JP2009044535A - Electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify process for making the sharpness of an image obtained by an image sensor different in the image. <P>SOLUTION: An electronic camera is equipped with a focus detecting means 3 which divides the luminous flux of an object which has passed through photo-optical system 1 into two systems to detect defocus information based on the phase difference between two images formed respectively of the optical flux of 2 systems, the image sensor 3 with the optical systems which divides the luminous flux of object into two systems and which is formed on substantially the whole region of an imaging surface and an image processing means 4 for making the sharpness of the image obtained by the image sensor 3 different based on the distribution of the defocus information in the imaging surface detected by the focus detecting means 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic camera.

  A technique for measuring a distance to a subject and performing different filter processing on an imaging space grouped according to the distance is disclosed (see Patent Document 1).

JP 2006-67521 A

  In the prior art, the distance to the subject is measured using infrared rays or the like. For this reason, it is necessary to measure the distance to each subject while emitting infrared light toward all subjects within the shooting angle of view, in addition to being exactly the same as the distance to the imaging surface of the image sensor.

(1) An electronic camera according to the present invention divides a subject light beam that has passed through a photographing optical system into two systems, and detects focus information based on a phase difference between two images formed by the two light beams. Acquired by the image pickup device based on the distribution of the defocus information on the image pickup surface detected by the focus detection means and the image pickup device in which the optical system that divides the subject light flux into two systems is formed over substantially the entire image pickup surface And image processing means for varying the sharpness of the image to be processed.
(2) In the electronic camera according to claim 1, the image processing means includes at least one of a process of changing the spatial frequency of the image, a process of changing the strength of image outline enhancement, and a process of changing the gain at the time of γ correction. It is preferable to carry out.
(3) In the electronic camera according to claim 2, the image processing means classifies the images acquired by the image sensor into a plurality of groups according to the size of the defocus information, and between the classified image regions. It is preferable to vary at least one of the spatial frequency, the strength of edge enhancement, and the gain at the time of γ correction.
(4) In the electronic camera according to claim 3, the image processing means can lower the spatial frequency, weaken the edge enhancement, and lower the gain at the time of γ correction in the region corresponding to the distant view in the image.

  The electronic camera according to the present invention simplifies the process of making the sharpness of the image acquired by the image sensor different in the image.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining a main configuration of an electronic camera according to an embodiment of the present invention. The electronic camera is controlled by the control device 4.

  The taking lens 1 forms a subject image on an image pickup surface of an image pickup element to be described later. The distance measuring device and imaging device 3 includes an imaging device, an AFE (Analog Front End) circuit, an A / D conversion circuit, and a defocus amount calculation circuit.

  The image sensor is constituted by, for example, a CMOS image sensor 31 (FIG. 2). The image sensor 31 captures a subject image and outputs an analog image signal to the AFE circuit. The AFE circuit performs analog processing on the analog image signal (such as signal amplification in accordance with the instructed ISO sensitivity). The ISO sensitivity changes the imaging sensitivity (exposure sensitivity) within a predetermined range (for example, equivalent to ISO 50 to ISO 1000) in accordance with a sensitivity setting instruction from the control device 4. The imaging sensitivity is a controlled amount that changes the amplification factor of signal amplification performed by the AFE circuit. The imaging sensitivity value is represented by a corresponding ISO sensitivity value. The A / D conversion circuit converts the image signal after analog processing into a digital signal. The digital image signal is output to the image processing unit 4a in the control device 4.

  The image processing unit 4a performs image processing on the input digital image signal. Image processing includes, for example, γ conversion processing, contour enhancement processing, filter processing, color temperature adjustment (white balance adjustment) processing, format conversion processing for image signals, image compression / decompression processing, and the like. The buffer memory 4b temporarily stores data before and after image processing and during image processing, stores an image file before recording on the recording medium 9, and stores an image file read from the recording medium 9. Used for.

  The display circuit 6 creates display data for displaying a captured image on the liquid crystal monitor 7 and displaying an operation menu on the liquid crystal monitor 7. The liquid crystal monitor 7 displays a reproduced image or menu screen based on the created display data.

