluation value signal is exceeded, an operation of returning the focus lens 105 to that vertex is performed (step S5), and it is determined whether or not the vertex of the AF evaluation value signal has been reached (step S6). ). As a result, if the vertex has not been reached, the operation returns to step S5 and returns to the vertex. On the other hand, when the vertex is reached, the subject may change due to panning or the like during the operation of returning to the vertex of the AF evaluation value signal. In order to restart the focus control, the process returns to step S1 to perform the wobbling operation.
[0032]
If it is determined in step S2 that the subject is in focus as a result of the wobbling operation, the focus compensator 105 is stopped, and the process proceeds to a restart monitoring routine in step S7 and subsequent steps. That is, first, in step S7, the AF evaluation value signal level at the time of focusing is stored. Then, based on the detection signal from the lens attachment detection switch 124, it is determined whether or not the attachment state of the wide attachment lens 122 has changed (step S8). Here, the change in the wearing state means whether the wide attachment lens 122 is changed from the non-attached state to the attached state, or whether the wide attachment lens 122 is changed from the attached state to the non-attached state.
[0033]
When the mounting state of the wide attachment lens 122 changes, as described in the section of the conventional example, the position of the focus competition lens 105 that focuses on a subject at a predetermined distance changes as the mounting state of the wide attachment lens 122 changes. Therefore, it is necessary to restart the focus compensator 105 to find a new in-focus point. Therefore, when it is determined in step S8 that the mounting state of the wide attachment lens 122 has changed, the process returns to step S1 to perform a wobbling operation, and focus control is performed again.
[0034]
On the other hand, if the mounting state of the wide attachment lens 122 has not changed, the normal restart monitoring process of step S9 is performed. That is, by checking whether the current AF evaluation value signal level fluctuates in comparison with the AF evaluation value signal level at the time of focusing stored in step S7 (step S9), it is determined whether or not to restart. Is determined (step S10). For example, when the current AF evaluation value signal level fluctuates by a predetermined percentage or more with respect to the stored AF evaluation value signal level at the time of in-focus, it is assumed that the subject has changed due to panning or the like and “restart”. If the change is less than a predetermined percentage, it is determined that the subject has not changed and “do not restart”.
[0035]
If it is determined in step S10 that "do not restart", the focus compensator 105 is stopped as it is (step S11), the process returns to step S8, and restart monitoring is performed again. On the other hand, when it is determined to “restart”, the process returns to step S1, and the wobbling operation is performed again to perform focusing control. By repeating such an operation, the movement of the focus lens 105 is controlled so that the in-focus state can be constantly maintained.
[0036]
As described above, when the mounting state of the wide attachment lens 122 is changed, the focus control is forcibly restarted without performing the restart monitoring based on the AF evaluation value signal, thereby performing the focus control in the AF process. It is possible to save time for determining whether or not to perform restart and improve responsiveness. In other words, when determining the restart of the focusing control based on the AF evaluation value signal, after the mounting state of the wide attachment lens 122 is changed, the high frequency component in the changed state is taken in and determined. A predetermined time is required until the start is executed. If the restart is forcibly executed when the mounting state of the wide attachment lens 122 is changed as described above, in other words, at the moment when the mounting state is changed. Then, restart is executed while the AF evaluation value signal is generated based on the video signal after the mounting state of the wide attachment lens 122 is changed, and the blurring generated when the mounting state is changed can be quickly detected. Can be resolved.
[0037]
[Second Embodiment]
Next, the focusing operation algorithm in the second embodiment will be described with reference to the flowchart of FIG. The first embodiment is an example in which blurring caused by a change in the mounting state is quickly eliminated by forcibly restarting when the mounting state of the wide attachment lens 122 is changed. The second embodiment Is an example in which blurring that occurs when the mounting state changes can be resolved more quickly and reliably by forcibly climbing the mountain in the in-focus direction according to the change in the mounting state.
[0038]
The AF microcomputer 123 first determines whether or not the mounting state of the wide attachment lens 122 has changed based on the detection signal from the lens mounting detection switch 124 (step S21). As a result, when the wearing state changes, it is determined whether or not the change is a change from non-wearing (OFF) to wearing (ON) (step S22).
[0039]
As a result, if the change is from non-mounting (OFF) to mounting (ON), the moving direction of the focus lens 105 is set to the closest direction (step S23), and the process proceeds to step S28 described later. On the other hand, if the change is from mounting (ON) to non-mounting (OFF), the moving direction of the focus lens 105 is set to an infinite direction (step S24), and the process proceeds to step S28. Note that the setting of the moving direction of the focus lens 105 according to the change in the mounting state of the wide attachment lens 122 is the same subject when the wide attachment lens 122 is mounted as shown in FIG. This is done considering that the position of the focus lens 105 that focuses on the distance shifts in the closest direction.
[0040]
If it is determined in step S21 that the mounting state of the wide attachment lens 122 has not changed, an AF evaluation value signal is captured from the AF evaluation value processing circuit 117 while the focus lens 105 is vibrated slightly by a wobbling operation ( In step S25), it is determined whether the current focus is in focus or the image is out of focus (if the image is out of focus, whether it is the front pin or the rear pin) (step S26). As a result, when the image is out of focus and out of focus, the direction of the determination result by the wobbling operation is set as the movement direction (mountain climbing operation direction) of the focus lens 105 (step S27), and the process proceeds to step S28.
