JP2006343496A - Automatic focusing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing apparatus capable of restraining a pumping phenomenon even when minutely vibrating a focusing lens in an automatic focusing operation. <P>SOLUTION: The automatic focusing apparatus includes: the focusing lens 1; a variable lens 2 disposed on the imaging element 3 side of the focusing lens 1; and a control section 8 for minutely vibrating the focusing lens 1 for automatic focus control and also minutely vibrating the variable lens 2 so as to correspond to the minute vibration of the focusing lens 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an automatic focusing device for a camera, and more particularly to an automatic focusing device for a camera provided with a focusing lens and a zooming lens.

  In recent years, small cameras have become widespread centering on so-called digital cameras. In addition, sales of mobile phones equipped with digital cameras are on the rise, and this trend is spreading worldwide. Digital cameras mounted on mobile phones are being developed for higher pixel count and higher functionality. For example, in a digital camera mounted on a mobile phone, various functions such as a zoom function using an optical zoom lens, an autofocus function, and a camera shake prevention function have been developed in the same way as a digital movie.

  In particular, since a mobile phone is required to be portable, the mounted digital camera is required to be ultra-smaller than a digital movie. For example, the size of a digital camera lens mounted on a mobile phone is one or more orders of magnitude smaller than that of a digital movie lens.

  In general, there are two methods for focusing on a digital camera: manual focus, which is performed manually by visually observing the screen, and autofocus, which is performed automatically. However, an autofocus function is strongly required for digital cameras mounted on mobile phones. Yes. One of the reasons is that it is difficult to manually perform focusing because of the increase in the number of pixels. Another reason is that the screen size of the display device of the mobile phone is small. Further, since the display device of the mobile phone has a smaller number of pixels than the number of pixels of the camera, the image information obtained by photographing must be thinned and displayed, and the display is displayed on the display device with reduced resolution. Therefore, it is one of the reasons that it is extremely difficult to visually confirm the degree of focus. Furthermore, a digital camera mounted on a conventional mobile phone has a pan-focus function that does not require focusing. However, in recent years, a macro photographing function is required to read a two-dimensional barcode, and the photographing is performed. With the demand for an optical zoom function that expands the width of the camera, an autofocus function capable of high-precision focusing has been strongly demanded.

  As an implementation form of the autofocus function, there is an infrared autofocus. This method is used in home movies and the like, but requires a distance measuring device and is not suitable for use in a micro camera. In other implementations, the focus lens is momentarily microvibrated, and the degree of focus is determined based on the amount of change in the high frequency component in the video signal and the phase information corresponding to the vibration (hereinafter referred to as microvibration). (For example, refer to Patent Document 1). The micro-vibration method is a method adopted in many home movies and is not a special automatic focusing method. In addition, this method is suitable when an ultra-small camera is configured because a distance measuring device is not required.

FIG. 11 is a principal block diagram showing an automatic focusing device that employs a micro-vibration method disclosed in FIG. In FIG. 11, 101 is an objective lens, 102 is a zoom lens, 103 is a zoom encoder that outputs positional information of the zoom lens 102, 104 is an imaging lens (focus lens), 105 is an image sensor, and 106 is A signal processing circuit that converts a signal obtained from the image sensor 105 into a video signal, integrates and detects a high frequency component in the luminance signal of the video signal, and outputs a focus voltage, 107 extracts a predetermined fluctuation component of the focus voltage A fluctuation component extracting circuit 108 for controlling the focus lens 104, a zooming lens 102, and the like, and a controller for driving and controlling the zoom lens 102. Only Memory) 109 is a photo frame composed of a stepping motor or the like for driving the focusing lens 104. A focus motor 110 is a zoom motor composed of a DC motor or the like for driving the zoom lens 102.
FIG. 12 is an explanatory diagram showing the relationship between the focus lens position and the focus voltage and the fluctuation component of the focus voltage in the micro-vibration method, and is a diagram disclosed in Patent Document 1 as FIG. The micro-vibration method uses a high-frequency component in the video signal, but the characteristic curve of the high-frequency component becomes maximum at the focal point as shown in FIG. 12B, and decreases as the focus is lost. It has the shape of

  Therefore, in the auto focus control in the minute vibration method, first, the focus lens 104 is minutely vibrated at an early cycle, thereby slightly changing the focus with respect to the subject to cause a minute change in the high frequency component in the video signal. . When the focus lens 104 is vibrated minutely, the characteristic curve of the high frequency component has a mountain shape, so the slope of the mountain is opposite depending on which side of the mountain the focus lens 104 is located, The phase of the minute change of the high frequency component with respect to the vibration phase of the focusing lens 104 is reversed. Therefore, by comparing the vibration phase of the focus lens 104 and the phase of the high frequency component in the video signal, the in-focus direction can be detected, so that the auto focus can be achieved by moving the focus lens 104 while vibrating in that direction. The operation can be performed.

