JP2004258208A - Automatic focusing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing device capable of performing a highly precise focusing. <P>SOLUTION: An AF microcomputer 713 performs control to determine and hold the position where the focus voltage during moving of a focus compensation lens 705 to one direction is maximized, to determine the focusing position from the position of the lens 705 where the focus voltage during the movement to a plurality of the one directions is maximized and to stop the lens 705 in the determined focusing position after passing the vertex of the focus voltage back and forth a prescribed number of times. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automatic focusing device used for an imaging device such as various video cameras.
[0002]
[Prior art]
In today's video camera automatic focusing devices (autofocus devices), the sharpness of the screen is detected from video signals obtained by subjecting a subject image to photoelectric conversion by an image sensor or the like, and AF (autofocus) evaluation is performed. The mainstream is a method in which the focus lens position is controlled so that the value becomes maximum, and the focus is adjusted.
[0003]
As the AF evaluation value, a level of a high-frequency component of a video signal generally extracted by a band-pass filter of a certain band is used. When a normal subject image is photographed, the value increases as the focus becomes higher as shown in FIG. 6, and the point at which the level becomes maximum is the focusing lens position.
[0004]
FIG. 7 is a block diagram showing a configuration of a video camera which is a conventional image pickup apparatus provided with an automatic focusing device. In FIG. 7, reference numeral 701 denotes a fixed first group lens, and 702 denotes a variable power lens for performing variable power. Reference numeral 703 denotes an aperture, reference numeral 704 denotes a fixed second group lens, and reference numeral 705 denotes a focus compensating lens (hereinafter referred to as a focus lens), which has both a function of correcting movement of a focal plane due to zooming and a function of focusing. Reference numeral 706 denotes a CCD as an image sensor, and 707 denotes a CDS / AGC, which samples the output of the CCD 706 and adjusts the gain. Reference numeral 708 denotes a camera signal processing circuit which processes an output signal from the CDS / AGC 707 into a signal corresponding to a recording device 709 described later. A recording device 709 uses a magnetic tape.
[0005]
Reference numeral 710 denotes a focus competition lens motor, which is an actuator for moving the focus lens 705. Reference numeral 711 denotes a focus competition lens driver which drives a motor 710 by a signal from an AF microcomputer 713 described later. Reference numeral 712 denotes an AF evaluation value processing circuit which extracts a high frequency component used for focus detection from an output signal of the CDS / AGC 707. An AF microcomputer 713 controls the driver 710 based on the output signal of the AF evaluation value processing circuit 712 and drives the focus lens 705, and has a position memory 714. A monitor device 715 displays an output signal of the camera signal processing circuit 708 and is used for monitoring a shooting scene.
[0006]
In the automatic focusing apparatus for a video camera configured as shown in FIG. 7, the AF microcomputer 713 moves the focus lens 705 so that the output signal level of the AF evaluation value processing circuit 712 is maximized in order to focus a normal image. Then, automatic focus adjustment is performed.
[0007]
Next, the AF control performed by the AF microcomputer 713 will be described with reference to FIGS.
[0008]
First, an AF (auto focus) processing operation will be described with reference to FIG.
[0009]
FIG. 8 is a flowchart showing a flow of the AF processing operation in the automatic focusing apparatus of the video camera shown in FIG.
[0010]
In FIG. 8, in step S801, a minute driving operation of the focus lens 705 is performed, and in the next step S802, it is determined whether or not the in-focus determination has been made. If it is determined that the focus determination cannot be performed, the process proceeds to step S803. If it is determined that the focus determination can be performed, the process proceeds to step S808.
[0011]
In step S803, it is determined whether the moving direction of the focus lens 705 has been determined. If it is determined that the moving direction of the focus lens 705 has been determined, the process proceeds to step S804. If it is determined that the moving direction of the focus lens 705 cannot be determined, the process returns to step S801.
[0012]
In step S804, after the focus lens 705 is driven to climb the hill at a high speed in the direction in which the AF evaluation value increases, the process proceeds to the next step S805. In step S805, it is determined whether the AF evaluation value has exceeded a peak. If it is determined that the AF evaluation value does not exceed the peak, the process returns to step S804. If it is determined that the AF evaluation value exceeds the peak, the process proceeds to step S806. Then, the focus lens 705 is returned to the focus lens position where the AF evaluation value is at the peak.
