JP4510193B2 - Focus adjustment device and focus adjustment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a focus adjustment device and a focus adjustment method used for various video cameras and the like.
[0002]
[Prior art]
In recent years, video devices such as video cameras have made remarkable progress, and auto focus control, auto iris control, zoom function, etc. are equipped as standard, improving operability and increasing functionality in every part. ing.
[0003]
By the way, when looking at the autofocus device, the imaging lens or the like detects the sharpness of the screen from the video signal obtained by photoelectrically converting the subject image, and sets the focus lens position so that it becomes the maximum AF evaluation value. The method of controlling and performing focus adjustment is becoming mainstream.
[0004]
As the AF evaluation value, the level of a high frequency component of a video signal extracted by a band pass filter in a certain band is generally used. When a normal subject image is photographed, the value increases as the focus is achieved as shown in FIG. 2, and the point at which the level becomes maximum is set as the in-focus position.
[0005]
In an actual video camera, as shown in FIG. 1, the AF microcomputer 115 moves the focus lens 105 so that the output signal level of the AF evaluation value processing circuit 114 is maximized, and performs automatic focus adjustment.
[0006]
Then, as shown in FIG. 3, the AF microcomputer 115 performs a slight drive operation of the focus lens 105, and performs focusing processing when it is determined that the focus lens 105 is in focus. When it is determined that the subject is not in focus, if the direction in which the AF evaluation value increases is determined, the focus lens 105 is driven (hill-climbing drive) in that direction. Then, when the peak of the AF evaluation value is reached, the minute driving operation is performed again. Thereafter, when it is determined that the subject is in focus, the AF evaluation value at that time is compared with the latest AF evaluation value, and if there is a difference of a predetermined level or more, it is determined that the system is restarted, and a minute driving operation is performed.
[0007]
Next, a conventional minute driving operation will be described with reference to FIG. Step S901 indicates the start of processing. In step S902, an AF evaluation value is fetched from the AF evaluation value processing circuit. In step S903, if the evaluation value fetched in step S902 is smaller than the previous evaluation value, the process proceeds to step S904, and the evaluation value fetched in step S902 is the previous evaluation value. If greater than the evaluation value, the process proceeds to step S905. In step S904, the focus lens is driven by a predetermined amount in the reverse direction of the previous time. On the other hand, in step S905, the focus lens is driven by a predetermined amount in the previous forward direction.
[0008]
In step S906, if the direction determined to be the in-focus direction is the same for a predetermined number of times, the process proceeds to step S907. If the direction has not been continued for the predetermined number of times in the same direction, the process proceeds to step S908. In step S908, if the force lens is in the same area for a predetermined time, that is, if the lens position remains in the predetermined range, the process proceeds to step S909, and if the focus lens is not in the same area for a predetermined time, the process proceeds to step S910 and the process is terminated. In step S907, it is determined that the direction can be determined, and the process proceeds to step S910 to end the process. In step S909, it is determined that the in-focus state has been determined, and the process ends.
[0009]
In this way, the camera AF microcomputer 115 is controlled so that the AF evaluation value is always maximized by moving the focus lens while repeating the restart determination → minor drive → mountain climbing drive → minor drive → restart determination.
[0010]
[Problems to be solved by the invention]
However, the conventional focusing device as described above has the following problems.
[0011]
Since the AF evaluation value is generally the level of the high-frequency component of the video signal extracted by a band pass filter in a certain band, the peak level of the evaluation value at the focal point is not constant depending on the subject.
[0012]
Even if the AF evaluation value is the same, one of them may be in focus and the other may not be in focus.
[0013]
Therefore, for example, when the brightness level of the subject changes, even if the evaluation value increases when the lens is moved, it may actually be out of focus, and just because the evaluation value increases, the lens moves in the same direction. When I was doing it, there was a case where blur was conspicuous.
[0014]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a focus adjustment device and a focus adjustment method capable of reliably performing focus adjustment.
[0015]
[Means for Solving the Problems]
The focus adjustment apparatus and the focus adjustment method of the present invention are configured as follows.
[0016]
Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. If the sharpness of the image acquired by moving the focus lens is higher than the sharpness of the previously acquired image, the device is moved in the same direction as the movement direction of the focus lens, and if low, the focus lens And moving the focus lens in the same direction as the movement direction when the movement direction of the focus lens is the same for a predetermined number of times, and prohibiting the movement of the focus lens in the same direction as the movement direction. If the lens is moved beyond a predetermined range during a predetermined time, the focus lens is moved in that direction. Comprising a control means for controlling to move at a faster rate.
[0017]
Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. If the sharpness of the image acquired by moving the focus lens is higher than the sharpness of the previously acquired image, the device is moved in the same direction as the movement direction of the focus lens, and if low, the focus lens When the movement direction of the focus lens is the same continuously for a predetermined number of times , the focus lens is controlled to move in the direction opposite to the movement direction. If the focus lens is moved beyond a predetermined range during a predetermined time, the focus lens is moved faster in that direction. Comprising a control means for moving at speed.