[0041]
In step S28, the mountain climbing operation in the direction set in step S23, 24, or 28 is executed. Then, it is determined whether or not the focal point, that is, the vertex of the AF evaluation value signal has been exceeded (step S29). If not, the process returns to step S28 to continue the mountain climbing operation.
[0042]
On the other hand, if the vertex of the AF evaluation value signal has been exceeded, an operation of returning the focus lens 105 to that vertex is performed (step S30), and it is determined whether or not the vertex of the AF evaluation value signal has been reached (step S31). ). As a result, if the vertex has not been reached, the operation returns to step S5 and returns to the vertex. On the other hand, when the vertex is reached, the subject may change due to panning or the like during the operation of returning to the vertex of the AF evaluation value signal. In order to restart the focusing control, the process returns to step S21 to monitor the mounting state of the wide attachment lens 122, perform a wobbling operation, and the like.
[0043]
If it is determined in step S26 that the subject is in focus as a result of the wobbling operation, the focus compensator 105 is stopped, and the process proceeds to a restart monitoring routine in step S32 and subsequent steps. That is, first, in step S32, the AF evaluation value level at the time of focusing is stored. Based on the detection signal from the lens mounting detection switch 124, it is determined whether or not the mounting state of the wide attachment lens 122 has changed (step S33).
[0044]
As a result, when the mounting state changes, the process proceeds to step S22 in order to climb the focus compensator 105 in the direction corresponding to the mounting change. On the other hand, if the mounting state has not changed, the normal restart monitoring process of step S34 is performed. That is, by checking whether or not the current AF evaluation value signal level fluctuates in comparison with the AF evaluation value signal level at the time of focus stored in step S32 (step S34), it is determined whether or not to restart. Is determined (step S35). For example, when the current AF evaluation value signal level fluctuates by a predetermined percentage or more with respect to the stored AF evaluation value signal level at the time of in-focus, it is assumed that the subject has changed due to panning or the like and “restart”. If the change is less than a predetermined percentage, it is determined that the subject has not changed and “do not restart”.
[0045]
If it is determined in step S35 that "do not restart", the focus compensator 105 is stopped as it is (step S36), the process returns to step S33, and restart monitoring is performed again. On the other hand, when it is determined that “restart”, the process is restarted by returning to step S21. By repeating such an operation, the movement of the focus lens 105 is controlled so that the in-focus state can be constantly maintained.
[0046]
As described above, according to the second embodiment, forcible hill climbing in the in-focus direction according to how the mounting state changes makes it possible to more quickly perform blurring that occurs when the mounting state changes. In particular, when the blurring occurs due to a change in the wearing state, the AF evaluation value is buried in the noise level even if the wobbling operation is performed. It is possible to prevent the time required to reach a long time.
[0047]
【The invention's effect】
As described above, according to the present invention, it is possible to quickly eliminate blurring that occurs when the mounting state of a lens that is attached to and detached from the optical axis of a wide attachment lens or the like and changes the focal length is changed. It becomes.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a video integrated camera to which an imaging apparatus according to an embodiment of the present invention is applied.
FIG. 2 is a flowchart showing a focus control operation in the first embodiment of the present invention.
FIG. 3 is a flowchart showing a focus control operation in the second embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of an inner focus type lens system equipped with a wide attachment lens unit.
FIG. 5 is a diagram illustrating a trajectory representing a relationship between a zoom lens position for each subject distance and a focus lens position for focusing in an inner focus type lens system.
6 is a diagram illustrating a locus corresponding to FIG. 5 when a wide attachment lens is attached. FIG.
[Explanation of symbols]
102 ... Variable power lens 105 ... Focus lens 106 ... Imaging device (CCD)
116: Frame generation circuit 115 ... AF microcomputer 117 ... AF evaluation value processing circuit 120 ... Driver (for focus lens)
121 ... Motor (for focus lens)
122 ... Wide attachment lens 123 ... Lens slide mechanism (for wide attachment lens)
124 ... Lens wearing detection switch (for wide attachment lens)

Claims (4)

A lens system capable of mounting a second lens group for changing the focal length on the same optical axis as the first lens group for performing focus adjustment;
A sharpness signal corresponding to the degree of focus is extracted from a video signal obtained by photoelectrically converting an optical subject image formed through the lens system, and the movement of the first lens group is controlled based on the sharpness signal. Focusing control means for performing focusing control by doing,
An imaging device comprising: restarting means for moving the first lens group and restarting focusing control by the focusing control means when the mounting state of the second lens group is changed. apparatus. The restarting means has detection means for detecting a change in the mounting state of the second lens group, and the first means when the change in the mounting state of the second lens group is detected by the detection means. imaging device to move the lens groups according to claim 1, wherein the restarting the focus control by the focus control means. When the mounting state of the second lens group is changed, the restarting unit moves the first lens group in a predetermined direction according to the changed state and performs focusing control by the focusing control unit. The imaging apparatus according to claim 1 , wherein the imaging apparatus is restarted. When the second lens group is changed from the attached state to the non-attached state, the restarting means is in the infinite direction, and when the second lens group is changed from the non-attached state to the attached state, the first lens group is in the closest direction. The image pickup apparatus according to claim 3, wherein the focus control by the focus control means is restarted by moving the camera.

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