[0013]
Next, in step S807, it is determined whether the focus lens 705 has returned to the peak focus lens position in step S806. When it is determined that the focus lens 705 does not return to the peak focus lens position, the process proceeds to step S806. When it is determined that the focus lens 705 returns to the peak focus lens position, the process proceeds to step S801. Return.
[0014]
On the other hand, in step S808, the AF evaluation value level at the focal point is stored in the memory, and in the next step S809, the latest AF evaluation value is fetched. Next, in step S810, the AF evaluation value stored in step S808 is compared with the latest AF evaluation value acquired in step S809 to determine whether the fluctuation of the AF evaluation value is large. If it is determined that the AF evaluation value has fluctuated significantly, the process returns to step S801. If it is determined that the AF evaluation value has not fluctuated, the process proceeds to step S811. In step S811, the movement of the focus lens 705 is stopped, and the process returns to step S809.
[0015]
Next, a minute driving operation of the focus lens 705 in the automatic focusing apparatus for a video camera shown in FIG. 7 will be described with reference to FIG.
[0016]
FIG. 9 is a flowchart showing the flow of the minute driving operation in the automatic focusing apparatus for the video camera shown in FIG.
[0017]
9, first, in step S901, the AF evaluation value is fetched from the AF evaluation value processing circuit 712 and stored together with the lens position of the focus lens 705. Next, in step S902, it is determined whether the AF evaluation value captured in step S901 is larger than the previous AF evaluation value. If it is determined in step S901 that the acquired AF evaluation value is smaller than the previous AF evaluation value, the process proceeds to step S903, and it is determined that the acquired AF evaluation value in step S901 is larger than the previous AF evaluation value. If so, the process proceeds to step S906.
[0018]
In step S903, the peak lens position during the movement of the focus lens 705 in one direction is determined and stored in the memory, the peak AF evaluation value is cleared, and the focus lens 705 is driven by a predetermined amount in the direction opposite to the previous time. Thereafter, the process proceeds to step S904.
[0019]
In step S906, the peak AF evaluation value and the peak lens position are updated, and the focus lens 705 is driven a predetermined amount in the previous forward direction, and then the process proceeds to step S904.
[0020]
In step S904, it is determined whether or not the direction determined as the focusing direction for the predetermined number of times is the same. If it is determined that the directions determined as the focusing direction for the predetermined number of times are not the same, the process proceeds to step S905, and it is determined that the directions determined as the focusing direction for the predetermined number of times are the same. If so, the process proceeds to step S908.
[0021]
In step S905, it is determined whether the focus lens 705 repeats reciprocation a predetermined number of times in the same area. If it is determined that the focus lens 705 has repeated the reciprocation a predetermined number of times in the same area, the process proceeds to step S907. The processing operation ends.
[0022]
In step S907, assuming that the focus has been determined, the focus lens 705 is moved to the peak lens position stored in step S903, and then this processing operation ends.
[0023]
In step S908, it is determined that the moving direction of the focus lens 705 has been determined, and this processing operation ends.
[0024]
FIG. 10 is a diagram showing the lapse of time of the operation of the focus lens 705. In FIG. 10, the vertical axis indicates the AF evaluation value, and the horizontal axis indicates the position of the focus lens 705.
[0025]
As shown in FIG. ₀ And the lens position POS ₀ AF evaluation value EV ₀ Then, the focus lens 705 is moved to the lens position POS. ₁ To time T ₁ And the lens position POS ₁ AF evaluation value EV ₁ And the time T ₁ Then, the AF evaluation value EV ₀ , EV ₁ And EV ₁ > EV ₀ If so, move in the forward direction and ₂ Lens position POS ₂ Reach
[0026]
On the other hand, EV ₀ > EV ₁ If so, the focus lens 705 is moved in the opposite direction and the time T ₂ Lens position POS ₀ Return to
[0027]
Next, a method of determining a focal point when the focus lens 705 is minutely driven in the automatic focusing apparatus for a video camera shown in FIG. 7 will be described with reference to FIGS.
[0028]
FIG. 11 is a diagram showing an AF evaluation value (peak AF evaluation value) and a lens position (peak lens position) at which a peak is held, and FIG. 12 is a diagram showing a relationship between the lens position and the AF evaluation value. In the graph, the horizontal axis represents the lens position, the vertical axis represents the AF evaluation value, the arrow represents the movement of the focus lens 705, and the vertical bar represents the AF evaluation value.
