JP2010021846A - Image capturing apparatus and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform auto-focusing with a higher degree of precision. <P>SOLUTION: A drive control part 3 allows an image sensor 2 to output image capturing signals in a first mode to output image capturing signals corresponding to a predetermined number of pixels of all pixels in the image sensor 2. A lens drive control part 5 performs auto-focus control based on the image capturing signals output by the image sensor 2 in the first mode. A face detection part 8 determines an area where feature portions of a subject image are imaged from an image based on the image capturing signal output by the image sensor 2 in the first mode. The drive control part 3 allows the image sensor 2 to output the image capturing signals in a second mode to output the image capturing signals corresponding to the image for the area detected by the face detection part 8. The lens drive control part 5 performs auto-focus control based on the image capturing signals output by the image sensor 2 in the second mode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that captures an image and a program for controlling the operation of the imaging apparatus.

  The digital camera has a display unit such as a liquid crystal display. In addition, the display unit updates and displays a live view image for preview before the main shooting at a predetermined time interval. Such image display for preview (preview display) at the time of photographing with a digital camera is very useful for grasping the photographing state of the subject.

  As an autofocus control method, there is a hill-climbing method that uses an image signal from an image sensor. The hill-climbing method is a focusing control method in which the lens position where the evaluation value for focusing such as the contrast of the image by the image sensor becomes the largest is the focusing position. This hill-climbing method has the advantage that it is not necessary to provide a distance measuring sensor for measuring the distance to the subject, and is therefore used in many digital cameras.

The image sensor reads a relatively wide area for live view display, and the autofocus readout reads a part of the area in order to realize high speed. In such a technique, there is one described in Patent Document 1 below. In this prior art, after image data of all imaging areas of the image sensor is once stored in a memory, image data of a narrow area is cut out from the image data of all the imaging areas, and autofocus processing is performed based on the image data of the cut out area. Do.
Japanese Patent Laid-Open No. 2002-23049

  However, in the technique described in Patent Document 1, autofocus is performed using image data obtained by cutting out a central portion of image data in a wide area. As a result, when the feature portion of the subject exists in a place other than the central portion of the image data of the wide area, the feature portion of the subject is not always in focus. Therefore, there is a problem that the accuracy of autofocus is lowered.

  The present invention has been made to solve the above-described problems, and provides an imaging apparatus capable of performing autofocus with higher accuracy.

  The present invention relates to an imaging device that generates an imaging signal by photoelectrically converting a subject image formed by an imaging optical system using a plurality of pixels, and drive control that controls an operation of the imaging device outputting the imaging signal. A focus control unit that performs autofocus control, and a detection unit that detects a region in which a characteristic part of the subject image is captured from an image based on the imaging signal, and the drive control unit includes: In the first mode in which the imaging signal corresponding to a predetermined number of pixels among all the pixels in the imaging device is output, the imaging device is configured to output the imaging signal, and the focus control unit is configured to output the imaging signal from the imaging device. Autofocus control is performed based on the imaging signal output in the first mode, and the detection unit is an image based on the imaging signal output by the imaging element in the first mode. In the second mode, the area in which the characteristic part of the subject image is captured is detected, and the drive control unit further outputs the imaging signal corresponding to the image of the area detected by the detection unit. The imaging apparatus is characterized in that the imaging signal is output to an element, and the focus control unit further performs autofocus control based on the imaging signal output by the imaging element in the second mode.

  In the imaging apparatus of the present invention, when the subject image is a human image, the detection unit determines an area where the face portion of the subject image is captured.

  In the imaging device of the present invention, the imaging device outputs the imaging signal at a high frame rate in the second mode as compared with the first mode.

