JP2009258338A - Automatic focusing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve focusing accuracy for a subject. <P>SOLUTION: A digital camera 1 includes: an optical system 11 which forms a subject image; a diaphragm 40 which adjusts the quantity of light passing through the optical system 11; a CCD image sensor 12 which images the subject image formed by the optical system 11, to produce image data; a controller 17 which controls the optical system 11, so as to adjust a focusing state with respect to the image data in a focusing region 60 being a part of the image data produced by the CCD image sensor 12; and a controller 17 which makes the size of the focusing region 60 variable according to the adjustment state of the diaphragm 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an automatic focusing apparatus capable of adjusting a focusing state with respect to image data in a focusing area.

  As a conventional automatic focusing device, there is one as described in Patent Document 1 below.

This automatic focusing device is intended to achieve automatic focusing (AF) more accurately. The automatic focusing apparatus includes a focusing unit that performs focusing within the distance measurement frame, a setting unit that sets the distance measurement frame to a point where the user is gazing, and a size of the set distance measurement frame. Control means for controlling the height according to the focal length.
JP-A-5-110925

  By the way, in the general automatic focusing device, the size of the focusing area is fixed. If the size of the focusing area is fixed in this way, there is a case where the subject cannot be focused accurately.

  For example, as shown in the left diagram of FIG. 8, when shooting a person, the aperture is often opened. In this case, the depth of field is shallow. Therefore, when the focus area is large with respect to the subject (person), a perspective difference (such as a person and a background) occurs in the focus area. This perspective difference becomes a distance measurement error when focusing, and it is impossible to focus accurately.

  On the other hand, as shown in the diagram on the right side of FIG. In this case, the depth of field is deep. In such a case, if the size of the focus area is small with respect to the image data acquired by the imaging means, the focus state of the subject can be adjusted, but a high-contrast portion cannot be picked up from the image data. The focus state is adjusted based on the low contrast portion. That is, the in-focus state cannot be adjusted in consideration of a high contrast portion.

  Accordingly, an object of the present invention is to improve the focusing accuracy for a subject in order to solve the above-described problems.

  An automatic focusing apparatus according to the present invention includes an optical system that forms a subject image, a diaphragm that adjusts the amount of light passing through the optical system, and an imaging unit that captures the formed subject image and generates image data. A focusing means for controlling the optical system so as to adjust a focus state based on image data in a focus area that is a part of the generated image data, and an adjustment state of the diaphragm, And an area adjusting means for making the size of the focusing area variable.

  In this way, the size of the focus area can be made variable according to the adjustment state of the diaphragm.

  Preferably, the area adjustment unit adjusts the size of the in-focus area to be smaller as the amount of light passing through the optical system increases in accordance with the adjustment of the diaphragm.

  In this way, when the aperture is open, the focusing area can be reduced. Therefore, for example, the in-focus state can be adjusted by aligning the in-focus area with the eyes of the person (left in FIG. 9). As a result, distance measurement errors can be reduced. On the other hand, when the aperture is reduced, the focusing area can be enlarged. For this reason, for example, the in-focus state can be adjusted by aligning the in-focus area with the majority of the landscape (right in FIG. 9). Thereby, for example, an object with high contrast can be picked up in a landscape, and focusing accuracy can be improved.

  Preferably, it further comprises a number adjusting means for making the number of the focusing areas variable according to the adjustment state of the diaphragm.

  Preferably, the number adjusting means adjusts so that the number of in-focus areas increases as the amount of light passing through the optical system increases in accordance with the adjustment of the diaphragm.

  In this way, when the aperture is open, the number of focusing areas can be increased. Thereby, focusing can be performed with higher accuracy in an environment where the depth of field is shallow.

  The present invention can focus on a subject with higher accuracy even when the depth of field changes.

(Embodiment 1)
1. Configuration Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1-1 Overview of Overall Configuration FIG. 1 is a perspective view of a digital camera 1 according to the present embodiment. FIG. 2 is a block diagram showing a configuration of the digital camera 1 according to the present embodiment. The configuration will be specifically described below.