[0029]
FIG. 12 shows a state immediately before the stop of focusing after reciprocating several times before and after the focal point. The initial lens position of the focus lens 705 in FIG. 12 is the most infinite.
[0030]
First, the lens position POS ₀ , AF evaluation value EV ₀ Take in. And the peak hold value is also determined by the lens position POS. ₀ , AF evaluation value EV ₀ It becomes. From there, the focus lens 705 moves one step closer as shown by 1201 in FIG. ₁ , AF evaluation value EV ₁ Take in. Here, the AF evaluation value increases (EV ₁ > EV ₀ ), The focus lens 705 continues to move in the same direction as indicated by reference numeral 1202 in FIG. ₁ , AF evaluation value EV ₁ It becomes.
[0031]
Next, the lens position POS ₂ , AF evaluation value EV ₂ Take in. Here, the AF evaluation value increases (EV ₂ > EV ₁ ), The focus lens 705 continues to move in the same direction as indicated by reference numeral 1202 in FIG. ₂ , AF evaluation value EV ₂ It becomes.
[0032]
Next, the lens position POS ₃ , AF evaluation value EV ₃ Take in. Here, the AF evaluation value decreases (EV ₃ <EV ₂ ), The direction of movement of the focus lens 705 is reversed, and the closest lens position at infinity is set to the lens position POS at infinity. ₂ Is determined and stored. Then, the peak hold value is cleared in preparation for the movement of the focus lens 705 in the opposite direction. Here, assuming that a predetermined time of the focus determination has elapsed, the last stored peak lens position POS ₂ Is the focusing lens position.
[0033]
Next, a hill-climbing drive operation of the focus lens 705 in the automatic focusing apparatus for a video camera shown in FIG. 7 will be described with reference to FIG.
[0034]
FIG. 13 is a flowchart showing a flow of a hill-climbing drive operation of the focus lens 705 in the automatic focus adjusting device of the video camera shown in FIG.
[0035]
First, in step S1301, an AF evaluation value is fetched from the AF evaluation value processing circuit 712. Next, in step S1302, it is determined whether the AF evaluation value captured in step S1301 is larger than the previous AF evaluation value. If it is determined in step S1301 that the acquired AF evaluation value is larger than the previous AF evaluation value, the process proceeds to step S1303, and it is determined that the acquired AF evaluation value in step S1301 is smaller than the previous AF evaluation value. If so, the process proceeds to step S1304.
[0036]
In step S1303, after the focus lens 705 is driven at a predetermined speed in the previous forward direction, the processing operation ends. In step S1304, it is determined whether the AF evaluation value has exceeded a peak. If it is determined that the AF evaluation value does not exceed the peak, the process proceeds to step S1305, and if it is determined that the AF evaluation value exceeds the peak, this processing operation ends.
[0037]
In step S1305, after the focus lens 705 is driven at a predetermined speed in the direction opposite to the previous time, the processing operation ends.
[0038]
FIG. 14 is a diagram for explaining the operation of the focus lens 705. In FIG. 14, the vertical axis indicates the AF evaluation value, and the horizontal axis indicates the lens position.
[0039]
In FIG. 14, since A has decreased beyond the peak, it is determined that there is a focal point, the hill-climbing operation of the focus lens 705 is terminated, and the operation shifts to the minute driving operation. On the other hand, since B has no peak and decreases, it is determined that the moving direction of the focus lens 705 is wrong, the moving direction is reversed, and the hill-climbing operation of the focus lens 705 is continued.
[0040]
As described above, according to the automatic focus adjustment device in the conventional video camera, the focus lens 705 is moved while repeating the restart determination, the micro drive, the hill-climbing drive, the micro drive, and the restart determination, and the AF evaluation value is constantly set. The focus state is maintained by controlling the AF microcomputer 713 so as to maximize it.
[0041]
[Problems to be solved by the invention]
However, the above conventional example has the following problems.
[0042]
In other words, since the maximum lens position of the AF evaluation value during the movement of the focus lens 705 in one direction was set as the focal point, the AF happened to fluctuate due to noise or the like, and the maximum lens position of the AF evaluation value was erroneously determined. In such a case, there is a problem that an erroneous lens position is set as a focusing lens position.