  The present invention also provides a program for controlling the operation of an image pickup apparatus including an image pickup device that generates an image pickup signal by photoelectrically converting a subject image formed by an image pickup optical system using a plurality of pixels. A drive control step for controlling the operation of the imaging device to output the imaging signal, a focus control step for performing autofocus control, and a region in which a characteristic part of the subject image is captured from an image based on the imaging signal In the first mode, the image capturing apparatus executes the detection step, and the drive control step outputs the image signal corresponding to a predetermined number of pixels among all the pixels in the image sensor. The image pickup device outputs the image pickup signal, and the focus control step is performed based on the image pickup signal output by the image pickup device in the first mode. And the detection step detects an area in which a characteristic part of the subject image is captured from an image based on the imaging signal output by the imaging element in the first mode, and performs the driving control. The step is a second mode in which the imaging signal corresponding to the image of the area detected in the detection step is output, and the imaging signal is output to the imaging element, and the focus control step further includes the imaging element. Is a program that performs autofocus control based on the imaging signal output in the second mode.

  According to the present invention, autofocus can be performed with higher accuracy.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram illustrating the configuration of the imaging apparatus according to the present embodiment. The imaging apparatus includes a photographing lens 1, an imaging element 2, a drive control unit 3, a readout setting unit 4, a lens drive control unit 5, an AF (Auto-Focus, autofocus) evaluation calculation unit 6, and an image processing unit. 7, a face detection unit 8, a display control unit 9, a display unit 10, a CPU 11, and a shutter switch 12.

  First, an outline of the imaging apparatus will be described. The taking lens 1 forms an optical image. The image sensor 2 photoelectrically converts the optical image and outputs an image signal. This imaging signal is an analog signal and is converted into a digital signal by an analog / digital conversion unit (not shown). The readout setting unit 4 sets the readout area and readout method of the imaging signal output from the imaging device 2. The drive control unit 3 controls the drive of the image sensor 2 based on the setting of the readout setting unit 4. The lens drive control unit 5 performs drive control of the photographing lens 1. The AF evaluation calculation unit 6 calculates an AF evaluation value using the digital signal converted by the analog / digital conversion unit. The image processing unit 7 performs image processing. Specifically, the image processing unit 7 performs image processing such as converting a digital signal converted by the analog / digital conversion unit into a color signal. The face detection unit 8 detects a face included in the image based on the color signal output from the image processing unit 7. The display control unit 9 performs control for displaying an image based on the color signal output from the image processing unit 7 on the display unit 10. The display unit 10 displays an image. The CPU 11 controls the entire imaging apparatus. The shutter switch 12 receives an imaging command.

  Next, details of the imaging apparatus will be described. The photographic lens 1 is driven by the lens drive controller 5 and is configured to change the in-focus state of the image formed on the image sensor 2. At the time of automatic focusing, the CPU 11 determines the driving amount of the photographing lens based on the AF evaluation value calculated by the AF evaluation calculation unit 6. The lens drive control unit 5 drives the photographing lens 1 based on the driving amount of the photographing lens determined by the CPU 11. The focus control unit includes the lens drive control unit 5, the AF evaluation calculation unit 6, and the CPU 11.

  The image sensor 2 is an element capable of performing pixel addition readout, thinning readout, and horizontal and vertical cutout readout. Pixel addition readout is a readout method in which one imaging signal is output from a plurality of pixels. For example, one imaging signal is output from four adjacent pixels. Thinning-out readout is a readout method in which pixels that output an imaging signal at a constant interval among a plurality of pixels arranged in a row are set. For example, an imaging signal is output for every three pixels, and the two pixels therebetween do not output an imaging signal. The horizontal and vertical cutout readout is a readout method for determining an area of a pixel that outputs an imaging signal among a plurality of pixels arranged in a row. For example, among a plurality of pixels, pixels included in an area defined by 1000 pixels in the horizontal direction and 500 pixels in the vertical direction output an imaging signal. Note that in the horizontal and vertical cutout readout, the amount of image pickup signal output by the image pickup device 2 is small, so that the image pickup signal can be output at high speed.

  The AF evaluation calculation unit 6 calculates an evaluation value for performing contrast-type automatic focusing control when the shutter switch 12 is half-pressed by a user operation. The face detection unit 8 detects a face included in the color signal output from the image processing unit 7. Subsequently, the face detection unit 8 detects an area (face area) including the detected face. For example, the face area is an area defined by 1000 pixels in the horizontal direction and 500 pixels in the vertical direction centering on the detected face position.

