JP3544103B2 - Imaging device and automatic focus adjustment method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image pickup apparatus and an automatic focus adjustment method, and is particularly suitable for use in a case where a subject image is captured while emitting light from a light emitting unit and focus adjustment is performed.
[0002]
[Prior art]
In recent years, in the field of video cameras, attention has been paid to recording new still images in addition to moving image recording. In order to record a high-quality still image, a video camera has been proposed in which a strobe can be mounted to increase the number of shooting opportunities.
[0003]
The strobe includes a strobe provided with an auxiliary light emitting unit for operating an autofocus device before photographing, in addition to the main light emitting unit. In such a strobe, after the auxiliary light emitting unit is turned on to operate the autofocus device to focus, the main light emitting unit is turned on to record a still image on a storage medium.
[0004]
By the way, when looking at an autofocus device of a video camera, an image sensor or the like detects a sharpness of a screen from a video signal obtained by photoelectrically converting a subject image, and positions a focus lens so that the sharpness is maximized. The TVAF system in which focus control is performed by controlling the focus is mainly used.
[0005]
As the evaluation of the sharpness, a level of a high-frequency component of a video signal extracted by a band-pass filter of a certain band (hereinafter, referred to as a focus evaluation value) or the like is generally used. When a normal subject image is photographed, the focus evaluation value increases as the focus becomes higher as shown in the characteristic diagram of FIG. 2, and the point at which the level becomes maximum is defined as the in-focus position.
[0006]
The control operation of the autofocus device of the video camera equipped with a strobe capable of photographing a still image will be described in detail with reference to the flowchart of FIG.
In FIG. 6, step 301 indicates the start of the process. The next step 302 is a process of turning on the auxiliary light emitting unit to prepare for operating the autofocus device.
[0007]
Next, in step 303, a process of taking in a focus evaluation value is performed while the focus lens 105 is driven minutely.
In step 304, based on the focus evaluation value captured in step 303, it is determined whether or not the camera is currently in a focused state based on the result of the minute driving operation. If it is determined that the subject is in the focused state, the focus lens is stopped, and the process proceeds to a still image capturing routine from step 310. If not in the focused state, the process proceeds to step 305.
[0008]
In step 305, it is determined which direction the in-focus point is based on the result of the minute driving operation. If the direction in which the focal point is located can be determined, the process proceeds to step 306, and a hill-climbing operation is performed in the determination direction. If it is not clear which direction the focal point is located in, it repeats the processing from step 303 described above.
[0009]
Step 307 is a step of determining whether or not the focal point has been exceeded, that is, whether or not the vertex of the focus evaluation value has been exceeded. If the result of this determination is that the focus evaluation value has not been exceeded, the process returns to step 306 to continue the hill-climbing process. If it has exceeded, the sequence proceeds to steps 308 and 309 to return the focus lens to the top.
[0010]
By performing the processing of steps 308 and 309, the focus lens can be controlled to the position where the focus evaluation value becomes the maximum. However, when returning to the vertex, the subject changes due to panning or the like. In some cases, you may not know if the position is a true vertex.
[0011]
Therefore, when the focus lens arrives at the vertex, in order to confirm that the current position is the true vertex, that is, the in-focus point, return to the processing from step 303 and perform the fine driving operation again. I have.
[0012]
If it is determined in step 304 that the image is in focus, the process proceeds to a still image capturing routine from step 310.
In step 310, first, the movement of the focus lens is stopped in step 310. Next, in step 311, the auxiliary light emitting unit is turned off. Next, in step 312, the main light emitting section is turned on to increase the illuminance of the subject, and a still image is captured in that state. Then, after the capture of the still image is completed, the process proceeds to step 313, and the focusing process is completed.
[0013]
[Problems to be solved by the invention]
As described in the above example, when the focus is adjusted by illuminating the subject with the auxiliary light emitting unit, the auxiliary light emitting unit is turned on during the entire focus adjustment period due to durability and power consumption of the auxiliary light emitting unit. The auxiliary light emitting unit is turned on or off because it cannot be left as it is.
[0014]
However, the evaluation value of AF is different between when the auxiliary light emitting unit is turned on and when it is turned off. Therefore, if the auxiliary light is flickered at random timing, accurate AF control can be performed. There was a problem that it could not be done.
[0015]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to appropriately protect an auxiliary light emitting unit and accurately perform AF control. The purpose is to be able to do.