[0043]
In order to solve such a problem, conventionally, as disclosed in JP-A-2002-350712, the focus lens position is determined from the AF evaluation values at a plurality of lens positions while the focus lens is moving in one direction. Although a method of determining the AF evaluation value has been proposed, even in this method, only the value during the movement of the focus lens in one direction is used. It is difficult, and there is a problem that an erroneous lens position may be used as a focusing lens position.
[0044]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the related art, and an object of the present invention is to provide an automatic focusing apparatus capable of focusing with high accuracy.
[0045]
[Means for Solving the Problems]
In order to achieve the above object, an automatic focus adjustment device of the present invention takes out a predetermined frequency component of a video signal obtained from an imaging unit by photographing a subject as a focus voltage, and maximizes the focus voltage. An automatic focus adjustment device for adjusting a focus by moving a focus adjustment member in an optical axis direction by a moving unit, wherein a position where a focus voltage is maximized while the focus adjustment member is moving in one direction is obtained. Holding means for holding the focus voltage; determining means for determining a focus position from a focus adjustment member position where the focus voltage is maximized while moving in a plurality of directions; And stopping means for stopping the focus adjusting member at the in-focus position determined by the determining means.
[0046]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.
[0047]
(First Embodiment)
First, a first embodiment of the present invention will be described with reference to FIGS.
[0048]
It should be noted that the basic configuration of a video camera, which is an imaging device having the focus adjusting device according to the present embodiment, is the same as that of the above-described conventional example shown in FIG.
[0049]
Control of the AF microcomputer 713 in the automatic focusing apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 corresponds to FIG. 9 of the above-described conventional example.
[0050]
Steps S101 to S106 and step S108 in FIG. 1 are the same as steps S901 to S906 and step S908 in FIG. 9 of the above-described conventional example, and a detailed description of each processing step will be omitted. Only the processing steps unique to the embodiment will be described.
[0051]
If it is determined in step S105 that the focus lens 705 has repeated the reciprocation a predetermined number of times in the same area, the process proceeds to step S107. After moving the focus lens 705 to the position, the processing operation ends.
[0052]
Next, a method of determining a focal point in the automatic focusing apparatus according to the present embodiment will be described with reference to FIGS.
[0053]
FIG. 2 is a diagram illustrating an AF evaluation value and a lens position at which a peak is held, and FIG. 3 is a diagram illustrating a relationship between the lens position and the evaluation value.
[0054]
3, the horizontal axis indicates the lens position, the vertical axis indicates the magnitude of the AF evaluation value, the arrow indicates the movement of the focus lens 705, and the vertical bar indicates the magnitude of the AF evaluation value.
[0055]
FIG. 3 shows a state immediately before the stop of focusing after the focus lens 705 has reciprocated several times before and after the focal point, and the initial lens position of the focus lens 705 in FIG. 3 is the closest side. .
[0056]
First, the lens position POS ₀ , AF evaluation value EV ₀ Take in. And the peak hold value is also determined by the lens position POS. ₀ , AF evaluation value EV ₀ It becomes. Then, as indicated by reference numeral 301 in FIG. 3, the focus lens 705 moves one step closer to the lens position POS. ₁ , AF evaluation value EV ₁ Take in. Here, the AF evaluation value increases (EV ₁ > EV ₀ ), The focus lens 705 continues to move in the same direction as indicated by reference numeral 302 in FIG. 3, and the peak hold value is changed to the lens position POS. ₁ , AF evaluation value EV ₁ It becomes.
[0057]
Next, the lens position POS ₂ , AF evaluation value EV ₂ Where the AF evaluation value increases (EV ₂ > EV ₁ 3), the focus lens 705 continues to move in the same direction as indicated by reference numeral 303 in FIG. ₂ , AF evaluation value EV ₂ It becomes.
[0058]
Next, the lens position POS ₃ , AF evaluation value EV ₃ Take in. Here, the AF evaluation value decreases (EV ₃ <EV ₂ ), The direction of movement of the focus lens 705 is reversed, and the peak lens position from the closest to infinity is the lens position POS. ₂ Is determined and stored. Then, the peak hold value is cleared in preparation for the movement of the focus lens 705 in the opposite direction.