  The display control unit 9 performs processing such as converting the resolution of the color signal output from the image processing unit 7 as control for displaying an image based on the color signal output from the image processing unit 7 on the display unit 10. In addition, the display timing is adjusted. The display unit 10 is a display device such as an LCD (Liquid Crystal Display) or EVF (Electronic View Finder).

  Next, referring to FIG. 2, the relationship between the timing at which the imaging device 2 outputs the imaging signal, the timing at which the display unit 10 displays the live view image, and the timing at which the AF evaluation calculation unit 6 performs the AF evaluation value calculation. Will be explained. FIG. 2 shows the readout mode of the image sensor 2 (part 201), the timing at which the image sensor 2 outputs an imaging signal (part 202), and the timing at which the display unit 10 displays the live view image (reference numeral 203). ), The timing at which the AF evaluation calculation unit 6 calculates the AF evaluation value (part 204), images 210 and 211 (part 205) corresponding to the reading mode of the image sensor 2, and the image sensor 2 shows an application (portion 206) in which the imaging signal output is used.

  When the reading mode is “addition”, the image sensor 2 captures an image at a frame rate Nfps (Frames Per Second). That is, the image sensor 2 captures an image every (1 / N) seconds. When the readout mode is “cutout”, the image sensor 2 captures an image at a frame rate of 3 Nfps. That is, the image sensor 2 captures an image every (1 / 3N) second. This is because the image sensor 2 can capture images at high speed in horizontal and vertical cutout readout.

  Further, the AF evaluation calculation unit 6 calculates an AF evaluation value based on all the imaging signals imaged by the imaging element 2. That is, the AF evaluation calculation unit 6 calculates the AF evaluation value every (1 / N) seconds when the reading mode is “addition”, and every (1 / 3N) seconds when the reading mode is “cutout”. The AF evaluation value is calculated.

  In any reading mode, the display unit 10 displays an image at a frame rate (N / 2) fps. That is, the display unit 10 updates the image to be displayed every (2 / N) seconds.

  When the readout mode is “addition”, the image sensor 2 outputs an image signal of the entire effective pixel area (wide area) of the image sensor 2. An image 210 is an image based on this imaging signal. When the readout mode is “addition”, the image sensor 2 outputs one image signal with a plurality of pixels. When the readout mode is “cutout”, the imaging device 2 outputs an imaging signal from a pixel that outputs an imaging signal of an area including a face image. An image 211 is an image based on this imaging signal.

  In the illustrated example, the reading mode is set to “addition” from the first release detection to the face area detection. In addition, after the face area is detected, in the readout mode, “cutout” and “addition” are alternately set every (1 / N) seconds. That is, even after the first release is detected, the imaging device 2 outputs the imaging signal in the read mode “addition” every (2 / N) seconds. Thereby, the display unit 10 can display an image based on the imaging signal output in the read mode “addition” even when the image to be displayed is updated every (2 / N) seconds.

  Further, the AF evaluation calculation unit 6 calculates an AF evaluation value every (1 / 3N) second when the reading mode is “cutout”. Thereby, when the reading mode is “cutout”, it is possible to perform faster AF evaluation value calculation.

Next, the operation of the imaging apparatus 1 will be described with reference to FIG.
(Step S10) The CPU 11 determines whether or not the shutter switch 12 has accepted the first release (half-pressing of the shutter switch 12). If the CPU 11 determines that the first release has been received, the process proceeds to step S11. Otherwise, step S10 is executed again.
(Step S11) The read setting unit 4 sets the read mode to “addition”. Subsequently, the drive control unit 3 performs drive control of the image sensor 2 based on the readout mode “addition”. The image sensor 2 outputs an image signal of the entire effective pixel area of the image sensor 2. Subsequently, the analog / digital conversion unit converts the imaging signal into a digital signal. Subsequently, the image processing unit 7 creates a color signal based on the digital signal. Subsequently, the display control unit 9 performs control so that the display unit 10 can display the color signal as a live view image. The display unit 10 displays a live view image. Thereafter, the process proceeds to step S12.