  The control device 4 inputs a signal output from each block, performs a predetermined calculation, and outputs a control signal based on the calculation result to each block. The operation member 8 includes operation switches for an electronic camera. The operation member 8 outputs an operation signal from each operation switch to the control device 4 such as a half-press switch, a full-press switch, a menu operation key, and the like that are turned on / off in conjunction with a pressing operation of a release button (not shown). .

  The recording medium 9 includes a memory card that can be attached to and detached from the electronic camera. In the recording medium 9, image data and an image file including the information are recorded according to an instruction from the control device 4. The image file recorded on the recording medium 9 can be read by an instruction from the control device 4.

<Focus detection processing>
The electronic camera according to the present embodiment detects a focus adjustment state by the photographing lens 1 using a light beam incident on a focus detection region on the image sensor 31 by a so-called phase difference detection method. FIG. 2 is a diagram for explaining a pixel row for focus detection formed in the image sensor 31. Among the pixels of the image sensor 31, the pixel column A, the pixel column B, the pixel column C,... Provided for each predetermined pixel column in the horizontal direction are different from normal pixel columns and are each configured with focus detection pixels. The Each focus detection pixel is subjected to masking for pupil division.

  Specifically, substantially half of the on-chip microlens formed corresponding to the pixel is shielded from light. FIG. 3 is an enlarged view of the minute region 310 of the focus detection pixel column of FIG. In each pixel, the left half or right half is masked alternately. Thereby, between the pixels adjacent in the horizontal direction, the half faces masked or the half faces not masked are adjacent to each other.

  FIG. 4 is a diagram illustrating a focus detection pixel column and a light beam incident on the pixel column. In FIG. 4, a light beam (referred to as an A component) from the left direction enters a photodiode of a pixel whose right half surface is masked. A light beam (referred to as a B component) from the right direction is incident on the photodiode of the pixel whose left half surface is masked.

  As a result, the pixel output (photoelectric conversion signal value) obtained from the pixel group to which the A component light beam is incident represents an image by the light beam incident from one half of the exit pupil of the photographing lens 1, and the B component light beam is A pixel output (photoelectric conversion signal value) obtained from the incident pixel group represents an image of a light beam incident from the other half of the exit pupil.

  FIG. 5 is a diagram illustrating a pixel output waveform obtained when focusing on the main subject. In FIG. 5, the horizontal axis represents the pixel position, and the vertical axis represents the pixel output. Since a sharp image is formed on the image sensor 31 at the time of focusing, a pair of images formed by pupil-divided light beams coincide on the image sensor 31. That is, the A component waveform and the B component waveform obtained from the pixel group constituting the focus detection pixel column overlap in shape.

  FIG. 6 is a diagram illustrating a pixel output waveform obtained when the main subject is out of focus. In FIG. 6, the horizontal axis represents the pixel position, and the vertical axis represents the pixel output. At the time of out-of-focus, a state where a sharp image is formed in front of the image sensor 31 or a state where a sharp image is formed on the back side of the image sensor 31, the pair of images formed by the pupil-divided light beams coincide on the image sensor 31. do not do. In this case, the A component waveform and the B component waveform have different positional relationships (shift direction and shift amount Δd) between the A component waveform and the B component waveform in accordance with the shift (defocus amount) from the focused state.

  A defocus amount calculation circuit in the distance measuring device / imaging device 3 calculates a focus position adjustment state (defocus amount) by the photographing lens 1 based on a positional relationship between the A component waveform and the B component waveform, and calculates the calculation result. It is sent to the control device 4. When the control device 4 outputs a lens drive signal (a signal for instructing the lens drive direction and the lens drive amount) according to the defocus amount to the lens drive mechanism 5, the lens drive mechanism 5 moves the focus lens 2 forward and backward in the optical axis direction. Let Thereby, focus adjustment is performed.

  Note that the comparison region illustrated in FIGS. 5 and 6 is a region that commonly includes feature points (for example, local maximum values) extracted from the A component waveform and the B component waveform. The defocus amount calculation circuit obtains the defocus amount using the waveform data in the comparison region among the A component waveform and the B component waveform obtained from the pixel group constituting the focus detection pixel column.