  In autofocus control, the mountain climbs toward the summit, which is the focal point, in this way, but the slope of the mountain is smaller near the summit, so the minute change amplitude of the high-frequency component is smaller, and the amplitude is almost 0 is the minimum. In such a state, it is determined that the in-focus point has been reached, and if the movement of the lens is stopped, the autofocus control operation is completed. If it is determined that the subject has changed due to a change in the high-frequency component after the stop, the focus lens 104 is again vibrated slightly and the autofocus operation as described above is started. A focusing device can be configured.

  Incidentally, as shown in FIG. 11, the automatic focusing device disclosed in Patent Document 1 employs a so-called rear-lens focus method in which a focusing lens 104 is disposed on the imaging element 105 side of the zoom lens 102. ing.

  In the rear lens focus method, a zoom system is configured by the objective lens 101 which is the front lens and the zoom lens 102, and the zoom magnification is changed by changing the distance between the objective lens 101 and the zoom lens 102. Further, the focusing lens 104 which is the rear lens closest to the image sensor 105 is used for focusing, and the focusing lens 104 is moved back and forth to perform focusing. In such an optical system, the parallel light beam incident on the zoom system is incident on the focusing lens 104 in a form almost similar to the parallel light beam after changing the magnification, and forms an image there. Therefore, even if the focusing lens 104 is slightly vibrated back and forth for focusing, the focal length of the entire zoom lens hardly changes and the angle of view hardly changes. Therefore, even if an autofocus operation by minute vibration is performed using such a variable power lens, the angle of view, that is, the pumping phenomenon due to minute vibration hardly occurs on the captured image.

  However, this rear-lens focus method is a three-group configuration of an objective lens, a variable power lens, and a focus lens, so that it is difficult to reduce the size, and the digital camera mounted on the mobile phone should be ultra-miniaturized. In many cases, a so-called two-lens front lens focus method is employed in which a zoom lens is disposed on the imaging element side of the focus lens.

JP-A-6-169423

JP-A-10-282396

  FIG. 13 is an explanatory diagram illustrating a lens configuration and a lens characteristic curve of an automatic focusing device that employs the front lens focus method. As shown in FIG. 13A, the automatic focusing device has a so-called two-group configuration in which a focusing lens 104 is disposed on the subject side and a zoom lens 102 is disposed on the imaging element 105 side. It is a zoom lens. In the following description, between the subject and the image sensor, the subject side is the front side, and the image sensor side is the rear side.

  Focusing can be performed by moving the focusing lens 104 that is the first group back and forth, and zoom magnification can be changed by moving the zooming lens 102 that is the second group back and forth. it can.

  FIG. 13B is a lens characteristic curve when the lens configuration shown in FIG. In FIG. 13B, FL1 and FL2 indicate characteristic curves of the focusing lens 101, and ZL indicates a characteristic curve of the zoom lens 102. In a two-group zoom lens, when the zoom lens 102 is moved back and forth to change the zoom magnification, the combined focal length determined by the focus lens 104 and the zoom lens 102 changes, The zoom ratio changes between wide. However, in such a two-group lens, if the distance between the first group and the second group is simply changed, the imaging position where the image is formed before the distance is changed moves due to the change in the lens arrangement. Will result in blurring. For this reason, in such a two-group lens, it is necessary to move the zoom lens 102 to change the focal length, and at the same time to change the position of the focus lens 104 to prevent a focus shift. The change characteristic of the lens position when the zoom magnification is changed while preventing such defocusing is a characteristic curve shown in FIG. 13B, a so-called zoom trace curve. For example, when the zoom lens 102 is moved and the zoom magnification is changed while the subject at the ∞ position is being photographed, the focus lens 104 is moved according to the characteristic curve FL2, as shown in FIG. 13B. Therefore, it is necessary to maintain the focus during the zoom operation. Similarly, when photographing a subject at a macro position, it is necessary to maintain the focus during the zoom operation by moving the focusing lens 101 according to the characteristic curve FL1.

  As described above, the trace curve has been described based on the movement of the zoom lens 102. However, even if the focus lens 104 is moved for focusing, the focus lens 104 and the zoom lens 102 are not moved. The distance between changes. Therefore, since the combined focal length changes with this change, the zoom magnification changes, and when the focus lens is vibrated minutely in order to perform autofocus control, minute fluctuations in the angle of view occur. This minute change in the angle of view appears as a minute pumping phenomenon.