  The optical system 11 collects optical signals from the subject and forms a subject image on the CCD image sensor 12. The optical system 11 includes an objective lens 111, a zoom lens 112, and a focus lens 113.

  The zoom lens 112 is driven by the zoom driving unit 115 and adjusts the range (view angle) in which the subject image is captured. That is, the zoom lens 112 can adjust the focal length. The focus lens 113 is driven by the focus drive unit 116 to adjust the focus. The zoom drive unit 115 includes a cam mechanism for moving the zoom lens 112 and an actuator for driving the cam mechanism, and drives the zoom lens 112 in accordance with control from the controller 17. The focus driving unit 116 includes a cam mechanism for moving the focus lens 113 and an actuator for driving the cam mechanism, and drives the focus lens 113 in accordance with control from the controller 17.

  The diaphragm 40 is composed of five blades and adjusts the amount of light passing through the optical system 11. The diaphragm 40 is driven by a diaphragm driver 41. The diaphragm drive unit 41 is configured to include a cam mechanism, an actuator for driving the cam mechanism, and the like, and drives the diaphragm 40 in accordance with control from the controller 17.

  The shutter 50 is opened or closed to adjust the amount of light hitting the CCD image sensor 12 with time. The shutter 50 is driven by an aperture driving unit 51. The shutter drive unit 51 includes a cam mechanism and an actuator for driving the cam mechanism, and drives the shutter 50 in accordance with control from the controller 17.

  The CCD image sensor 12 is an imaging unit that captures a subject image formed by the optical system 11 and generates image data. The CCD image sensor 12 captures a subject image based on the pulse signal supplied from the timing generator 121 and generates image data. The timing generator 121 is configured by an integrated circuit such as an LSI and supplies a pulse signal to the CCD image sensor 12. Here, the pulse signal that the timing generator 121 supplies to the CCD image sensor 12 supplies, for example, 30 frame readout pulse signals per second. As a result, the CCD image sensor 12 can acquire image data of a frame every 1/30 second.

  The AD converter 13 converts the image data generated by the CCD image sensor 12 into digital data.

  The image processing unit 14 performs predetermined processing on the image data converted into digital data. As the predetermined processing, gamma conversion, YC conversion, electronic zoom processing, compression processing, expansion processing, and the like can be considered, but are not limited thereto.

  The buffer memory 15 functions as a work memory when the image processing unit 14 performs image processing and when the controller 17 performs control processing. The buffer memory 15 can be realized by, for example, a DRAM.

  The flash memory 16 is used as a built-in memory. The flash memory 16 can store a program for controlling the controller 17, a setting value, and the like in addition to the image data obtained by performing image processing on the image data.

  The controller 17 is a control means for controlling the entire digital camera 1. The controller 17 may be realized by a microcomputer or a hard-wired circuit. In short, the control means of the present invention only needs to be able to control the own device. Various controls of the controller 17 will be described later.

  The card slot 18 is a slot for inserting and removing the memory card 19. The card slot 18 may have a function of controlling the memory card 19. The memory card 19 includes a flash memory or the like. The memory card 19 can store the image data image-processed by the image processing unit 14.

  The liquid crystal monitor 20 is display means for displaying image data and various settings of the digital camera 1. As the display means of the present invention, an organic EL display or the like can be used instead of the liquid crystal monitor.

  The shutter switch 21 is provided on the upper surface of the digital camera 1 and can detect half-press and full-press from the user. When a half-press or full-press operation is performed by the user, the shutter switch 21 outputs an operation signal corresponding to the operation to the controller 17. That is, the shutter switch 21 is configured to receive a focus instruction.

  The cross button 22 is provided on the back of the digital camera 1 so that various parameters of the digital camera 1 can be manually adjusted. For example, the aperture value of the aperture can be set. In this case, when the key below the cross button is pressed, the controller 17 displays a screen as shown in FIG. Then, the user selects the aperture value by pressing the left and right keys of the cross button 22 and determines with the keys on the cross button 22. Thus, the controller 17 receives the determined aperture value. At this time, the controller 17 stores the received aperture value in the buffer memory 15 as the currently set aperture value. Then, the controller 17 adjusts the aperture 40 via the aperture drive unit 41 based on this aperture value.