<Measurement of phase difference distribution>
In the electronic camera according to the present embodiment, since the image sensor 31 has focus detection pixel rows in almost the entire area of the imaging surface, the positional relationship between the A component waveform and the B component waveform, that is, phase difference information is obtained in almost the entire area of the imaging screen. You can get it. The phase difference information corresponds to the distance to the subject corresponding to the subject image formed on the pixel group that outputs the A component waveform and the B component waveform (shooting distance from the electronic camera to the subject). Therefore, if the phase difference information is obtained for each predetermined area on the image sensor 31, the photographing distance information to all the subjects existing in the photographing screen can be obtained.

  FIG. 7A is a diagram illustrating a state in which the photographing lens 1 forms a sharp image of the subject 71 on the imaging surface of the image sensor 31 (focused on the subject 71). FIG. 7B is a diagram illustrating a pixel output waveform obtained with respect to the image of the subject 71 from the focus detection pixel array. In FIG. 7B, the horizontal axis represents the pixel position, and the vertical axis represents the pixel output. In the in-focus state, the phase difference between the A component waveform and the B component waveform is substantially zero.

  FIG. 8A is a diagram illustrating a case where the photographing lens 1 forms an image of the subject 72 on the imaging surface of the image sensor 31 in the focus adjustment state illustrated in FIG. FIG. 8B is a diagram illustrating a pixel output waveform obtained with respect to the image of the subject 72 from the focus detection pixel array. In FIG. 8B, the horizontal axis represents the pixel position, and the vertical axis represents the pixel output. Since the subject 72 is farther from the electronic camera than the subject 71, a phase difference occurs between the A component waveform and the B component waveform when the subject 72 is in focus (the subject 72 is out of focus). In the case of the optical system exemplified in this embodiment, a phase difference in which the A component waveform is shifted to the right by Δd with respect to the B component waveform is detected.

  FIG. 9 is a diagram illustrating a distribution of phase differences detected for each predetermined area on the shooting screen. “0” represents an in-focus (focus plane) area. A positive number represents a subject area far from the focal plane. A negative number represents a subject area closer to the focus plane. “-” Represents an area in which the phase difference cannot be detected because the feature points of the A component waveform and the B component waveform cannot be detected. Here, the image 71 a represents the image of the subject 71, and the image 72 a represents the image of the subject 72.

  The control device 4 performs an interpolation process using the phase difference distribution illustrated in FIG. 9, and a region in which no phase difference is detected (that is, a region corresponding to a pixel column in which no focus detection pixel column is provided, and 9, the phase difference information for the region indicated by “−” is calculated. FIG. 10 is a diagram illustrating the phase difference distribution after the interpolation processing. The point that the image 71a represents the image of the subject 71 and the image 72a represents the image of the subject 72 is the same as in the case of FIG.

<Image blur processing>
The control device 4 performs different image processing (for example, γ conversion processing, contour emphasis processing, and filter processing) between areas of the shooting screen in accordance with the above-described phase difference distribution, thereby blurring the edges of the image. Reduce contrast by reducing contrast. For this purpose, the control device 4 groups the photographing screens into a predetermined number (for example, 3) of regions based on the phase difference distribution (FIG. 10) after the interpolation processing. FIG. 11 is a diagram illustrating a grouped area. According to the example of FIG. 11, the first region 111 having phase difference information less than 5; the second region 112 having phase difference information of 5 or more and less than 15; and the third region 113 having phase difference information of 15 or more. Divided into three. The first area 111 corresponds to the subject image 71 a, the second area 112 corresponds to the subject image 72 a, and the third area 113 corresponds to the background image farther from the subjects 71 and 72.

The control device 4 adds image blur by making the sharpness of the image in the first region 111 the highest and making the image sharpness in the third region 113 the lowest. For this purpose, the control device 4 performs at least one of the following processes.
[A] A band pass filter (BPF) process for increasing the low frequency components of the spatial frequency in the third region 113 and reducing the high frequency components in the order of the first region-second region-third region is performed.
[B] The gain of the γ conversion processing in the third region 113 is weakened in the order of the first region-second region-third region.
[C] The gain of the contour enhancement processing in the third region 113 is weakened in the order of the first region-second region-third region. FIG. 12 is a diagram exemplifying processing contents for each area and each process.