  Although the period of minute vibration varies depending on the image generation period of the video signal of the camera, it is necessary to detect blurring of the screen by associating one screen with the antinode of vibration in the minute vibration of the lens. It is necessary to set it to half or less of the frequency of the generation cycle. If this period is lengthened, the tracking performance of autofocus deteriorates, so a frequency such as 1/4 is often used. For example, in the NTSC system, the frequency is 15 Hz, but if the angle of view changes in this cycle, the quality of the captured image is significantly impaired. It also gives discomfort to those who are watching the monitor screen. Therefore, it is necessary to suppress such a minute and frequent pumping phenomenon.

  Next, a difference in appearance on the screen between a minute pumping phenomenon that occurs in the autofocus operation when the front lens focus method is employed and a minute blur change necessary for the autofocus operation will be described.

  In the rear-lens focus method as shown in Patent Document 1, the change in the captured image of the subject that occurs along with the autofocus control and is recognized by the photographer is only the change in the focus, and the change in the angle of view is Almost does not occur. In general, even if a slight blur occurs in a subject, if the blur is minute, it is difficult to recognize on a captured image. For example, when focusing, the focus lens is moved before and after the best focus position, and the focus lens is stopped at the center position of the forward and backward movement that is determined to be the position where the blur is minimized. This is because it is difficult to observe and detect minute blur as an absolute value, so moving the focus lens before and after the best focus position generates large blur and confirms the focus condition. This is because it is necessary to stop the lens at the center of the back-and-forth movement which seems to be the best focus position.

  On the other hand, since the size of the subject itself changes, the pumping phenomenon is observed and detected by the photographer even if a slight change occurs. This is obvious if a change in the edge portion of the subject is assumed. That is, when the focus is deviated, the contour of the edge portion changes so as to blur, but when the angle of view changes, the edge portion moves. Accordingly, since the shape of the image changes due to the pumping phenomenon, it is easier to detect than a minute focus change that does not change the shape of the entire image and slightly blurs. For this reason, the minute and frequent pumping phenomenon greatly impairs the appearance of the subject image during the autofocus operation, and unless this phenomenon is suppressed, the minute vibration method cannot be applied to the front lens focus method. Have difficulty.

  On the other hand, a countermeasure for the pumping phenomenon itself has been studied in TV broadcast cameras that often employ the front lens focus method. As an example of countermeasures, there has been proposed a method of calculating a zoom position that cancels out the angle of view variation caused by the focusing lens and changing the zoom ratio according to the calculation result (for example, Patent Document 2).

  In the TV broadcast camera disclosed in Patent Document 2, the focus lens does not move fast because the cameraman performs a focusing operation. Therefore, the amount of movement of the focus lens is detected, and pumping is performed according to the detected amount of movement. It was possible to calculate a zoom magnification that suppresses the phenomenon and to change to the calculated zoom magnification.

  However, since the pumping phenomenon targeted by the correction control disclosed in Patent Document 2 is caused by lens movement based on a manual focus operation by a cameraman, consideration is given to the high-speed response of the correction control itself. It has not been. In order to suppress the pumping phenomenon caused by frequent minute vibrations with a short vibration cycle, which is the subject of the present invention, using the suppression method applied to the TV broadcast camera disclosed in Patent Document 2, a correction amount from detection is used. Since a high-speed operation of a series of operations from calculation to correction control is required, a highly responsive detection system or the like is required, resulting in a high cost. Further, the TV broadcast camera disclosed in Patent Document 2 has a large shape due to the fact that the zoom lens itself pursues high optical performance, and the auto focus control by micro vibrations is originally performed. Therefore, there was no need to consider the problem of suppression of the pumping phenomenon due to minute vibrations.

  The problem to be solved by the present invention is a problem that occurs for the first time because the zoom lens itself is miniaturized, and it is not difficult to vibrate the focus lens that is the front lens. Documents 1 and 2 do not describe any suppression of the pumping phenomenon from such a viewpoint.

  The present invention has been made to solve such a problem. In the so-called front lens focus method, an automatic focusing device capable of suppressing the occurrence of a pumping phenomenon even when a focus lens is vibrated minutely by an autofocus operation. The purpose is to provide.

  An automatic focusing device according to the present invention includes a focusing lens, a zoom lens provided on the imaging element side of the focusing lens, and a micro-vibration of the focusing lens for autofocus control. And a control means for minutely vibrating the zoom lens in response to the minute vibration of the focus lens. With such a configuration, the occurrence of a pumping phenomenon can be suppressed.

  Here, in the case where the focusing lens is moved to the in-focus position by autofocus control, the control unit may execute control for moving the zooming lens in response to the movement of the focusing lens. preferable. Such control can more reliably suppress the occurrence of the pumping phenomenon.

  Further, the control means may execute control for minutely vibrating the zoom lens so that a distance between the focus lens and the zoom lens is substantially constant.