[0059]
Next, as indicated by reference numeral 304 in FIG. 3, the focus lens 705 moves to the close side by one step, and its lens position POS ₂ , AF evaluation value EV ₄ Where the AF evaluation value increases (EV ₄ > EV ₃ 3), the focus lens 705 continues to move in the same direction as indicated by 305 in FIG. 3, and the peak hold value is changed to the lens position POS. ₂ , AF evaluation value EV ₄ It becomes.
[0060]
Next, the lens position POS ₁ , AF evaluation value EV ₅ Where the AF evaluation value increases (EV ₅ > EV ₄ 3), the focus lens 705 continues to move in the same direction as indicated by 306 in FIG. 3, and the peak hold value is changed to the lens position POS. ₁ , AF evaluation value EV ₅ It becomes.
[0061]
Next, the lens position POS ₀ , AF evaluation value EV ₆ Take in. Here, the AF evaluation value decreases (EV ₆ <EV ₅ ), The direction of movement of the focus lens 705 is reversed, and the peak lens position at the nearest ← infinity is the lens position POS. ₁ Is determined and stored. Then, the peak hold value is cleared in preparation for the movement of the focus lens 705 in the opposite direction. Here, assuming that a predetermined time for the focus determination has elapsed, the closest previous lens position ← the peak lens position POS at infinity. ₁ And the closest previous position → the peak lens position POS at infinity ₂ The average value of this is set as the focusing lens position.
[0062]
In the present embodiment, the average value of the two peak lens positions is set as the focusing lens position. However, when the average value of more peak lens positions is set as the focusing lens position, the focusing accuracy becomes higher. At this time, although depending on the actuator, the peak lens position may be different depending on the driving direction of the focus lens 705 such as the reversal hysteresis, and therefore, the same number of closest to infinite peak lens positions and closest to infinite peak lens positions is included. Therefore, it is desirable to use the even number of peak lens positions to obtain the focal point.
[0063]
As described in detail above, according to the automatic focus adjustment apparatus according to the present embodiment, the focus position is determined from the position of the focus lens 705 (the position of the focus adjustment member) at which the focus voltage is maximized a plurality of times. Therefore, the influence of the erroneous determination of the focus voltage at one time can be eliminated, and focusing can be performed with high accuracy.
[0064]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0065]
It should be noted that the basic configuration of a video camera, which is an imaging device having the focus adjusting device according to the present embodiment, is the same as that of the above-described conventional example shown in FIG.
[0066]
Control of the AF microcomputer 713 in the automatic focusing device according to the present embodiment will be described with reference to FIG. FIG. 4 corresponds to FIG. 9 of the above-described conventional example.
[0067]
Step S401, step S402, step S404, step S405 and step S408 in FIG. 4 are the same as step S901, step S902, step S904, step S905 and step S908 in FIG. The description will be omitted, and only the processing steps unique to the present embodiment will be described.
[0068]
If it is determined in step S402 that the AF evaluation value captured in step S401 is smaller than the previous AF evaluation value, the process proceeds to step S403, and it is determined that the AF evaluation value captured in step S401 is larger than the previous AF evaluation value. If so, the process proceeds to step S406.
[0069]
In step S403, after driving the focus lens 705 by a predetermined amount in the direction opposite to the previous direction, the process proceeds to step S404.
[0070]
In step S406, after the focus lens 705 is driven by a predetermined amount in the previous forward direction, the process proceeds to step S404.
[0071]
If it is determined in step S405 that the focus lens 705 has repeated the reciprocation a predetermined number of times in the same area, the process proceeds to step S407, where it is determined that the focus has been determined, and the past peak lens position (stored in step S401). After the focus lens 705 is moved to the average lens position (a plurality of peak lens positions), this processing operation ends.
[0072]
Next, a method of determining a focal point in the automatic focusing apparatus according to the present embodiment will be described with reference to FIG.
[0073]
FIG. 5 is a diagram showing the relationship between the lens position and the AF evaluation value in the automatic focusing apparatus according to the present embodiment. In FIG. 5, the horizontal axis represents the lens position, the vertical axis represents the AF evaluation value, and the arrow. Indicates the movement of the lens, and the vertical bar indicates the AF evaluation value.