[0018]
Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. An apparatus for comparing increase / decrease of the sharpness of the image before and after the focus lens moves by a predetermined amount, and for determining the direction in which the sharpness of the image increases; The focus lens is moved in a direction in which the sharpness of the focus lens increases, and the direction of movement of the focus lens is compared when the direction of movement of the focus lens accompanying the determination of the comparison determination unit is the same for a predetermined number of times. determining controls to reverse regardless of the direction in which the image sharpness is increased by the determination means, the focus lens for a predetermined time When it is moved beyond a predetermined range during has a control means for controlling to move the focus lens in the direction at a faster rate.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a configuration of a video camera according to the present invention. In FIG. 1, 101 is a fixed first lens group, 102 is a variable power lens for zooming, 103 is a stop, 104 is a fixed second lens group, and 105 is a function for correcting movement of the focal plane due to zooming. And a focus lens that combines the functions of focusing.
[0026]
Reference numeral 106 denotes a CCD serving as an image sensor, and 107 denotes an AGC that amplifies the output of the CCD 106. The amplification factor is adjusted by a signal from a camera AF microcomputer 115 described later. Reference numeral 108 denotes a camera signal processing circuit. Reference numerals 110 and 112 denote actuators (motors) for moving the variable magnification lens 102 and the focus lens 105, respectively. Reference numerals 111 and 113 denote drivers for driving the actuators 110 and 112 by signals from a camera AF microcomputer 115 described later.
[0027]
Reference numeral 114 denotes an AF evaluation value processing circuit that extracts a high frequency component used for focus detection from the output signal of the image sensor 106 as a focus voltage (AF evaluation value) shown in FIG. 2, and 115 comprehensively controls the entire system. The AF microcomputer controls the actuators 110 and 112 based on the output of the AF evaluation value processing circuit 114.
[0028]
In the video camera having the above configuration, the camera AF microcomputer 115 (prohibiting means, comparison determining means, control means) moves the focus lens (focus adjustment member) 105 in the optical axis direction by the motor 112 and the driver 113 as moving means. The focus adjustment operation is performed so that the evaluation value is maximized. The focus lens 105 compares the increase and decrease of the AF evaluation value before and after the operation by a predetermined amount to determine the direction in which the AF evaluation value increases, moves the focus lens 105 by a predetermined amount in the determination direction, and the determination direction is When the number of determinations is the same for the same number of times, the movement in that direction is prohibited, and the movement direction of the focus lens 105 is reversed.
[0029]
The control of the camera AF microcomputer 115 will be described in detail with reference to FIGS. The main AF process will be described with reference to FIG. Step S301 indicates the start of processing. In step S302, a minute driving operation is performed, and it is determined which direction is in focus when it is in focus or not in focus. A detailed explanation of the operation will be given later. In step S303, when it is determined that the focus is achieved in step S302, the process proceeds to step S309 to perform a focusing process, and when it is not determined that the focus is achieved in step S302, the process proceeds to step S304.
[0030]
In step S304, if the direction can be determined in step S302, the process goes to step S305 to perform hill climbing processing. If the direction cannot be determined in step S302, the process returns to step S302 to continue the minute driving operation. In step S305, the lens is hill-climbed at high speed in the direction in which the evaluation value increases. A detailed explanation of the operation will be given later.
[0031]
In step S306, if it is determined in step S305 that the vertex of the evaluation value has been exceeded, the process proceeds to step S307. If it is not determined in step S305 that the vertex of the evaluation value has been exceeded, the process returns to step S305 to continue the hill climbing operation. In step S307, the lens is returned to the apex of the evaluation value during hill-climbing driving. In step S308, when returning to the apex in step S307, the process returns to step S302 to perform the minute driving operation again. When not returning to the apex in step S307, the operation returns to step S307 and returns to the apex.
[0032]
Next, the focusing operation from step S309 will be described. In step S309, the AF evaluation value is held. In step S310, the AF evaluation value held in step S309 is compared with the latest AF evaluation value. In step S311, if it is determined to be restarted in step S310, the process goes to step S302 to resume the minute driving operation, and if it is not determined to be restarted in step S310, the process goes to step S312. In step S312, the lens is stopped and the process returns to step S310 to continue the restart determination.
[0033]
Here, the minute drive operation (low-speed drive operation) in step 302 will be described in detail. The control of the camera AF microcomputer will be described in detail with reference to FIG. This figure shows the control corresponding to FIG. 9 in the prior art. In addition, the same step number is attached | subjected to the step which performs the process similar to the past.