  Furthermore, it is preferable that the control means executes control for moving the focusing lens in accordance with the movement of the zooming lens when the zooming lens is moved for optical zooming by an operator. .

  An automatic focusing device according to the present invention is an electronic device that performs electronic zoom based on a focusing lens, a zoom lens provided on the imaging element side of the focusing lens, and a video signal output from the imaging element. The zoom means and a control means for minutely vibrating the focus lens for autofocus control, the electronic zoom means varies the electronic zoom magnification in response to the minute vibration of the focus lens. .

  Further, it is preferable that the control unit executes control for moving the zoom lens in response to the movement of the focus lens when the focus lens is moved to a focus position by auto focus control. .

  Further, the control means may execute control for moving the focus lens position in accordance with the movement of the zoom lens when the zoom lens is moved by an operator for optical zoom. preferable.

  The lens driving method according to the present invention is a driving method of a focusing lens and a zoom lens provided on the imaging element side of the focusing lens, and the focusing lens is minutely used for autofocus control. A step of vibrating, and a step of minutely vibrating the zooming lens in response to the minute vibration of the focusing lens.

  A lens driving method according to another aspect of the present invention is a driving method of a focusing lens and a zooming lens provided on the imaging element side of the focusing lens, and the focus driving for autofocus control. And a step of varying the electronic zoom magnification in response to the minute vibration of the focusing lens.

  According to the present invention, it is possible to provide an automatic focusing device that can suppress the occurrence of a pumping phenomenon even when the focus lens is vibrated minutely by an autofocus operation in a so-called front lens focus method.

Embodiment 1 of the Invention
FIG. 1 is a block diagram illustrating a configuration example of the automatic focusing apparatus according to the first embodiment. This automatic focusing device can capture not only still images but also moving images. As shown in the figure, the automatic focusing device includes a focusing lens 1, a zooming lens 2, an image sensor 3, an image processing unit 4, an image output terminal 5, a focusing lens driving unit 6, and a zooming lens. A drive unit 7 and a control unit 8 are provided.

  The focusing lens 1 is a so-called imaging lens for focusing. The zoom lens 2 is a zoom lens for changing the zoom magnification. The zoom lens 2 is provided on the rear side of the focus lens 1 and employs a so-called front lens focus system. The focusing lens 1 and the zooming lens 2 may each be a single lens configuration or a plurality of lenses.

  An imaging device 3 is provided on the exit side of the zoom lens 2. The image pickup device 3 is configured by a CCD (Charge Coupled Device) or the like, and generates a video signal according to incident light incident through the focus lens 1 and the zoom lens 2. The video signal output from the image sensor 3 is input to the image processing unit 4 and various image processing is executed. The video signal processed by the image processing unit 4 is output from the terminal 5 and input to the control unit 8. The image processing unit 4 integrates and detects the high frequency component in the luminance signal of the video signal, generates a focus voltage having a characteristic that takes a maximum value at the focal point, and outputs the focus voltage value to the control unit 8. In addition, the image processing unit 4 extracts the fluctuation component phase of the focus voltage and outputs the extraction result to the control unit 8. Specific processing of the image processing unit 4 for realizing the autofocus function is disclosed in, for example, Patent Document 1. The image processing unit 4 may have an electronic zoom function.

  The focus lens driving unit 6 is an actuator for driving the focus lens 1 in accordance with a control signal output from the control unit 8 and controlling the position of the focus lens 1. The zoom lens driving unit 7 is an actuator for driving the zoom lens 2 in accordance with a control signal output from the control unit 8 and controlling the position of the zoom lens 2. The focus lens driving unit 6 and the zoom lens driving unit 7 are configured by, for example, a step motor.

  The control unit 8 is composed of, for example, a microcomputer, determines whether or not the focusing lens 1 is in focus based on the amplitude value of the focus voltage output from the image processing unit 4, and focuses based on the fluctuation component phase. It is determined whether the focusing lens 1 needs to be moved forward or backward in order to adjust the movement, that is, the moving direction. The control unit 8 includes a focus lens position calculation unit 81 and a zoom lens position calculation unit 82. The focus lens position calculation unit 81 causes the focus lens 1 to vibrate slightly based on the determination result of whether or not the focus lens 1 is in focus and the determination result related to the moving direction, and performs autofocus. The position of the working lens 1 is calculated. The calculation of the position of the focus lens 1 by the focus lens position calculation unit 81 is executed based on a predetermined algorithm. The focus lens position calculation unit 81 calculates the position of the focus lens 1, thereby calculating the amplitude of minute vibrations of the focus lens 1. Specifically, for example, the position of the focusing lens can be calculated by the calculation method disclosed in Patent Document 1, but a detailed description is omitted because a known technique can be used.