[0074]
FIG. 5 shows a state immediately before the stop of focusing after the focus lens 705 has reciprocated several times before and after the focal point, and the initial lens position of the focus lens 705 in FIG. 5 is the closest position. .
[0075]
First, the lens position POS ₀ , AF evaluation value EV ₀ Take in. From there, the focus lens 705 moves one step closer as indicated by 501 in FIG. ₁ , AF evaluation value EV ₁ Take in. Here, the AF evaluation value increases (EV ₁ > EV ₀ 5), the focus lens 705 continues to move in the same direction as indicated by 502 in FIG.
[0076]
Next, the lens position POS ₂ , AF evaluation value EV ₂ Where the AF evaluation value increases (EV ₂ > EV ₁ ), The focus lens 705 continues to move in the same direction as indicated by 503 in FIG.
[0077]
Next, the lens position POS ₃ , AF evaluation value EV ₃ Take in. Here, the AF evaluation value decreases (EV ₃ <EV ₂ ), The moving direction of the focus lens 705 is reversed.
[0078]
Next, as indicated by reference numeral 504 in FIG. ₂ , AF evaluation value EV ₄ Take in. Here, the AF evaluation value increases (EV ₄ > EV ₃ 5), the focus lens 705 advances in the same direction as indicated by 505 in FIG.
[0079]
Next, the lens position POS ₁ , AF evaluation value EV ₅ Where the AF evaluation value increases (EV ₅ > EV ₄ 5), the focus lens 705 advances in the same direction as indicated by 506 in FIG.
[0080]
Next, the lens position POS ₀ , AF evaluation value EV ₆ Take in. Here, the AF evaluation value decreases (EV ₆ <EV ₅ ), The moving direction of the focus lens 705 is reversed. Here, assuming that a predetermined time for the focus determination has elapsed, the past six lens positions POS ₁ , POS ₂ , POS ₃ , POS ₂ , POS ₁ , POS ₀ Is defined as the focusing lens position.
[0081]
In the present embodiment, the average value of the six lens positions is set as the focusing lens position. However, when the average value of more lens positions is set as the focusing lens position, the focusing accuracy becomes higher. At this time, if the focusing lens position is calculated based on a lens position that is an integral multiple of the driving cycle required for reciprocation near the AF focusing point, an accurate focusing point can be obtained.
[0082]
As described above, according to the automatic focus adjustment apparatus according to the present embodiment, since the focus position is determined from the positions of the plurality of focus lenses 705 (the positions of the focus adjustment members) immediately before the focus, a single focus voltage is set. Can be eliminated, and focusing can be performed with high accuracy.
[0083]
(Other embodiments)
A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and a computer (or CPU, MPU, or the like) of the system or apparatus stores the program code stored in the storage medium. It is needless to say that the present invention can also be achieved by reading and executing.
[0084]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
[0085]
Further, as a storage medium for supplying the program code, for example, RAM, NV-RAM, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW , A DVD (DVD-ROM, DVD-R, DVD-RW, etc.), a magnetic tape, a non-volatile memory card, another ROM, etc., as long as the program code can be stored, or a download via a network. Can be used.
[0086]
When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also an OS (Operating System) or the like running on the computer based on the instruction of the program code. Performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0087]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that a CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0088]
Although various examples and embodiments of the present invention have been described above, those skilled in the art will appreciate that the spirit and scope of the present invention are not limited to the specific description and drawings in this specification, and are not limited thereto. It goes without saying that it is possible to cover various modifications and changes all set forth in the claims.
[0089]
Examples of embodiments of the present invention are listed below.
[0090]
[Embodiment 1] A predetermined frequency component of a video signal obtained from an imaging unit by photographing a subject is extracted as a focus voltage, and a focus adjustment member is moved in the optical axis direction by a movement unit so as to maximize the focus voltage. An automatic focus adjustment device that performs focus adjustment by
Holding means for finding and holding a position where the focus voltage is maximized while the focus adjustment member is moving in one direction,
Determining means for determining a focus position from a focus adjustment member position where the focus voltage is maximized while moving in a plurality of directions;
Stopping means for stopping the focus adjusting member at the in-focus position determined by the determining means after reciprocating the peak of the focus voltage a predetermined number of times.
[0091]
[Embodiment 2] The automatic focusing apparatus according to Embodiment 1, wherein the plurality is an even number.
