JP2006220729A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to widen a focusing range for movement of a subject even when an imaging apparatus capable of photographing a still image and a motion image does not drive a focus lens so as not to record AF drive noise when a motion image is photographed. <P>SOLUTION: The imaging apparatus includes: a range finding means for detecting a high frequency component in an image signal as a focal point evaluation value, then driving the focus lens based on the focal point evaluation value within a range set by a range setting means, and thus performing a focusing operation; a focus lens drive means for driving the focus lens based on the result of the range found by the range finding means; and a lens drive range limiting means for limiting the focus lens drive range of the focus lens drive means according to the range. When the range finding operation takes place right before a motion photographing, the lens drive range limiting means sets a limit so that the focus lens drive range is narrower than the above-described range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus that can capture a still image and a moving image and includes an automatic focus adjustment device.

  As an automatic focus adjustment device for a compact type electronic camera, focus adjustment is performed with the focus lens position where the high-frequency component (hereinafter referred to as a focus evaluation value) of the luminance signal of the subject image formed on the image sensor is maximized as the focus position. A contrast detection method (or hill climbing method) is generally performed. In addition to the still image shooting function, many compact type electronic cameras have a movie shooting function, but when adjusting the focus during movie shooting using the contrast detection method, the focus lens is driven during movie shooting. There is a need to. Focusing accuracy is one of the performances required for an autofocus device when taking a still image. However, when moving the focus lens repeatedly to increase the focusing accuracy when shooting one movie, the screen shakes. , It becomes an unstable video that feels strange when watching.

For example, Japanese Patent Application Laid-Open No. Hei 7-170438 discloses a method for performing a focus adjustment operation suitable for each of the moving image shooting mode and the still image shooting mode. Adjustments are being made.
JP-A-7-170438

  According to the above-mentioned JP-A-7-170438, it is possible to adjust the focus with high accuracy during still image shooting while ensuring follow-up to the movement of the subject during moving image shooting.

  However, in electronic cameras whose main purpose is still image shooting, the focus lens drive sound is relatively loud due to priority given to the focusing speed during still image shooting and to keep costs low. There are many. In such a camera with insufficient driving sound countermeasures, there arises a problem that the focus lens driving sound is recorded in the sound recording at the time of moving image shooting. On the other hand, it is possible to avoid recording drive sound by adjusting the focus immediately before shooting a movie and fixing the focus lens during movie shooting. There is an inferior problem.

  By the way, in an imaging apparatus capable of shooting a still image and a moving image, the recording size at the time of moving image shooting is generally smaller than that of a still image, for example, about VGA size. For subject images obtained from the same imaging lens, the recording size is reduced by processing such as addition readout and thinning readout in the imaging device, which corresponds to an increase in the permissible circle of confusion and a deeper depth of field. Become. Therefore, the blur is less noticeable during moving image shooting.

  Accordingly, an object of the present invention is to solve the above-described problems, and in the distance measurement operation immediately before moving image shooting, the focus lens drive range based on the distance measurement result is limited in consideration of the depth of field, thereby driving the focus lens. It is to improve the focusable range for the movement of the subject without recording the sound.

  In order to achieve the above object, the imaging apparatus according to claim 1 detects a high-frequency component in a video signal as a focus evaluation value, and based on the focus evaluation value in a distance measurement range set by a distance measurement range setting unit. A distance measuring means for driving the focus lens to perform a focusing operation, a focus lens driving means for driving the focus lens based on a distance measurement result of the distance measuring means, and the focus lens driving means according to the distance measurement range. Lens driving range limiting means for limiting the focus lens driving range, and the lens driving range limiting means limits the range to a range narrower than the distance measuring range when the distance measuring operation is immediately before moving image shooting. And

  In order to achieve the above object, an imaging apparatus camera according to claim 2 includes a depth-of-field detecting means for obtaining a depth of field from a focal length and an aperture value at the time of shooting, and a recording size of a still image or a moving image to be shot. A recording size setting unit for setting, and the lens driving range limiting unit sets a focus lens driving limiting range based on a depth of field obtained by the depth of field detection unit and a recording size set by the recording size setting unit. It is characterized by setting.

  According to the imaging apparatus of the present invention, it is possible to widen the focusable range with respect to the movement of the subject even when the focus lens is not driven so that AF driving sound is not recorded during moving image shooting.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an imaging apparatus to which an embodiment of the present invention is applied.