(Step S12) The AF evaluation calculation unit 6 calculates an AF evaluation value based on the digital signal output from the image sensor 2 in Step S11. Thereafter, the process proceeds to step S13.
(Step S13) The CPU 11 determines whether or not the AF evaluation value calculated in step S12 is within a preset range. If the CPU 11 determines that the AF evaluation value calculated in step S12 is within a preset range, the process proceeds to step S14, otherwise the process proceeds to step S16.

(Step S14) The face detection unit 8 starts detecting a face image included in the color signal created by the image processing unit 7 in step S11. Thereafter, the process proceeds to step S15.
(Step S15) The CPU 11 determines whether or not the face detection unit 8 has detected a face image. If it is determined that it has been detected, the process proceeds to step S17. Otherwise, the process proceeds to step S16.

  (Step S16) The lens drive control unit 5 drives the photographing lens 1 based on the AF evaluation value calculated in Step S12 to adjust the focus. Then, it returns to step S11. Since the photographing lens 1 is gradually focused in step S16, the AF evaluation value approaches the optimum value by repeating steps S11 to S16. Note that the AF evaluation value used in step S16 is a value based on the imaging signal read in the readout mode “addition”, which is a mode in which one imaging signal is output from a plurality of pixels. Therefore, the focus is rough at this point.

  (Step S <b> 17) The read setting unit 4 alternately sets “cutout” and “addition” as read modes every (1 / N) seconds. The drive control unit 3 performs drive control of the image sensor 2 based on the readout modes “cutout” and “addition”. The image sensor 2 outputs an image signal corresponding to the read mode. When the reading mode is “cutout”, the cutout range is an area including the face image detected in step S15. When the readout mode is “cutout”, the imaging device 2 outputs an imaging signal every (1 / 3N) second. Subsequently, the analog / digital conversion unit converts the imaging signal into a digital signal. Subsequently, the image processing unit 7 creates a color signal based on the digital signal. Subsequently, when the reading mode is “addition”, the display control unit 9 performs control so that the display unit 10 can display a color signal as a live view image, and the display unit 10 displays a color image. Thereafter, the process proceeds to step S18.

(Step S18) The AF evaluation calculation unit 6 calculates an AF evaluation value based on the digital signal output from the analog / digital conversion unit in step S17. Thereafter, the process proceeds to step S19.
(Step S19) The CPU 11 determines whether or not the AF evaluation value calculated in step S18 is a value within a preset range. If the CPU 11 determines that the AF evaluation value calculated in step S18 is within a preset range, the process proceeds to step S21, and otherwise the process proceeds to step S20. In order to perform focusing with high accuracy, the range set in advance is smaller in step S19 than in step S13.

  (Step S20) The lens drive control unit 5 drives the photographing lens 1 based on the AF evaluation value calculated in Step S18 to adjust the focus. Then, it returns to step S17. Since the photographing lens 1 is gradually focused in step S20, the AF evaluation value approaches the optimum value by repeating steps S17 to S20. The AF evaluation value used in step S20 is based on the imaging signal output by the imaging device 2 in the readout mode “addition” and the imaging signal output by the imaging device 2 in the readout mode “cutout”. Further, in the readout mode “cutout”, the imaging device 2 outputs an imaging signal every (1 / 3N) second. Thereby, the focus can be adjusted at high speed.

  (Step S <b> 21) The CPU 11 inputs an in-focus sign image, which is a display notifying the operator that the focus has been achieved, to the display control unit 9. The display control unit 9 performs control to display the in-focus sign image on the display unit 10. The display unit 10 displays an in-focus sign image. Thereafter, the process ends. When the focus sign image is displayed on the display unit 10, the operator fully presses the shutter switch 12 (second release). The CPU 11 releases the shutter when the shutter switch 12 is fully pressed.

  Note that in step S20, the operator may be notified of the in-focus state using voice. In step S20, since the focus is on, the shutter may be automatically released. Further, when the reading mode is “cutout” in step S17, the cutout range is an area including the face detected in step S15, but may be a fixed area set by the user.

  In step S20, the lens drive control unit uses an AF evaluation value based on the imaging signal output by the imaging device 2 in the readout mode “addition” and the imaging signal output by the imaging device 2 in the readout mode “cutout”. 5 is focused, but the lens drive controller 5 may focus using only the AF evaluation value based on the imaging signal output from the imaging device 2 in the readout mode “cutout”.