[0092]
[Embodiment 3] A predetermined frequency component of a video signal obtained from an imaging unit by photographing a subject is extracted as a focus voltage, and a focus adjustment member is moved in the optical axis direction by a movement unit so as to maximize the focus voltage. An automatic focus adjustment device that performs focus adjustment by
Holding means for finding and holding a position where the focus voltage is maximized while the focus adjustment member is moving in one direction,
Determining means for determining a focus position from an average position of focus adjustment member positions where the focus voltage is maximized while moving in a plurality of directions;
Stopping means for stopping the focus adjusting member at the in-focus position determined by the determining means after reciprocating the peak of the focus voltage a predetermined number of times.
[0093]
[Embodiment 4] The automatic focusing apparatus according to Embodiment 3, wherein the plurality is an even number.
[0094]
[Embodiment 5] A predetermined frequency component of a video signal obtained from an imaging unit by photographing a subject is extracted as a focal voltage, and a focusing unit is moved in the optical axis direction by a moving unit so as to maximize the focal voltage. An automatic focus adjustment device that performs focus adjustment by
Holding means for holding the focus adjusting member position within a predetermined time;
Determining means for determining a focus position from a plurality of focus adjusting member positions held by the holding means;
Stopping means for stopping the focus adjusting member at the in-focus position determined by the determining means after reciprocating the peak of the focus voltage a predetermined number of times.
[0095]
[Sixth Embodiment] The automatic focus adjustment apparatus according to the fifth embodiment, wherein the predetermined time is an integral multiple of a time required to reciprocate a peak of the focus voltage before stopping focusing.
[0096]
[Embodiment 7] A predetermined frequency component of a video signal obtained from an imaging unit by taking an image of a subject is extracted as a focus voltage, and a focus adjustment member is moved in the optical axis direction by a movement unit so as to maximize the focus voltage. An automatic focus adjustment device that performs focus adjustment by
Holding means for holding the focus adjusting member position within a predetermined time;
Determining means for determining an average position of the plurality of focus adjustment member positions held by the holding means as a focus position;
Stopping means for stopping the focus adjusting member at the in-focus position determined by the determining means after reciprocating the peak voltage of the focus voltage a predetermined number of times.
[0097]
[Eighth Embodiment] The automatic focus adjustment apparatus according to the seventh embodiment, wherein the predetermined time is an integral multiple of a time required to reciprocate a peak of the focus voltage before stopping focusing.
[0098]
[Embodiment 9] A predetermined frequency component of a video signal obtained in an imaging step by taking an image of a subject is extracted as a focus voltage, and a focus adjustment member is moved in the optical axis direction by a movement step so as to maximize the focus voltage. An automatic focus adjustment method for performing focus adjustment by
A holding step of finding and holding a position where the focus voltage is maximized while the focus adjustment member is moving in one direction,
A determination step of determining a focus position from a focus adjustment member position where the focus voltage is maximized while moving in a plurality of directions;
Stopping the focus adjustment member at the focus position determined by the determination step after reciprocating the peak of the focus voltage a predetermined number of times.
[0099]
[Embodiment 10] The automatic focusing method according to Embodiment 9, wherein the plurality is an even number.
[0100]
[Embodiment 11] A predetermined frequency component of a video signal obtained by capturing an image of a subject by taking a positive image is extracted as a focus voltage, and a focus adjustment member is moved in the optical axis direction by a moving step so as to maximize the focus voltage. An automatic focus adjustment method for performing focus adjustment by
A holding step of finding and holding a position where the focus voltage is maximized while the focus adjustment member is moving in one direction,
A determination step of determining a focus position from an average position of focus adjustment member positions where the focus voltage is maximized while moving in a plurality of the one directions;
Stopping the focus adjustment member at the focus position determined in the determination step after reciprocating the peak of the focus voltage a predetermined number of times.
[0101]
[Embodiment 12] The automatic focusing method according to Embodiment 11, wherein the plurality is an even number.
[0102]
[Thirteenth Embodiment] A predetermined frequency component of a video signal obtained in an imaging step by photographing a subject is extracted as a focus voltage, and a focus adjustment member is moved in the optical axis direction by a movement step so as to maximize the focus voltage. An automatic focus adjustment method for performing focus adjustment by
A holding step of holding the focus adjustment member position within a predetermined time,
A determining step of determining a focus position from a plurality of focus adjusting member positions held by the holding step;
Stopping the focus adjustment member at the focus position determined by the determination step after reciprocating the peak of the focus voltage a predetermined number of times.