  In this embodiment, the aperture value is manually set and the aperture is adjusted. However, the present invention is not limited to this. For example, the brightness around the digital camera 1 may be measured, and the aperture may be adjusted based on the result. Since this technique is a conventional exposure control technique, a description thereof will be omitted. Further, it may be set by operating a dial button or the like as in a general single-lens reflex digital camera.

1-2 Description of Control of Controller 17 in the Present Embodiment The controller 17 in the present embodiment performs focus control and area adjustment control. That is, in the first embodiment, the controller 17 is a focusing unit and a region adjusting unit.

  The controller 17 that realizes the focusing means controls the optical system 11 so as to adjust the focusing state with respect to the image data in the focusing area that is a part of the image data generated by the CCD image sensor 12. Note that the focusing area in the present embodiment is provided at the center of the image data. However, this is an example, and the in-focus area may be moved in the image data by a user operation.

  The controller 17 that realizes the area adjustment means makes the size of the focus area variable according to the adjustment state of the diaphragm 40. Then, the controller 17 adjusts so that the size of the in-focus area decreases as the amount of light passing through the optical system 11 increases in accordance with the adjustment of the diaphragm 40.

  Hereinafter, each control will be specifically described.

1-2-1. Focus Control The controller 17 controls the optical system 11 in order to adjust the focus state of the subject image in the tracking area imaged by the CCD image sensor 12. The controller 17 in the present embodiment performs the following processing to control the in-focus state. The controller 17 adjusts the in-focus state by hill-climbing (contrast) autofocus means.

  The controller 17 operates the focus lens 113 within a preset operating range of the focus lens 113. Accordingly, the controller 17 continuously acquires image data from the image processing unit 14. Then, the controller 17 analyzes the image data (in-focus area) continuously input from the image processing unit 14. At this time, the controller 17 calculates the sharpness, which is a degree representing the clarity of the boundary of the image and the depiction ability of a fine portion, with respect to the input image. Then, the controller 17 selects an image having the maximum sharpness from among the images that are made continuous. Next, the controller 17 detects the position of the focus lens 113 from which the selected image can be acquired, and determines the amount of movement of the focus lens 113 based on the current position of the focus lens 113. When the movement amount of the focus lens 113 is determined, a signal including the movement amount is output to the focus lens driving unit 116 in order to move the focus lens 113. Any method may be used to detect the current position of the focus lens 113. Preferably, a position sensor is provided in the focus lens 113, and the current position of the focus lens 113 in the optical system 11 is detected. The current position information may be output to the controller 17.

1-2-2 Area Adjustment Control The controller 17 adjusts the size of the focusing area 60 based on the F value in which the diaphragm 40 is adjusted. For example, as shown in FIG. 4, when the aperture is set to the open side (for example, F3.5), the controller 17 reduces the size of the focusing area 60 with respect to the screen. Further, when the aperture is set on the aperture side (for example, F4.4), the size of the focusing area 60 is increased with respect to the screen. Note that just because the aperture is adjusted to the open side does not necessarily mean that the in-focus area has to be enlarged. For example, when the aperture value is F4.0 and the aperture value is F4.4, the size of the focus area is adjusted to the same size, and when the aperture value is F3.5, the size of the focus area is set to the aperture value F4. It may be made smaller than 0.0. Here, the F value (aperture value) used by the controller 17 can be dealt with by reading the data stored in the buffer memory 15. However, the present invention is not limited to this, and the controller 17 may receive an aperture value from the aperture drive unit 41 and respond accordingly. In this case, the aperture drive unit can output the aperture value by storing the aperture value or detecting the aperture state (aperture value).