  Reference numeral 101 denotes a photographing lens including a zoom mechanism, 102 denotes an aperture and shutter for controlling the amount of light, 103 denotes an AE processing unit, 104 denotes a focus lens for focusing on an image sensor described later, 105 denotes an AF processing unit, and 106 denotes a strobe. , 107 is an EF processing unit, 108 is an image sensor as a light receiving unit or photoelectric conversion unit that converts reflected light from an object into an electric signal, 109 is a CDS circuit that removes output noise of the image sensor 108, and before A / D conversion A / D conversion unit including a non-linear amplification circuit, 110 is an image processing unit, 111 is a WB processing unit, 112 is a format conversion unit, 113 is a high-speed built-in memory (for example, random access memory, hereinafter referred to as DRAM), Reference numeral 114 denotes an image recording unit including a recording medium such as a memory card and its interface, and 115 denotes a photographing sequence. A system control unit for controlling the system, etc., 116 is an image display memory (hereinafter referred to as VRAM), 117 is an image display and a display for assisting operation, a status display of the imaging device, and a shooting screen and a distance measurement area at the time of shooting , An operation display unit 118 for operating the imaging apparatus from the outside, 119 a sensor as detection means for detecting the attitude of the imaging apparatus, 120 a main switch for powering on the system, 121 Is a shooting mode switch for setting a still image or moving image shooting mode, 122 is a switch for performing a shooting standby operation such as AF or AE (hereinafter referred to as SW1), and 123 is a shooting switch for performing shooting after operation of SW1 ( (Hereinafter referred to as SW2).

  The DRAM 113 is used as a high-speed buffer as temporary image storage means, or a working memory for image compression / decompression. The operation unit 118 includes, for example, the following. Menu switch for performing various settings such as the shooting function of the imaging device and settings for image playback, a zoom lever (zoom instruction means) for instructing the zoom operation of the taking lens, an operation mode switch between the shooting mode and the playback mode, and a still image A recording size setting switch (recording size setting means) for setting a recording size of an image or a moving image, a switch (ranging range setting means) for setting a distance measurement range such as a distant view or a macro mode, and the like.

  The operation of the embodiment of the present invention will be described in detail below with reference to FIG. FIG. 2 is a flowchart showing the operation of the image pickup apparatus to which the embodiment of the present invention is applied.

  First, the state of the main switch 120 is detected in step S201, and if it is ON, the process proceeds to step S202. Here, the function of the main switch 120 is to turn on the system. In step S202, the remaining capacity of the image recording unit 114 is checked. If the remaining capacity is 0, the process proceeds to step S203, and if not, the process proceeds to step S204. In step S203, a warning is given that the remaining capacity of the image recording unit 114 is 0, and the process returns to step S201. The warning may be displayed on the operation display unit 117, a warning sound may be output from a sound output unit (not shown), or both may be performed.

  In step S204, the zoom operation is performed according to the flowchart of FIG. In step S205, the state of the switch SW1 is checked. If it is ON, the process proceeds to step S207, and if not, the process proceeds to step S206. Here, the function of SW1 is to perform a shooting standby operation such as AF or AE. In step S206, the state of the main switch 120 is checked. If it is ON, the process proceeds to step S204, and if not, the process proceeds to step S201. In step S207, the AE processing unit 103 performs AE processing from the output of the image processing unit 110.

  In step S208, an AF operation is performed according to the flowchart of FIG. In step S209, the state of SW2 is checked. If ON, the process proceeds to step S211; otherwise, the process proceeds to step S210. Here, the function of SW2 is to perform photographing after operation of SW1. In step S210, the state of SW1 is checked. If ON, the process returns to step S209. Otherwise, the process returns to step S204. In step S211, a photographing operation is performed according to the flowchart of FIG. In step S212, the remaining capacity of the image recording unit 114 is checked. If the remaining capacity is 0, the process proceeds to step S203, and if not, the process proceeds to step S213. In step S213, the state of SW2 is checked, and if not ON, the process proceeds to step S210.

  The zoom operation subroutine of S204 in the flowchart of FIG. 2 will be described below with reference to the flowchart of FIG. FIG. 3 is a flowchart of the subroutine of the zoom operation (S204) in the flowchart of FIG.

  In step S301, it is checked whether a zoom lever (not shown in FIG. 1) is operated to the Tele side. If it is ON, the process proceeds to step S302; otherwise, the process proceeds to step S306. In step S302, it is checked whether the zoom position is at the tele end. If it is not the tele end, the process proceeds to step S303, and if it is the tele end, the process proceeds to step S304. In step S303, the zoom position is moved to the Tele side, and the process returns to step S301. In step S304, it is checked whether the electronic zoom is used and the maximum magnification is reached. If it is the maximum magnification, the process proceeds to step S306, and if not, the process proceeds to step S305. In step S305, the electronic zoom magnification is increased and the process returns to step S301.