[0034]
First, the minute driving operation will be described with reference to FIG. Step S901 indicates the start of processing. In step S902, an AF evaluation value is fetched from the AF evaluation value processing circuit 114. In step S903, if the evaluation value fetched in step S902 is smaller than the previous evaluation value, the process proceeds to step S904, and the evaluation value fetched in step S902 is the previous time. If it is larger than the evaluation value, the process proceeds to step S401.
[0035]
In step S401, if it has moved in the same direction for a predetermined number of times, the process proceeds to step S904, and if it has not moved in the same direction for a predetermined number of times, the process proceeds to step S905. In step S904, the focus lens is driven by a predetermined amount in the reverse direction of the previous time. In step S905, the focus lens is driven by a predetermined amount in the previous forward direction. That is, when moving in the same direction a predetermined number of times or more, it is reversed even if the evaluation value increases. As a result, when the evaluation value increases due to a change in the subject, there is no possibility that the focus lens 105 continues to move in the blurring direction by mistake.
[0036]
In step S906, if the direction determined to be the in-focus direction is the same continuously for a predetermined number of times, the process proceeds to step S907, and if the direction is not continuously continued for the predetermined number of times, the process proceeds to step S908. In step S908, if it is in the same area for a predetermined time, the process proceeds to step S909, and if it is not in the same area for a predetermined time, the process proceeds to step S910 and the process is terminated. In step S907, it is determined that the direction can be determined, and the process proceeds to step S910 to end the process. In step S909, it is determined that the in-focus state has been determined, and the process ends.
[0037]
FIG. 5 shows the time course of the lens operation. Here, the evaluation value A for the charge accumulated in the CCD during _A is taken in by T _A , and the evaluation value B for the charge accumulated in the CCD during _B is taken in by T _{B. In} T _B , the evaluation value is taken A and B are compared, and if A <B, it moves in the forward direction as it is, while if A> B, it is in the reverse direction.
[0038]
Next, the hill climbing operation (high-speed driving operation) in steps 305 and 306 will be described with reference to FIG. Step S601 indicates the start of processing. In step S602, an AF evaluation value is acquired from the AF evaluation value processing circuit. In step S603, if the evaluation value acquired in step S602 is larger than the previous evaluation evaluation value, the process proceeds to step S604, and the evaluation value acquired in step S602 is the previous time. If it is smaller than the evaluation value, the process proceeds to step S605.
[0039]
In step S604, the focus lens is driven at the previous forward speed, and the process returns to step S602. On the other hand, in step S605, if the evaluation value has not decreased beyond the peak, the process proceeds to step S606, and if the evaluation value has decreased beyond the peak, the process proceeds to step S607 to end the process. In step S606, the focus lens is driven at a predetermined speed in the direction opposite to the previous time, and the process returns to step S602.
[0040]
FIG. 7 illustrates the lens operation. Here, since A has decreased beyond the peak, the hill-climbing operation is terminated because there is an in-focus point, and the operation shifts to a minute driving operation. On the other hand, since B has decreased without a peak, the direction is wrong. Invert and continue climbing.
[0041]
3, 4, and 6 are executed by an instruction from the AF microcomputer 115 based on a program stored in advance in a ROM (not shown).
[0042]
As described above, in the minute driving operation, when the evaluation value is increased in the conventional method, the process of step S902 → step S903 → step S905 is performed and the movement continues in the same direction. Then, after the process of step S902 → step S903 → step 401 → step S905 is continuously performed a predetermined number of times, the process of step S902 → step S903 → step S401 → step S905 is performed to continuously move the lens in a predetermined direction. In such a case, the direction is not erroneously determined due to a change in the AF evaluation value due to a change in the subject by reversing once.
[0043]
As shown in FIG. 8 showing the movement of the lens, when the AF evaluation value increases regardless of the movement of the focus lens, in the conventional case, the processing of step S902 → step S903 → step S905 is performed. Since the movement continues in the same direction, the focus lens moves in one direction as shown in FIG. On the other hand, according to the present invention, if the process of step S902 → step S903 → step S401 → step S905 is performed three times continuously, the process of step S902 → step S903 → step S401 → step S904 is performed. As shown in FIG. 8B, it is possible to remain at a specific position, and it is possible to realize a sure focus adjustment.
[0044]
As described above, in this embodiment, when the lens is continuously moved in a predetermined direction, it is reversed once, so that the direction determination is not erroneously caused by the change of the AF evaluation value due to the subject change. For example, when the AF evaluation value increases regardless of the movement of the focus lens, the focus lens moves in one direction as shown in FIG. 8B, it is possible to remain at a specific position as shown in FIG. 8B, and it is possible to realize reliable focus adjustment.