[0103]
[Embodiment 14] The automatic focus adjustment method according to Embodiment 13, wherein the predetermined time is an integral multiple of a time required to reciprocate a peak of the focus voltage before stopping focusing.
[0104]
[Embodiment 15] A predetermined frequency component of a video signal obtained by an imaging process by photographing a subject is extracted as a focus voltage, and the focus adjustment member is moved in the optical axis direction by a movement process so as to maximize the focus voltage. An automatic focus adjustment method for performing focus adjustment by
A holding step of holding the focus adjustment member position within a predetermined time,
A determining step of determining an average position of the plurality of focus adjustment member positions held by the holding step as a focus position;
Stopping the focus adjusting member at the in-focus position determined by the determining step after reciprocating the peak of the focus voltage a predetermined number of times.
[0105]
[Embodiment 16] The automatic focus adjustment method according to embodiment 15, wherein the predetermined time is an integral multiple of a time required to reciprocate a peak of the focus voltage before stopping focusing.
[Embodiment 17] A control program comprising a program code for causing a computer to execute each step provided in the automatic focusing method according to any one of Embodiments 9 to 16.
[Embodiment 18] A storage medium storing the control program according to Embodiment 17.
[0106]
【The invention's effect】
As described above, according to the automatic focusing apparatus of the present invention, it is possible to perform focusing with high accuracy.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a flow of a minute driving operation in an automatic focusing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating an AF evaluation value and a lens position that are peak-held in the automatic focusing apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating a relationship between a lens position and an AF evaluation value in the automatic focusing apparatus according to the first embodiment of the present invention.
FIG. 4 is a flowchart illustrating a flow of a minute driving operation in the automatic focusing apparatus according to the second embodiment of the present invention.
FIG. 5 is a diagram showing a relationship between a lens position and an AF evaluation value in an automatic focusing device according to a second embodiment of the present invention.
FIG. 6 is a diagram showing a relationship between a focus lens position and a focus voltage level in a conventional automatic focusing device.
FIG. 7 is a block diagram illustrating a configuration of a video camera which is an imaging device including a conventional automatic focusing device.
8 is a flowchart showing a flow of an AF operation in the automatic focus adjustment device of the video camera shown in FIG.
FIG. 9 is a flowchart showing a flow of a minute driving operation in the automatic focusing apparatus of the video camera shown in FIG. 7;
FIG. 10 is a diagram showing a relationship between a lens position and an AF evaluation value in the automatic focusing device of the video camera shown in FIG. 7;
11 is a diagram illustrating an AF evaluation value and a lens position that are peak-held in the automatic focusing apparatus of the video camera shown in FIG. 7;
12 is a diagram showing a relationship between a lens position and an AF evaluation value in the automatic focusing device of the video camera shown in FIG. 7;
13 is a flowchart showing a flow of a hill-climbing drive operation of a focus lens in the automatic focus adjusting device of the video camera shown in FIG. 7;
FIG. 14 is a diagram showing a relationship between a lens position and an AF evaluation value in the automatic focusing device of the video camera shown in FIG. 7;
[Description of sign]
701 Fixed first group lens
702 Zoom lens
703 aperture
704 Fixed second group lens
705 Focus Competition Lens (Focus Lens)
706 CCD
707 CDS / AGC
708 Camera signal processing circuit
709 Recording device
710 Focus Compensation Lens Motor
711 Focus Competition Lens Driver
712 AF evaluation value processing circuit
713 AF microcomputer
714 location memory
715 Monitor device

Claims (1)

A predetermined frequency component of a video signal obtained from the imaging means by taking an image of a subject is taken out as a focus voltage, and the focus adjustment member is moved in the optical axis direction by the movement means so as to maximize this focus voltage. An automatic focusing device that performs
Holding means for finding and holding a position where the focus voltage is maximized while the focus adjustment member is moving in one direction,
Determining means for determining a focus position from a focus adjustment member position where the focus voltage is maximized while moving in a plurality of directions;
Stopping means for stopping the focus adjusting member at the in-focus position determined by the determining means after reciprocating the peak of the focus voltage a predetermined number of times.

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