  As described above, according to the present embodiment, an imaging signal that can be roughly focused using an imaging signal obtained by capturing an entire image and that can detect a characteristic portion is acquired. Subsequently, the feature portion is detected, and autofocus is performed using an imaging signal obtained by imaging the detected feature portion. As a result, the feature portion can be focused with high accuracy regardless of the portion of the entire image. That is, even when the subject moves suddenly, the focus can be followed quickly.

  In addition, since the focus is first adjusted roughly based on the imaging signal of the feature portion imaged in a state where the focus is roughly in focus, the feature portion can be focused more quickly.

  Further, since the entire image is captured at a predetermined interval, the display unit can always display the entire image on the display unit even when the characteristic portion is captured. That is, it is possible to focus at higher speed while displaying the entire image as a live view image on the display unit.

  Note that the whole or a part of the functions of the image pickup apparatus in the above-described embodiment records a program for realizing these functions on a computer-readable recording medium, and the program recorded on the recording medium is stored in a computer system. You may implement | achieve by making it read in and executing. Here, the “computer system” includes an OS and hardware such as peripheral devices.

  The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” dynamically holds a program for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system that serves as a server or a client in that case may also be included that holds a program for a certain time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

1 is a configuration diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention. In this embodiment, it is the figure which showed the timing which an image pick-up element outputs a digital signal. It is the flowchart which showed the operation | movement procedure of the imaging device in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Shooting lens, 2 ... Image sensor, 3 ... Drive control part, 4 ... Reading setting part, 5 ... Lens drive control part, 6 ... AF evaluation calculating part, 7 ..Image processing unit, 8 ... Face detection unit, 9 ... Display control unit, 10 ... Display unit, 11 ... CPU, 12 ... Shutter switch

Claims (4)

An imaging element that generates an imaging signal by photoelectrically converting a subject image formed by the imaging optical system with a plurality of pixels;
A drive control unit that controls the operation of the imaging device outputting the imaging signal;
A focus control unit for performing autofocus control;
A detection unit for detecting a region in which a characteristic part of the subject image is captured from an image based on the imaging signal;
With
The drive control unit causes the imaging element to output the imaging signal in a first mode in which the imaging signal corresponding to a predetermined number of pixels among all the pixels in the imaging element is output;
The focus control unit performs autofocus control based on the imaging signal output by the imaging element in the first mode,
The detection unit detects an area in which a characteristic portion of the subject image is captured from an image based on the imaging signal output by the imaging element in the first mode;
The drive control unit further causes the imaging element to output the imaging signal in a second mode in which the imaging signal corresponding to the image of the region detected by the detection unit is output,
The focus control unit further performs autofocus control based on the imaging signal output by the imaging element in the second mode. The imaging apparatus according to claim 1, wherein when the subject image is a human image, the detection unit determines an area in which a face portion of the subject image is captured. 3. The image pickup device according to claim 1, wherein the image pickup device outputs the image pickup signal at a high frame rate in the second mode as compared with the first mode. 4. Imaging device. A program for controlling the operation of an imaging apparatus including an imaging element that generates an imaging signal by photoelectrically converting a subject image formed by an imaging optical system with a plurality of pixels,
A drive control step for controlling an operation in which the imaging element outputs the imaging signal;
A focus control step for performing autofocus control;
A detection step of detecting a region in which a characteristic part of the subject image is captured from an image based on the imaging signal;
To the imaging device,
In the first mode in which the drive control step outputs the imaging signal corresponding to a predetermined number of pixels among all the pixels in the imaging element, the imaging element is caused to output the imaging signal,
The focus control step performs autofocus control based on the imaging signal output by the imaging device in the first mode,
The detecting step detects an area in which a characteristic part of the subject image is captured from an image based on the imaging signal output by the imaging element in the first mode;
The drive control step further causes the imaging element to output the imaging signal in a second mode in which the imaging signal corresponding to the image of the region detected in the detection step is output,
The focus control step further performs autofocus control based on the imaging signal output by the imaging device in the second mode.

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