[0016]
[Means for Solving the Problems]
An imaging apparatus according to the present invention is configured such that a predetermined high-frequency component of a video signal obtained from an imaging unit is extracted as a focus evaluation value, and the focus adjustment is performed so that the focus evaluation value is maximized. In synchronization with a vertical scanning section including a blanking section that is a section for a video signal and a video section that is a section for a video signal, the light emitting section is intermittently turned on during the focus adjustment operation, and the lighting time of the light emitting section is reduced. It is characterized in that it is twice as long as the vertical scanning section, and the light emission time of the light emitting means is the vertical scanning section.
Another feature of the present invention is an imaging apparatus that extracts a predetermined high-frequency component of a video signal obtained from an imaging unit as a focus evaluation value and performs focus adjustment so that the focus evaluation value is maximized. In synchronization with a vertical scanning section including a blanking section that is a section for a vertical synchronization signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and The focus adjustment is performed using an average focus evaluation value of a focus evaluation value when the light emitting unit is turned on and a focus evaluation value when the light emitting unit is not turned on.
[0017]
In the automatic focus adjustment method of the present invention, a predetermined high-frequency component of a video signal obtained from an imaging unit is extracted as a focus evaluation value, and the focus adjustment is performed so that the focus evaluation value is maximized. In synchronization with a vertical scanning section including a blanking section that is a section for a synchronization signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and the light emitting unit is turned on. The lighting time is twice as long as the vertical scanning section, and the light-off time of the light emitting means is the vertical scanning section.
Another feature of the present invention is that an automatic focus adjustment for extracting a predetermined high-frequency component of a video signal obtained from an imaging unit as a focus evaluation value and performing focus adjustment so that the focus evaluation value is maximized. In the method, the light emitting unit is intermittently turned on during the focus adjustment operation in synchronization with a vertical scanning section including a blanking section that is a section for a vertical synchronization signal and a video section that is a section for a video signal. The focus adjustment is performed using the average focus evaluation value of the focus evaluation value when the light emitting unit is turned on and the focus evaluation value when the light emitting unit is not turned on.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a preferred embodiment of an image pickup apparatus, an automatic focus adjustment method, an automatic focus adjustment apparatus, and a storage medium according to the present invention, and the configuration of an actual video camera will be described in detail.
[0033]
In FIG. 1, reference numeral 101 denotes a fixed first group lens, 102 denotes a variable power lens for performing zooming, 103 denotes an aperture, 104 denotes a fixed second group lens, and 105 denotes a function for correcting movement of a focal plane due to zooming. And a focus compensating lens (hereinafter, focus lens) having a function of focusing.
[0034]
Reference numeral 106 denotes a CCD serving as an image sensor, and 107 denotes an AGC for amplifying the output of the CCD 106.
Reference numeral 108 denotes a camera signal processing circuit, and reference numeral 109 denotes a recording device that records an output from the camera signal processing circuit 108 on a magnetic tape or the like.
[0035]
Reference numerals 110, 112, and 114 denote actuators for moving the variable power lens 102, the diaphragm 103, and the focus lens 105, respectively, and reference numerals 111, 113, and 115 drive actuators 110, 112, and 114, respectively, based on signals from a camera AF microcomputer 118 described later. Driver.
[0036]
A focus evaluation value processing circuit 116 extracts a high-frequency component used for focus detection from an output signal of the CCD 106, and an exposure evaluation 117 extracts an integrated value of luminance used for exposure control from an output signal of the image sensor 106. It is a value processing circuit. The focus evaluation value processing circuit 116 and the exposure evaluation value processing circuit 117 calculate the peak value and integration of the differential value from the video signal in one vertical scanning section of the video signal as shown in FIGS. The value is obtained and is used as the focus evaluation value.
[0037]
118 controls the overall operation of the entire system, controls the focus lens 105 based on the output signal of the focus evaluation value processing circuit 116, and controls the aperture 103 and the aperture 103 based on the output signal of the exposure evaluation value processing circuit 117. A camera AF microcomputer that controls the AGC 107.
Reference numeral 119 denotes a strobe for increasing the illuminance of the subject, reference numeral 120 denotes a main light emitting unit, and reference numeral 121 denotes an auxiliary light emitting unit.
[0038]
In the camera system of the present embodiment configured as shown in FIG. 1, the camera AF microcomputer 118 performs automatic focus adjustment by moving the focus lens 105 so that the output signal level of the focus evaluation value processing circuit 116 becomes maximum. Is going.
[0039]
Next, the control performed by the camera AF microcomputer 118 will be described in detail with reference to FIG. FIG. 3 is a flowchart illustrating a control procedure of the AF device according to the present embodiment, which is executed in the camera AF microcomputer 118.
[0040]
In FIG. 3, step 301 indicates the start of the process. The next step 302a is a process for lighting the auxiliary light emitting unit (flashing light emission) to prepare for operating the autofocus device.