  The zoom lens position calculation unit 82 calculates the position of the zoom lens 2 such that the angle of view is substantially constant based on the focus lens position information calculated by the focus lens position calculation unit 81. For example, a storage unit (not shown) correlates the position of the focusing lens and the position of the zooming lens 2 that makes the angle of view substantially constant when the focusing lens 1 is disposed at the focusing lens position. Stored in advance. The zoom lens position calculation unit 82 acquires focus lens position information (including movement information of the focus lens position) from the focus lens position calculation unit 81, refers to the storage unit, and acquires the acquired focus lens position information. The position of the zoom lens 2 is calculated by acquiring the zoom lens position information associated with the lens position.

  In the control method disclosed in Patent Document 2, it is necessary to detect the amount of movement of the focusing lens 1 that is manually operated to determine the position of the zoom lens 2. Since the control unit 8 is only required to have a position determined so that the angle of view becomes substantially constant corresponding to the position of the focus lens 1, the zoom lens according to the minute vibration of the focus lens 1. The position of 2 can be easily calculated.

  The control unit 8 controls the focus lens driving unit 6 and the zoom lens driving unit 7 in accordance with the calculation results by the focus lens position calculation unit 81 and the zoom lens position calculation unit 82.

  FIG. 2 is an explanatory diagram illustrating a lens driving method according to the first embodiment. In the figure, the vertical axis represents time (T), and the horizontal axis represents lens position (P). In FIG. 2, Wf represents the amplitude of the minute vibration, Pf represents the locus of the lens position of the focusing lens, and Cf represents the vibration center of the focusing lens. Further, Wz represents the amplitude of the zoom lens, Pz represents the locus of the lens position of the zoom lens, and Cz represents the vibration center of the zoom lens.

  As shown in the locus Pf of FIG. 2, the focus lens 1 has the vibration center Cf at the same position, but slightly vibrates with the amplitude Wf around the vibration center Cf. In the temporal range shown in FIG. 2, the focusing lens 1 vibrates about four times (that is, about four reciprocations) at the same position, but it is sufficient that there is at least one reciprocation. Perform 4 or 5 round trips. In this way, the focus lens 1 can be finely oscillated to smoothly follow the focal point and suppress defocusing. The amplitude for microvibration varies depending on the lens diameter, focal length, etc., but is, for example, about 5 to 10 μm.

  In this way, when the focus lens 1 is vibrated minutely, if the position of the zoom lens 2 is not adjusted, the distance between the focus lens 1 and the zoom lens 2 changes minutely. As the overall composite focal length changes, the pumping phenomenon becomes significant. In the first embodiment, the zoom lens position is also controlled so as to suppress the occurrence of the pumping phenomenon.

  Specifically, as shown in the locus Pz of the zoom lens 2 shown in FIG. 2, the zoom is synchronized with the minute vibration of the lens position of the focus lens 1 (that is, with substantially the same phase). The lens 2 is also vibrated minutely. That is, at the timing when the focusing lens 1 is moved forward, the zooming lens 2 is also moved forward, and at the timing when the focusing lens 1 is moved backward, the zooming lens 2 is also moved backward. The movement period is substantially the same.

  In this example, the amplitude Wz of the zoom lens 2 has the same amplitude as the focus lens amplitude Wf. Further, the vibration center Cz of the zoom lens 2 is at the same position as the vibration center Cz of the focus lens 1. That is, the vibration center Cz of the zoom lens 2 is not moved in the time range shown in FIG.

  In a preferred embodiment, when the focusing lens 1 is slightly vibrated, the zooming lens 2 is slightly vibrated so that the relative positions of the focusing lens 1 and the zooming lens 2 are substantially constant. Yes. That is, the zoom lens 2 is vibrated slightly so that the distance between the zoom lens 2 and the focus lens 1 is substantially constant. Thereby, a view angle fluctuation | variation can be suppressed.

  As described above, in the automatic focusing apparatus according to the first embodiment, the focusing lens 1 is caused to vibrate minutely, and the minute vibration corresponding to the minute vibration of the focusing lens 1 is applied to the zoom lens 2. The pumping phenomenon can be suppressed because it is also executed.

  The amplitude of the focus lens 1 and the amplitude of the zoom lens 2 are preferably the same. For example, when each lens is driven by a step motor, the movement amount per step is as follows. When the step motor for driving the focusing lens 1 and the step motor for driving the zoom lens 2 are different, it is preferable to control the same amplitude as much as possible. Any differences are within the scope of the present invention.

  In addition, when the F value of the lens changes due to vignetting or the like in the lens as the zoom lens 2 moves, in order to keep the change in the size of defocus due to minute vibration constant, the F value The minute vibration amount may be changed in accordance with the change of.