Camera processing performed by the electronic camera described above will be described with reference to the flowcharts of FIGS.
<Release standby processing>
FIG. 13 is a flowchart illustrating the flow of a release standby process executed by the control device 4. In step S10, the control device 4 determines whether or not a release operation has been accepted. When an operation signal indicating that the release button has been fully pressed is input from the operation member 8, the control device 4 makes a positive determination in step S10 and proceeds to step S20. When the operation signal indicating that the release button has been fully pressed is not input from the operation member 8, the control device 4 makes a negative determination in step S10 and performs a release standby while repeating the determination process.

  In step S20, the control device 4 performs a release process and returns to step S10. Details of the release process will be described later.

<Release processing>
In step S21 of FIG. 14, the control device 4 performs an AF (autofocus) process and proceeds to step S22. Details of the AF processing will be described later. In step S <b> 22, the control device 4 performs a shooting process and ends the process of FIG. 14. Details of the photographing process will be described later.

<AF processing>
In step S211 of FIG. 15, the control device 4 determines an AF execution area and proceeds to step S212. For example, the control device 4 sets the focus detection area designated by the operation signal from the operation member 8 as the AF execution area.

  In step S212, the control device 4 sends an instruction to the distance measuring device / imaging device 3 to read out the signal from the phase difference detection pixel row of the image sensor 31 corresponding to the AF execution area, and then proceeds to step S213.

  In step S213, the control device 4 sends an instruction to the distance measuring device / imaging device 3, measures the phase difference (calculates the defocus amount), and proceeds to step S214. In step S214, the control device 4 calculates a focus lens driving amount necessary for focusing from the phase difference, and proceeds to step S215. In step S215, the control device 4 sends an instruction to the lens driving mechanism 5, drives the focus lens 2, and proceeds to step S216.

  In step S216, the control device 4 determines whether or not the focus lens 2 has reached the target position. When the control device 4 receives a signal indicating that the lens driving is completed from the lens driving mechanism 5, the control device 4 makes an affirmative determination in step S216, ends the processing in FIG. 15, and proceeds to step S22 in FIG. When the control device 4 does not receive a signal indicating that the lens driving is completed from the lens driving mechanism 5, the control device 4 makes a negative determination in step S216 and waits for the lens driving to be completed while repeating the determination processing.

<Shooting process>
In step S221 in FIG. 16, the control device 4 sends an instruction to the distance measuring device / imaging device 3 to acquire image data, and the process proceeds to step S222. As a result, the distance measuring device / imaging device 3 captures a subject image and reads out signals from all the pixels of the image sensor 31.

  In step S222, the control device 4 sends an instruction to the distance measuring device / imaging device 3 to extract a signal from a corresponding phase difference detection (focus detection) pixel row for each of the predetermined regions illustrated in FIG. Proceed to step S223. In step S223, the control device 4 sends an instruction to the distance measuring device / imaging device 3, calculates the phase difference distribution for each region, and proceeds to step S224. By performing the interpolation process, the phase difference distribution illustrated in FIG. 10 is obtained.

  In step S224, the control device 4 sends an instruction to the distance measuring device / imaging device 3, groups the shooting screens according to the phase difference distribution, and proceeds to step S225. In step S225, the control device 4 causes the image processing unit 4a to perform different image processing (γ conversion processing, contour emphasis processing, filter processing) on the captured image acquired in step S221 in the grouped regions. The process proceeds to S226.

  In step S226, the control device 4 saves the file including the image data after the image processing in the recording medium 9, and ends the processing in FIG.

According to the embodiment described above, the following operational effects can be obtained.
(1) Since the electronic camera includes the image sensor 31 including a pixel array for phase difference detection used for phase difference detection AF, a pair of pupil-divided images can be acquired on an imaging surface for acquiring a captured image. . Thereby, as in the case where the focus sensor used for phase difference detection AF is provided separately from the image sensor, the occurrence of out-of-focus due to the fact that the imaging surface of the image sensor and the imaging surface of the focus sensor do not exactly match is prevented. be able to.