[0045]
【The invention's effect】
As described above, according to the present invention, when the lens continuously moves in a predetermined direction, it is reversed once, so that the direction determination is not erroneous due to the change of the AF evaluation value due to the change of the subject, and the reliable focus is achieved. There is an effect that adjustment can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a video camera according to an embodiment of the present invention. FIG. 2 is a diagram showing a relationship between a focus lens position and a focus voltage level. FIG. Flowchart FIG. 4 is a flowchart showing a minute driving operation of one embodiment. FIG. 5 is a diagram showing a time course of lens operation of one embodiment. FIG. 6 is a flowchart showing a hill-climbing driving operation of one embodiment. FIG. 8 is a diagram showing a lens operation of the embodiment. FIG. 8 is a diagram showing a comparison of lens moving positions. FIG. 9 is a flowchart showing a conventional micro drive operation.
101 First lens group 102 Variable magnification lens 103 Diaphragm 104 Second lens group 105 Focus lens 106 CCD
110 Actuator (Motor)
111 Driver 112 Actuator (Motor)
113 driver 114 AF evaluation value processing circuit 115 camera AF microcomputer (prohibiting means, control means, comparison determination means)

Claims (9)

Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. A device,
If the sharpness of the image acquired by moving the focus lens is higher than the sharpness of the image acquired last time, the image is moved in the same direction as the movement direction of the focus lens. When the movement direction of the focus lens is the same for a predetermined number of times , the focus lens is controlled to be prohibited from moving in the same direction as the movement direction . A focus adjustment device comprising control means for controlling the focus lens to move at a higher speed in the direction when it is moved beyond a predetermined range . Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. A device,
If the sharpness of the image acquired by moving the focus lens is higher than the sharpness of the image acquired last time, the image is moved in the same direction as the movement direction of the focus lens. When the moving direction of the focus lens is the same for a predetermined number of times , the focus lens is controlled to move in a direction opposite to the moving direction, and the focus lens is moved during a predetermined time. A focus adjustment apparatus comprising control means for controlling the focus lens to move at a higher speed in the direction when the lens is moved beyond a predetermined range . Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. A device,
Comparison determination means for comparing the increase and decrease of the sharpness of the image before and after the focus lens moves by a predetermined amount, and determining the direction in which the sharpness of the image increases;
When the focus lens is moved in a direction in which the sharpness of the image is increased in accordance with the determination of the comparison determination unit, and the movement direction of the focus lens in accordance with the determination of the comparison determination unit is the same for a predetermined number of times continuously. The moving direction of the focus lens is controlled to be reversed regardless of the direction in which the image sharpness determined by the comparison / determination means increases , and the focus lens is moved beyond a predetermined range during a predetermined time. And a control means for controlling the focus lens to move at a higher speed in that direction . The control means has a first drive mode for minutely driving the focus lens and a second drive mode for moving the focus lens at a higher speed than the first drive mode. In the first mode, The focus adjustment apparatus according to claim 1 , wherein the prohibition control is performed.   The control means has a first drive mode for finely driving the focus lens and a second drive mode for moving the focus lens at a higher speed than the first drive mode. In the first mode, The focus adjustment apparatus according to claim 2, wherein control is performed so that the moving direction is opposite.   The control means has a first drive mode for finely driving the focus lens and a second drive mode for moving the focus lens at a higher speed than the first drive mode. In the first mode, The focus adjustment apparatus according to claim 3, wherein the inversion is controlled. Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. The focus lens is moved in the same direction as the moving direction of the focus lens if the sharpness of the image acquired by moving the focus lens is higher than the sharpness of the image acquired last time. When the moving direction of the focus lens is the same for a predetermined number of times , the focus lens is prohibited from moving in the same direction as the moving direction. If the focus lens is moved beyond the predetermined range during the time, the focus lens is moved faster in that direction. Focusing method characterized by moving at speed. Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. The focus lens is moved in the same direction as the moving direction of the focus lens if the sharpness of the image acquired by moving the focus lens is higher than the sharpness of the image acquired last time. When the movement direction of the focus lens is the same for a predetermined number of times, the focus lens is moved in a direction opposite to the movement direction, and the focus lens is moved for a predetermined time. The focus lens is moved at a faster speed in that direction. Focusing method comprising Rukoto. Focus adjustment is performed by moving the focus lens in the direction of the optical axis by the moving means so that the sharpness of the image is increased based on a predetermined high-frequency component of the video signal obtained from the imaging means by photographing the subject. A method,
Compare the increase and decrease of the sharpness of the image before and after the focus lens moves a predetermined amount, determine the direction in which the sharpness of the image increases,
The focus lens is moved in a direction in which the sharpness of the image is increased in accordance with the determination, and the moving direction of the focus lens is determined when the movement direction of the focus lens in the determination is the same for a predetermined number of times. The image is reversed regardless of the direction in which the sharpness of the image increases , and when the focus lens is moved beyond a predetermined range during a predetermined time, the focus lens is moved at a higher speed in that direction. in focusing and wherein the Rukoto move.

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