Embodiment 2 of the Invention
In the lens driving method according to the first embodiment of the invention described with reference to FIG. 2, the vibration center is constant, but in the second embodiment, the lens driving method when the vibration center is moved is used. Will be described. The configuration of the automatic focusing device according to the second embodiment is the same as that of the automatic focusing device according to the first embodiment of the invention shown in FIG.

  FIG. 3 is an explanatory diagram illustrating a lens driving method according to the second embodiment. As shown in the figure, the vibration center Cf of the focusing lens 1 moves from Cf1 to Cf2. By moving the focus lens 1 while vibrating in this way, the direction of focus is detected based on the amplitude and phase of the vibration component included in the high frequency component in the video signal obtained by the minute vibration. The autofocus operation can be realized by determining the focus.

  In the second embodiment, the focusing lens 1 is microvibrated and the center of vibration is moved, whereas the zoom lens 2 performs microvibration corresponding to the focusing lens 1. The vibration center is constant without being moved.

  Therefore, when the vibration center of the focusing lens 1 is at Cf1 and when it is at Cf2, the distance between the lenses with the zooming lens 2 changes, and the focal length of the entire lens changes. Since this change does not appear as a steep pumping phenomenon due to minute vibrations, there are few problems.

Embodiment 3 of the Invention
In the lens driving method according to the second embodiment of the invention described with reference to FIG. 3, even when the vibration center of the focus lens 1 is moved, the vibration center of the zoom lens 2 is constant. However, in the third embodiment, the vibration center of the zoom lens 2 is also moved according to the movement of the vibration center of the focus lens 1. The configuration of the automatic focusing apparatus according to the third embodiment is the same as that of the automatic focusing apparatus according to the first embodiment of the invention shown in FIG.

  FIG. 4 is an explanatory diagram illustrating a lens driving method according to the third embodiment. As shown in the figure, the vibration center Cf of the focusing lens 1 moves from Cf1 to Cf2. By moving the focus lens 1 while vibrating in this way, the direction of focus is detected based on the amplitude and phase of the vibration component included in the high frequency component in the video signal obtained by the minute vibration. The autofocus operation can be realized by determining the focus.

  In the third embodiment, the zoom lens 2 performs minute vibration corresponding to the focus lens 1 and the vibration center Cz also moves in synchronization with the focus lens 1 from Cz1 to Cz2. In this example, the movement amount of the vibration center of the focusing lens 1 and the movement amount of the vibration center of the zoom lens 2 are substantially the same.

  Therefore, when the vibration center of the focus lens 1 is at Cf1 and when it is at Cf2, the distance between the lens and the zoom lens 2 is substantially constant, and the focal length of the entire lens is constant. The phenomenon can be reliably suppressed.

Embodiment 4 of the Invention
The automatic focusing apparatus according to the fourth embodiment includes a correcting unit for correcting the driving state when the driving mechanisms in the focusing lens driving unit 6 and the zooming lens driving unit 7 are not the same. For example, when a step motor is used for each of the focus lens drive unit 6 and the zoom lens drive unit 7, the amount of movement per step differs between the two.

  FIG. 5 is a block diagram showing a configuration of the automatic focusing device. As shown in the figure, the automatic focusing apparatus further includes a pumping correction amount calculation unit 83 in the control unit 8. Other configurations are the same as those of the automatic focusing device shown in FIG. 1, but the focus lens driving unit 6 and the zoom lens driving unit 7 in this example have different driving mechanisms.

  The pumping correction amount calculation unit 83 sets a correction amount such that the zoom lens 2 has substantially the same movement amount with respect to the movement of the focus lens 1 to the vibration center of the minute vibration, and the movement amount can suppress the pumping phenomenon. calculate. That is, the pumping correction amount calculation unit 83 calculates a correction amount for canceling the difference in driving mechanism between the focus lens driving unit 6 and the zoom lens driving unit 7.

  In addition, the pumping correction amount calculation unit 83 may prepare and calculate correction amounts corresponding to different lens configurations in advance. Also in this case, a correction amount that suppresses the pumping phenomenon is calculated.

Embodiment 5 of the Invention
In the automatic focusing device according to the fifth embodiment, control for changing the electronic zoom magnification is performed in order to suppress the pumping phenomenon.

  FIG. 6 is a block diagram illustrating a configuration of an automatic focusing apparatus according to the fifth embodiment. As shown in the figure, the basic configuration is the same as the automatic focusing device shown in FIG. 1, but the automatic focusing device according to the present embodiment includes an electronic zoom correction unit 41 in the image processing unit 4. On the other hand, the control unit 8 is different in that it does not include a zoom lens position calculation unit.

  The electronic zoom correction unit 41 has a function of correcting the electronic zoom magnification according to the minute vibration of the focusing lens 1. The zoom lens 2 does not perform a moving operation for suppressing the pumping phenomenon caused by the minute vibration of the focus lens 1.