  In step S306, it is checked whether a zoom lever (not shown in FIG. 1) is operated to the Wide side. If it is ON, the process proceeds to step S307; otherwise, the process proceeds to step S311. In step S307, it is checked whether the zoom position is at the wide end. If it is not the wide end, the process proceeds to step S308, and if it is the wide end, the process proceeds to step S311. In step S308, it is checked whether the electronic zoom is used. If so, the process proceeds to step S309, and if not, the process proceeds to step S310. In step S309, the magnification of the electronic zoom is lowered and the process returns to step S306. In step S310, the zoom position is moved to the Wide side, and the process returns to step S306. In step S311, the current zoom position is stored in a calculation memory (not shown) built in the system control unit 115.

  Hereinafter, the AF operation subroutine of step S208 in the flowchart of FIG. 2 will be described with reference to the flowchart of FIG. The AF operation is performed by detecting a peak of a focus evaluation value that is a high frequency component of a signal obtained from the image sensor. FIG. 4 is a flowchart of the subroutine of the AF operation (step S208) in the flowchart of FIG.

  First, in step S401, the focus lens 104 is moved to the scan start position. Here, the scan start position is set to an infinite end in the distance measurement range. In step S402, the focus evaluation value and the position of the focus lens 104 are stored in a calculation memory (not shown) built in the system control unit 115. When the position of the focus lens 104 is driven by a stepping motor, it is detected as a relative position from the reset position by a photo interrupter (not shown in FIG. 1). In step S403, it is checked whether or not the lens position is at the scan end position. If it is the end position, the process proceeds to step S405. If not, the process proceeds to step S404. Here, the scan end position is set to the closest end in the distance measurement range. In step S404, the focus lens 104 is driven and moved in the closest direction by a predetermined amount. In step S405, a maximum value equal to or larger than a predetermined value in the focus evaluation values stored in step S402 is obtained, and the position of the focus lens 104 at that time is extracted.

  In step S406, it is checked whether still image shooting or moving image shooting is performed. If still image shooting is performed, the process proceeds to step S410, and if moving image shooting is performed, the process proceeds to step S407.

  In step S407, the in-focus position driving range is calculated according to the flowchart of FIG.

  In step S408, it is checked whether or not the position of the focus lens 104 extracted in step S405 is within the focus position drive range obtained in step S407. If it is within the focus position drive range, the process proceeds to step S410. If so, the process proceeds to step S409. In step S409, it is checked whether the position of the focus lens 104 extracted in step S405 is located on the far side or the near side with respect to the focus position drive range. The focus lens 104 is moved to the farthest end position when it is located on the farthest end position.

  In step S410, the focus lens 104 is moved to a position where the focus evaluation value shows the maximum value. Here, in step S405, when the maximum focus evaluation value equal to or greater than the predetermined value is not obtained, that is, when out of focus, the focus lens 104 is moved to a preset position called a fixed point.

  Hereinafter, a subroutine for calculating the focus position drive range (focus lens drive limit range) in S407 in the flowchart of FIG. 4 will be described with reference to the flowchart of FIG. FIG. 5 is a flowchart of the focus position drive range calculation (S407) subroutine in the flowchart of FIG. 4, and an explanatory diagram showing the relationship between the scan range and the focus position drive range.

  First, in step S501, the current zoom position stored in step S311 in FIG. 3 is checked to determine the focal length. The relationship between the zoom position and the focal length is stored in a calculation memory (not shown) built in the system control unit 115. In step S502, the aperture value of the aperture 102 is checked. In step S503, the recording size set by the recording size setting means is checked. In step S504, the depth of field is obtained from the obtained focal length and aperture value, and an amount obtained by multiplying the coefficient corresponding to the set recording size is subtracted from both ends on the far side and near side of the distance measuring area. This range is set as the focus position drive range. Since the permissible circle of confusion can be considered larger as the set recording size is smaller, the focus position drive range is set narrower.

  At both ends of the focus position drive range set in this way, both ends of the distance measurement area are located in a range where blur is small due to the depth of field and can be regarded as in focus. It is possible to widen the focusable range.

  Hereinafter, the subroutine of the photographing operation in step S211 in the flowchart of FIG. 2 will be described with reference to the flowchart of FIG. FIG. 6 is a flowchart of the subroutine of the photographing operation (step S211) in the flowchart of FIG.