[0041]
Next, in step 303a, a process of taking in a focus evaluation value is performed while the focus lens 105 is minutely driven.
In step 304a, based on the focus evaluation value captured in step 303a, it is determined whether or not the camera is currently in a focused state based on the result of the fine driving operation. If it is determined that the camera is in the focused state, the focus lens is stopped, and the process proceeds to a still image capturing routine from step 310a. If not in the focused state, the process proceeds to step 305a.
[0042]
In step 305a, it is determined in which direction the focal point is located, based on the result of the minute driving operation. If the direction in which the focal point is located can be determined, the process proceeds to step 306a, and a hill-climbing operation is performed in the determination direction. If it is not clear which direction the focal point is in, the process from step 303a is repeated.
[0043]
Step 307a is a step of determining whether or not the focus point, that is, whether or not the vertex of the focus evaluation value has been exceeded. If the result of this determination is that it does not exceed the vertex of the focus evaluation value, the process returns to step 306a to continue the hill-climbing process. If it has exceeded, the flow advances to step 308a and step 309a sequentially to return the focus lens to the top.
[0044]
By performing the processing in steps 308a and 309a, the focus lens can be controlled to the position where the focus evaluation value becomes the maximum. However, when the operation of returning to the vertex is performed, the subject changes due to panning or the like. In some cases, you may not know if the position is a true vertex.
[0045]
Therefore, when the focus lens reaches the vertex, the process returns to step 303a to confirm that the current position is the true vertex, that is, the in-focus point, and performs the fine driving operation again. I have.
[0046]
If it is determined in step 304a that the image is in focus, the process proceeds to a still image capturing routine from step 310a.
In step 310a, the movement of the focus lens is stopped. Next, in step 311a, the auxiliary light emitting unit is turned off. Next, in step 312a, the main light emitting section is turned on to increase the illuminance of the subject, and a still image is captured in that state. Then, after the capture of the still image is completed, the process proceeds to step 313a, and the focusing process is completed.
[0047]
Here, in the case of the imaging apparatus according to the present embodiment, the method of turning on the auxiliary light at the time of flashing the auxiliary light in step 302a and the processing performed in step 303a have the following significant features. ing.
[0048]
That is, as shown in (a), (b), and (c) of FIG. 5, the auxiliary light emitting unit 121 of the present embodiment synchronizes with the vertical scanning period of the video signal and sets the lighting time to the vertical scanning period. Light emission is performed at an integral multiple of the section. By performing such light emission, in intermittent light emission for improving the durability of the auxiliary light emitting unit 121, effective light emission can be performed in the vertical scanning section of all video signals, and light emission efficiency is greatly increased. Can be improved.
[0049]
In this embodiment, light emission is performed in synchronization with the vertical scanning section of the video signal, and two vertical scanning sections are turned on and one vertical scanning section is turned off. As a result, the illuminance becomes insufficient only once in three vertical scanning sections.
[0050]
However, if the evaluation value at that time is not used, AF control cannot be performed in the vertical scanning section, so that control is restricted and the control operation becomes complicated. Therefore, in the present embodiment, the average value of the AF evaluation values in the three vertical scanning sections is always obtained in step 303a, and the AF operation can be controlled constantly using the average value as the AF evaluation value. I have.
[0051]
By doing so, the AF evaluation value can always be obtained with the auxiliary light turned on in the two vertical scanning sections in any of the patterns (A), (B), and (C) of FIG. Can be performed, and the AF operation does not become complicated due to restrictions on control. As described above, by making the auxiliary light blink, the durability of the auxiliary light emitting unit 121 can be maintained. Also, by using the average value of the AF evaluation values in the three vertical scanning sections, accurate focus can always be obtained, so that the malfunction of the AF operation can be prevented.
[0052]
(Another embodiment of the present invention)
The present invention may be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) or an apparatus including one device.
[0053]
In addition, software for realizing the functions of the above-described embodiments is provided to an apparatus or a computer in a system connected to the various devices so as to operate various devices so as to realize the functions of the above-described embodiments. The present invention also includes a program code supplied and implemented by operating the various devices according to a program stored in a computer (CPU or MPU) of the system or the apparatus.
[0054]
In this case, the program code of the software implements the function of the above-described embodiment, and the program code itself and a unit for supplying the program code to the computer, for example, the program code is stored. The storage medium constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM and the like can be used.
[0055]
When the computer executes the supplied program code, not only the functions of the above-described embodiments are realized, but also the OS (operating system) or other application software running on the computer. It goes without saying that such a program code is also included in the embodiment of the present invention when the functions of the above-described embodiment are realized in cooperation with the above.