  FIG. 7 is an explanatory diagram illustrating lens movement and electronic zoom magnification change according to the fifth embodiment. As shown in the figure, the focusing lens 1 vibrates slightly, and the vibration center Cf also moves from the vibration centers Cf1 to Cf2. On the other hand, the position Pz of the zoom lens 2 is constant and has not moved.

  Regarding the electronic zoom magnification, the magnification Pd is varied so as to suppress the variation in the angle of view caused by the minute vibration of the focusing lens 1. The magnification variation is synchronized with the minute vibration of the focusing lens 1 and the phase is substantially the same. Further, the fluctuation cycle of the magnification fluctuation is substantially the same as the minute vibration of the focusing lens 1. The variation range of the magnification is determined in advance according to the amount of field angle variation caused by the minute vibration of the focusing lens 1. That is, the electronic zoom correction unit 41 changes the electronic zoom magnification according to the minute vibration of the focusing lens 1 so as to suppress the view angle variation caused by the minute vibration. In this example, even if the vibration center of the focusing lens 1 moves, the electronic zoom correction unit 41 does not change the electronic zoom magnification according to the movement.

  As described above, in the present embodiment, the pumping phenomenon is suppressed by changing the magnification of the electron beam, so that it is necessary for minute vibration control as compared with the case where the zoom lens 2 is slightly changed. There is an effect that power consumption can be suppressed.

  In determining the change in the magnification of the electronic zoom, it is desirable to set with reference to the position of the zoom lens 2 as well as the position of the focus lens 1. The occurrence of the pumping phenomenon depends on the combined focal length of the focusing lens 1 and the zooming lens 2, so even if the same minute vibration amount is given to the focusing lens 1, it depends on the position of the zooming lens 2. This is because the angle of view variation is different.

Embodiment 6 of the Invention
In the automatic focusing device according to the sixth embodiment, not only the electronic zoom magnification is changed according to the minute vibration of the focus lens 1 but also the magnification lens 2 according to the movement of the vibration center of the focus lens 1. Is moving.

  FIG. 8 is an explanatory diagram illustrating lens movement and electronic zoom magnification change according to the sixth embodiment. As shown in the figure, the focusing lens 1 vibrates slightly, and the vibration center Cf also moves from the vibration centers Cf1 to Cf2.

  The position Pz of the zoom lens 2 is moved according to the movement of the vibration center of the focus lens 1. Specifically, the zoom lens 2 moves so that the distance from the focus lens 1 is substantially constant. Thereby, the pumping phenomenon generated by the movement of the vibration center of the focusing lens 1 can be suppressed.

  Regarding the electronic zoom magnification, the magnification Pd is varied so as to suppress the variation in the angle of view caused by the minute vibration of the focusing lens 1. The magnification variation is synchronized with the minute vibration of the focusing lens 1 and the phase is substantially the same. Further, the fluctuation cycle of the magnification fluctuation is substantially the same as the minute vibration of the focusing lens 1. The variation range of the magnification is determined in advance according to the amount of field angle variation caused by the minute vibration of the focusing lens 1. That is, the electronic zoom correction unit 41 changes the electronic zoom magnification according to the minute vibration of the focusing lens 1 so as to suppress the view angle variation caused by the minute vibration. Thereby, the pumping phenomenon generated by the minute vibration of the focusing lens 1 can be suppressed. In this example, the electronic zoom correction unit 41 does not change the electronic zoom magnification according to the movement of the vibration center of the focusing lens 1.

  In the present embodiment, the zoom lens 2 is moved according to the movement of the vibration center of the focus lens 1, but is not moved according to the minute vibration of the focus lens 1. There is an effect that power consumption can be suppressed as compared with the case where the lens 2 is vibrated minutely.

Embodiment 7 of the Invention
The present embodiment relates to a driving method of each lens when the operator moves the zoom lens 2 to perform optical zoom. FIG. 9 is an explanatory diagram showing the movement of the lens according to the seventh embodiment. As shown in the drawing, the operator moves the vibration center of the zoom lens 2 to Cz1, Cz2, Cz3, Cz4, and Cz5 in order to perform optical zoom. As described above, when the zooming lens 2 is moved, the image forming position also changes with the focal length. Therefore, it is necessary to move the focusing lens 1 according to the characteristic curves FL1 and FL2 as shown in FIG. is there. In this example, the vibration center of the focusing lens 1 is moved to Cf1, Cf2, and Cf3.

  Further, in the present embodiment, since the focusing lens 1 is minutely oscillated for autofocusing, the zooming lens 2 is minutely synchronized with this in order to suppress the pumping phenomenon caused by the minute vibration. It is vibrating.