  First, in step S601, it is checked whether still image shooting or moving image shooting is performed. If still image shooting is performed, the process proceeds to step S602, and if moving image shooting is performed, the process proceeds to step S609.

  In step S602, preparation for still image shooting such as drive switching of the image sensor is performed. In step S603, the subject brightness is measured. In step S604, the image sensor 108 is exposed according to the subject brightness measured in step S603. The image formed on the image sensor surface is photoelectrically converted into an analog signal, which is sent to the A / D converter 109 in step S605, and after preprocessing such as output noise removal and nonlinear processing of the image sensor 108. Converted to a digital signal. In step S606, the output signal from the A / D conversion unit 109 is white balance adjusted by the image processing unit 110 by the WB processing unit 111 to obtain an appropriate output image signal. In step S <b> 607, the output image signal is converted into an image format such as a JPEG format by the format conversion unit 112 and temporarily stored in the DRAM 113. In step S608, the data in the DRAM 113 is transferred and stored in the image recording unit 114 to an external storage medium such as a memory in the camera or a memory card attached to the camera.

  In step S609, preparation for moving image shooting such as drive switching of the image sensor is performed. In step S610, the subject brightness is measured. In step S611, video recording starts. As processing during recording, processing similar to processing for still images, such as exposure, A / D conversion, image processing, format conversion, and transfer to a recording medium, is performed at a cycle of a frame rate of, for example, 30 fps. In step S612, the state of SW2 is checked. If ON, the process proceeds to step S614, and if not, the process proceeds to step S613. During recording, the DRAM 113 mainly functions as a buffer memory, and data in the DRAM 113 is recorded on a storage medium by the image recording unit 114. If the transfer speed of the recording medium is low, the DRAM 113 exceeds the processing capacity. It becomes impossible to continue recording. Also, recording cannot be continued even when the remaining capacity of the recording medium runs out. In order to avoid the above situation, in step S613, the remaining capacity of the DRAM 113 and the recording medium and the transfer status to the recording medium are confirmed. If the transfer is OK, the process proceeds to step S611, otherwise the process proceeds to step S614. . In step S614, the recording is finished, and it is confirmed that the data in the DRAM 113 is transferred to the recording medium and the saving process is finished.

  As described above, according to the imaging apparatus of the present invention, it is possible to expand the focusable range for the movement of the subject even when the focus lens is not driven so that the AF driving sound is not recorded during moving image shooting. Become.

It is a block diagram which shows the structure of the imaging device to which this invention is applied. It is a flowchart figure showing operation | movement of the imaging device to which this invention is applied. FIG. 3 is a flowchart of a zoom operation subroutine in FIG. 2. FIG. 3 is a flowchart of an AF operation subroutine in FIG. 2. FIG. 5 is a flowchart and an explanatory diagram of a sub-routine of a focus position driving range (focus lens driving limit range) in FIG. 4. FIG. 3 is a flowchart of a shooting operation subroutine in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Fixed lens 102 Aperture and shutter 103 AE processing part 104 Focus lens part 105 AF processing part 106 Strobe 107 EF processing part 108 Image sensor 109 A / D conversion part 110 Image processing part 111 WB processing part 112 Format conversion part 113 DRAM
114 Image recording unit 115 System control unit 116 VRAM
117 Operation Display Unit 118 Operation Unit 119 Attitude Detection Sensor 120 Main Switch 121 Mode Switch 122 Switch 123 Shooting Switch

Claims (2)

A distance measuring unit that detects a high frequency component in the video signal as a focus evaluation value, and performs a focusing operation by driving a focus lens based on the focus evaluation value in a distance measurement range set by the distance measurement range setting unit; A focus lens driving unit that drives a focus lens based on a distance measurement result of the distance measuring unit; and a lens driving range limiting unit that limits a focus lens driving range of the focus lens driving unit according to the distance measuring range. ,
The imaging apparatus capable of shooting a still image and a moving image, wherein the lens driving range limiting means restricts the range to a range narrower than the distance measuring range in a distance measuring operation immediately before moving image shooting. A depth-of-field detecting means for obtaining a depth of field from a focal length and an aperture value at the time of shooting, and a recording size setting means for setting a recording size of a still image or a moving image to be shot;
2. The lens driving range limiting unit sets a focus lens driving limiting range based on a depth of field obtained by the depth of field detecting unit and a recording size set by the recording size setting unit. The imaging device described.

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