[0056]
Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, a CPU provided in the function expansion board or the function expansion unit based on the instruction of the program code. It is needless to say that the present invention also includes a case where the functions of the above-described embodiments are realized by performing part or all of the actual processing.
[0057]
【The invention's effect】
As described above, according to the present invention, when a predetermined high-frequency component of a video signal obtained from an imaging unit is extracted as a focus evaluation value and focus adjustment is performed so that the focus evaluation value is maximized, vertical synchronization is performed. In synchronization with a vertical scanning section including a retrace section that is a section for a signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and The lighting time is set to be twice as long as the vertical scanning section, and the light-off time of the light emitting means is set to the vertical scanning section. Therefore, effective light emission can be performed in all the vertical scanning sections. Therefore, it is possible to improve the durability of the auxiliary light emitting unit for automatic focus adjustment, and to significantly improve the light emission efficiency. In addition, power consumption can be reduced and automatic focus adjustment can be accurately performed.
[0058]
According to another feature of the present invention, a predetermined high-frequency component of a video signal obtained from an imaging unit is extracted as a focus evaluation value, and when performing focus adjustment so that the focus evaluation value is maximized, vertical synchronization is performed. In synchronization with a vertical scanning section including a blanking section that is a section for a signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and the light emitting unit is Focus adjustment is performed using the average focus evaluation value of the focus evaluation value when turned on and the focus evaluation value when not turned on, so that the durability of the auxiliary light emitting unit for automatic focus adjustment is improved. And accurate focus can always be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an embodiment of an imaging apparatus according to the present invention.
FIG. 2 is a characteristic diagram illustrating an AF evaluation value.
FIG. 3 is a flowchart illustrating an AF control operation of the automatic focusing apparatus according to the embodiment.
FIG. 4 is a diagram showing a vertical scanning section of a video signal.
FIG. 5 is a diagram showing lighting timing of auxiliary light according to the embodiment of the present invention.
FIG. 6 is a flowchart illustrating an AF control operation of the conventional automatic focusing device.
[Explanation of symbols]
101 Fixed first group lens 102 Magnifying lens 103 for zooming 103 Aperture 104 Fixed second group lens 105 Focus compensating lens 106 CCD
107 AGC
108 Camera signal processing circuit 109 Recording devices 110, 112, actuators 111, 113, 115 Driver 116 Focus evaluation value processing circuit 117 Exposure evaluation value processing circuit 118 Camera AF microcomputer 119 Strobe light 120 Main light emitting unit 121 Auxiliary light emitting unit

Claims (4)

An imaging apparatus that extracts a predetermined high-frequency component of a video signal obtained from an imaging unit as a focus evaluation value and performs focus adjustment so that the focus evaluation value is maximized.
In synchronization with a vertical scanning section including a retrace section that is a section for a vertical synchronization signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and the light emission is performed. An imaging apparatus, wherein a lighting time of the unit is twice as long as the vertical scanning section, and a light-off time of the light emitting unit is the vertical scanning section. An imaging apparatus that extracts a predetermined high-frequency component of a video signal obtained from an imaging unit as a focus evaluation value and performs focus adjustment so that the focus evaluation value is maximized.
In synchronization with a vertical scanning section including a retrace section that is a section for a vertical synchronization signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and the light emission is performed. An imaging apparatus characterized in that the focus is adjusted using an average focus evaluation value of a focus evaluation value when the means is turned on and a focus evaluation value when the means is not turned on. In the automatic focus adjustment method of extracting a predetermined high-frequency component of the video signal obtained from the imaging unit as a focus evaluation value and performing focus adjustment so that the focus evaluation value is maximized,
In synchronization with a vertical scanning section including a retrace section that is a section for a vertical synchronization signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and the light emission is performed. An automatic focus adjustment method, characterized in that a lighting time of the means is twice as long as the vertical scanning section, and a light-off time of the light emitting means is the vertical scanning section. In the automatic focus adjustment method of extracting a predetermined high-frequency component of the video signal obtained from the imaging unit as a focus evaluation value and performing focus adjustment so that the focus evaluation value is maximized,
In synchronization with a vertical scanning section including a retrace section that is a section for a vertical synchronization signal and a video section that is a section for a video signal, the light emitting unit is intermittently turned on during the focus adjustment operation, and the light emission is performed. An automatic focus adjustment method, wherein the focus is adjusted using an average focus evaluation value of a focus evaluation value when the unit is turned on and a focus evaluation value when the unit is not turned on.

Images