(2) Since the pixel row for phase difference detection is provided at a predetermined pixel interval substantially over the entire imaging surface of the image sensor 31, photographing distance information (phase difference information) to the subject can be obtained over substantially the entire photographing screen. Unlike the prior art, it is not necessary to individually measure the distances to all subjects within the shooting angle of view, so the time required for distance measurement and the burden of measurement processing can be reduced.

(3) Since image processing (γ conversion processing, contour enhancement processing, and filter processing) to be performed on the captured image is varied according to the distribution of the phase difference information, different processing is performed for a subject with a short photographing distance and a subject with a long photographing distance. It can be performed. For example, a camera with a short actual focal length, such as an electronic camera having a small imaging area of an image sensor compared to a 35 mm version camera, often has a flat captured image and a poor sense of depth. In such a case, if an image blur is added to a distant subject, the image can have a sense of depth.

(4) The photographing screens are grouped according to the distribution of the phase difference information, and the image processing is varied for each grouped region. When the number of groups is three, it is only necessary to perform three types of image processing, so that the burden of image processing can be reduced as compared with the case where three or more types of image processing are performed.

(Modification 1)
The image sensor 31 described above has been described so as to provide a pixel row for phase difference detection for each predetermined pixel row. However, all the pixel rows in the horizontal direction (that is, all pixels of the image sensor 31) are pixels for phase difference detection. It may be configured.

(Modification 2)
Image processing for adding image blur, that is, processing for blurring image edges and reducing image contrast to reduce image sharpness includes at least one of the above-described γ conversion processing, contour enhancement processing, and filtering processing. One process may be performed, or each process may be performed in combination.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

It is a block diagram explaining the principal part structure of the electronic camera by one embodiment of this invention. It is a figure explaining the pixel row | line for focus detection formed in an image sensor. It is an enlarged view of a pixel row for focus detection. It is a figure explaining the focus detection pixel row | line and the light beam which injects into a pixel row | line. It is a figure which illustrates the pixel output waveform obtained at the time of focusing. It is a figure which illustrates the pixel output waveform obtained at the time of non-focusing. (a) is a figure which illustrates the state which ties a sharp image on the imaging surface of an image sensor. (b) is a diagram illustrating a pixel output waveform. (a) is a figure which illustrates the case where the image of another subject is formed on the imaging surface of the image sensor. (b) is a diagram illustrating a pixel output waveform. It is a figure which illustrates phase difference distribution detected for every predetermined field of a photography screen. It is a figure which illustrates phase difference distribution after interpolation processing. It is a figure which illustrates the field divided into groups. It is a figure which illustrates the processing content for every process for every area | region divided into groups. It is a flowchart explaining the flow of a release standby process. It is a flowchart explaining the flow of a release process. It is a flowchart explaining the flow of AF process. It is a flowchart explaining the flow of imaging | photography process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Shooting lens 2 ... Focus lens 3 ... Distance measuring device and imaging device 4 ... Control apparatus 4a ... Image processing part 4b ... Buffer memory 5 ... Lens drive mechanism 6 ... Display circuit 7 ... Liquid crystal monitor 8 ... Operation member

Claims (4)

A focus detection unit that divides a subject luminous flux that has passed through the photographing optical system into two systems, and detects defocus information based on a phase difference between two images formed by the two luminous fluxes;
An imaging device in which an optical system for dividing the subject luminous flux into two systems is formed over substantially the entire area of the imaging surface;
An electronic camera comprising: an image processing unit that varies a sharpness of an image acquired by the imaging device based on a distribution of defocus information on the imaging surface detected by the focus detection unit. The electronic camera according to claim 1,
The electronic camera is characterized in that the image processing means performs at least one of a process of changing a spatial frequency of an image, a process of changing the intensity of image edge enhancement, and a process of changing a gain at the time of γ correction. The electronic camera according to claim 2,
The image processing means classifies the images acquired by the image sensor into a plurality of groups according to the size of the defocus information, and performs spatial frequency and contour enhancement between the classified areas of the images. An electronic camera characterized in that at least one of strength and gain at the time of γ correction is made different. The electronic camera according to claim 3.
The electronic camera according to claim 1, wherein the image processing means lowers the spatial frequency, weakens the edge enhancement, and lowers the gain during the γ correction in a region corresponding to a distant view in the image.

Images