  According to the automatic focusing apparatus according to the present embodiment, it is possible to suppress a pumping phenomenon that occurs due to minute vibrations of the focusing lens 1 even when an optical zoom operation is performed.

Embodiment 8 of the Invention
This embodiment relates to a case where the zoom lens 2 is moved by the operator to perform optical zoom. FIG. 10 is an explanatory diagram illustrating lens movement and electronic zoom magnification change according to the eighth embodiment. As shown in the figure, the operator moves the zoom lens 2 to Pz1, Pz2, Pz3, Pz4, and Pz5 in order to perform optical zoom. As described above, when the zooming lens 2 is moved, the image forming position also changes with the focal length. Therefore, it is necessary to move the focusing lens 1 according to the characteristic curves FL1 and FL2 as shown in FIG. is there. In this example, the vibration center of the focusing lens 1 is moved to Cf1, Cf2, and Cf3.

  Further, in the present embodiment, since the focusing lens 1 is finely oscillated for autofocusing, the electronic zoom magnification is also changed in synchronism with this in order to suppress the pumping phenomenon generated by the microvibration. Yes.

  According to the automatic focusing apparatus according to the present embodiment, it is possible to suppress a pumping phenomenon that occurs due to minute vibrations of the focusing lens 1 even when an optical zoom operation is performed. In particular, in this embodiment, it is not necessary to minutely vibrate the zoom lens 2, so that power consumption can be reduced.

It is a block diagram which shows the structure of the automatic focusing apparatus concerning this invention. It is explanatory drawing which shows the drive method of each lens concerning this invention. It is explanatory drawing which shows the drive method of each lens concerning this invention. It is explanatory drawing which shows the drive method of each lens concerning this invention. It is a block diagram which shows the structure of the automatic focusing apparatus concerning this invention. It is a block diagram which shows the structure of the automatic focusing apparatus concerning this invention. It is explanatory drawing which shows the drive method of each lens concerning this invention, and the change of an electronic zoom magnification. It is explanatory drawing which shows the drive method of each lens concerning this invention, and the change of an electronic zoom magnification. It is explanatory drawing which shows the drive method of each lens concerning this invention. It is explanatory drawing which shows the drive method of each lens concerning this invention, and the change of an electronic zoom magnification. It is a principal part block diagram which shows the automatic focusing apparatus which employ | adopted the conventional micro vibration system. It is explanatory drawing which showed the relationship between the lens position for a focus, and a focus voltage in the conventional automatic focusing apparatus, and the fluctuation component of a focus voltage. It is a conventional lens configuration and waveform diagram.

Explanation of symbols

1 focus lens, 2 zoom lens, 3 image sensor,
4 image processing unit, 5 image output terminal, 6 focus lens driving unit,
7 lens drive unit for zooming, 8 control unit, 81 lens position calculation unit for focus,
82 Lens position calculation unit for zooming, 83 Pumping correction amount calculation unit

Claims (9)

A focusing lens;
A zoom lens provided on the imaging element side of the focusing lens;
An automatic focusing apparatus comprising: a control unit that finely vibrates the focusing lens for autofocus control and finely vibrates the zoom lens in response to the minute vibration of the focusing lens.   The control means executes control for moving the zoom lens in response to the movement of the focus lens when the focus lens is moved to a focus position by autofocus control. The automatic focusing device according to claim 1.   2. The control unit according to claim 1, wherein the control unit executes a control for minutely vibrating the zoom lens so that a distance between the focus lens and the zoom lens is substantially constant. Automatic focusing device.   The control means executes control for moving the focus lens in accordance with the movement of the zoom lens when the zoom lens is moved by an operator for optical zoom. The automatic focusing device according to claim 1. A focusing lens;
A zoom lens provided on the imaging element side of the focusing lens;
Electronic zoom means for performing electronic zoom based on the video signal output from the image sensor;
Control means for minutely vibrating the focusing lens for autofocus control,
The electronic zoom means is an automatic focusing device that varies the electronic zoom magnification in response to minute vibrations of the focusing lens.   The control means executes control for moving the zoom lens in response to the movement of the focus lens when the focus lens is moved to a focus position by autofocus control. The automatic focusing device according to claim 4.   The control means executes control for moving the focus lens position in accordance with the movement of the zoom lens when the zoom lens is moved for optical zoom by an operator. The automatic focusing device according to claim 5 or 6. A driving method of a focusing lens and a zoom lens provided on the imaging element side of the focusing lens,
Micro-vibrating the focusing lens for autofocus control;
And a step of micro-vibrating the zoom lens corresponding to the micro-vibration of the focusing lens. A driving method of a focusing lens and a zoom lens provided on the imaging element side of the focusing lens,
Micro-vibrating the focusing lens for autofocus control;
And a step of changing the electronic zoom magnification in response to the minute vibration of the focusing lens.

Images