  In the present embodiment, the size of the focus area is adjusted in accordance with the adjustment state of the diaphragm. However, the present invention is not limited to this, and the controller 17 may adjust the number of in-focus areas 60a in accordance with the diaphragm adjustment state. For example, as shown in the left diagram of FIG. 5, when the aperture value is set to F3.5 from the state where the aperture value is set to F4.0, the number of in-focus areas 60a is increased to nine. In this way, in the environment where the depth of field is shallow, a plurality of in-focus areas are provided, so that in-focus can be achieved with higher accuracy. In this case, the controller 17 is a number adjusting unit that makes the number of in-focus areas variable according to the aperture adjustment state.

2. Operation Next, the automatic focusing operation of the digital camera 1 configured as described above will be described with reference to the flowchart of FIG. In the present embodiment, the digital camera 1 will be described in a state where the still image shooting mode is set. In the still image shooting mode, a still image can be shot by the digital camera 1. The operation will be described below.

  In the still image shooting mode, the focusing operation and the shooting operation are performed in parallel.

  First, the focusing operation will be described. The controller 17 determines whether or not the shutter switch 21 has received a half-press operation from the user (S1). The process of step S1 is repeated until the user presses the shutter switch 21 halfway. In the present embodiment, the aperture value is set by the cross button 22 before the shutter switch 21 accepts the half-press operation.

  When the shutter switch 21 accepts the half-press operation, the controller 17 reads the aperture value from the buffer memory 15 (S2). If the aperture value is not stored in the buffer memory 15, the aperture value is acquired from the aperture drive unit 41. If the aperture value is read out from the buffer memory 15 in this way, the aperture value can be easily obtained as compared with the case where the aperture value is acquired from the aperture drive unit 41, so that the processing time can be shortened.

  And the controller 17 adjusts the magnitude | size of the focusing area | region 60 based on the acquired aperture value (S3). Thereafter, the controller 17 adjusts the in-focus state for the image data in the adjusted in-focus area 60 (S4).

  Thereby, the size of the focus area can be adjusted according to the adjustment state of the diaphragm. Further, the focus state can be adjusted based on the adjusted focus area.

  Next, the photographing operation will be described.

  The controller 17 determines whether or not the shutter switch 21 has received a full-press operation from the user (T1). The process of step T1 is repeated until the user fully presses the shutter switch 21.

  When the shutter switch 21 receives the full-press operation, the controller 17 captures a subject image (T2). The shooting operation will be briefly described. First, the controller 17 controls the CCD image sensor 12 to capture a subject image. The image data generated by the CCD image sensor 12 is input to the controller 17 via an AD converter and an image processing unit. Thereafter, the controller 17 stores this image data in the memory card 19.

3. Summary As described above, the digital camera 1 of the present embodiment includes the optical system 11 that forms a subject image, the diaphragm 40 that adjusts the amount of light passing through the optical system 11, and the subject image formed by the optical system 11. Optical image so as to adjust the in-focus state with respect to the image data in the focusing area 60 which is a part of the image data generated by the CCD image sensor 12 A controller 17 that controls the system 11 and a controller 17 that makes the size of the focusing area 60 variable according to the adjustment state of the diaphragm 40 are provided.

  In this way, the size of the focus area can be made variable according to the adjustment state of the diaphragm.

(Other embodiments)
Embodiment 1 was illustrated as embodiment of this invention. However, the present invention is not limited to the first embodiment, and can be implemented in other embodiments. Therefore, other embodiments of the present invention will be described collectively below.

  In the first embodiment of the present invention, the CCD image sensor 12 is exemplified as the imaging means. However, other imaging means may be used instead of the CCD image sensor 12. As another imaging means, for example, a CMOS image sensor or the like may be used. By using a CMOS image sensor, power consumption can be reduced. In other words, the image pickup means picks up a subject image and generates image data. If a CMOS image sensor is used instead of the CCD image sensor, noise on the image data output from the imaging means can be reduced.

  In the first embodiment of the present invention, the pulse signal supplied from the timing generator 121 to the CCD image sensor 12 is configured to supply, for example, 30 frame readout pulse signals per second. I can't. For example, the pulse signal may be supplied 50 times or 60 times per second. In short, the timing generator only needs to be able to supply a pulse signal for frame reading.

  In Embodiment 1 of the present invention, the aperture value can be set before step S1, but the present invention is not limited to this.

  In the first embodiment of the present invention, the operation of adjusting the size of the in-focus area based on the manually set aperture value has been described. However, for example, the following method can be considered as another embodiment. This is to adjust the size of the focusing area based on the aperture value automatically set by the digital camera. In this case, for example, after the shutter switch accepts half-pressing in step S1 in FIG. 5, exposure control such as an aperture value is performed. In this way, the aperture value set in the exposure control can be acquired in step S2. Thereby, the size of the focus area can be adjusted based on the automatically set aperture value.

  In the first embodiment of the present invention, as shown in FIG. 6, the size of the in-focus area is adjusted when the shutter switch is half-pressed, but the present invention is not limited to this. For example, as shown in FIG. 6, when the aperture adjustment is changed, the size of the focus area may be adjusted. Hereinafter, the focusing operation will be specifically described.

  First, when the still image shooting mode is set, the controller 17 acquires an aperture value as in step S2 (U1). And the controller 17 adjusts the focusing area | region 60 based on the acquired aperture value like step S3 (U2).

  Then, the controller 17 determines whether or not the aperture adjustment has been changed (U3). If the aperture adjustment has been changed, the process proceeds to step U1. On the other hand, if the aperture adjustment has not been changed, the controller 17 determines whether or not the shutter switch has received a half-press signal as in step S1 (U4). If the shutter switch has not accepted the half-press operation, the process proceeds to step U3. On the other hand, when the shutter switch accepts a half-press operation, the controller 17 performs focusing control as in step S4 (U5).

  This makes it possible to adjust the size of the focus area when the aperture adjustment is changed.

  That is, the present invention is not limited to the above-described embodiment, and can be implemented in various modes.

  The present invention can be applied to an automatic focusing device that can automatically focus on image data in a focusing area. Specifically, it can be used for digital cameras, movies, mobile terminals with cameras, and the like.

1 is a perspective view of a digital camera according to an embodiment of the present invention. The block diagram which shows the structure of the digital camera concerning embodiment of this invention The figure for demonstrating an example of the setting screen of the aperture | diaphragm | restriction concerning Embodiment 1 of this invention. The figure for demonstrating adjustment of the magnitude | size of a focus area | region according to the adjustment state of the aperture_diaphragm | restriction concerning Embodiment 1 of this invention. The figure for demonstrating adjustment of the number of focusing area | regions according to the adjustment state of the aperture_diaphragm | restriction of other embodiment. 1 is a flowchart for explaining an operation example of the digital camera according to the first embodiment of the present invention. Flowchart for explaining an operation example of a digital camera according to another embodiment A diagram for explaining a conventional problem The figure for demonstrating the usage example of the digital camera in embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 11 Optical system 112 Zoom lens 113 Focus lens 115 Zoom drive part 116 Focus drive part 12 CCD image sensor 121 Timing generator 13 AD converter 14 Image processing part 15 Buffer memory 17 Controller 19 Memory card 20 Liquid crystal monitor 21 Shutter switch 40 Aperture 41 Aperture Drive Unit 50 Shutter 51 Shutter Drive Unit 60, 60a Focusing Area

Claims (4)

An optical system for forming a subject image;
A diaphragm for adjusting the amount of light passing through the optical system;
Imaging means for capturing the formed subject image and generating image data;
Focusing means for controlling the optical system so as to adjust a focusing state based on image data in a focusing area that is a part of the generated image data;
An area adjusting means for changing a size of the in-focus area according to an adjustment state of the diaphragm;
An automatic focusing device comprising: The region adjusting means includes
As the amount of light passing through the optical system increases in accordance with the adjustment of the diaphragm,
Adjusting the size of the in-focus area to be small,
The automatic focusing device according to claim 1. In accordance with the adjustment state of the diaphragm, further comprising a number adjusting means for changing the number of the focus areas.
The automatic focusing device according to claim 1. The number adjusting means is
As the amount of light passing through the optical system increases in accordance with the adjustment of the diaphragm,
Adjust the number of in-focus areas to be large,
The automatic focusing device according to claim 3.

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