JP2007047415A - Imaging apparatus and focus adjusting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve focusing accuracy by restraining the deviation of a focusing position resulting from the chromatic aberration of an image forming optical system. <P>SOLUTION: The imaging apparatus has: a focusing position detection means for detecting the focusing position of a focus lens for focus adjustment corresponding to an optional position in a photographic image plane or a range-finding area set out of a plurality of predetermined positions; a storage means for storing the color information of a subject and focusing position correction amount in accordance with the position on the photographic image plane in the range-finding area; and a control means for controlling to correct the focusing position of the focus lens by using the focusing position correction amount stored in the storage means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus using an image pickup element, and more particularly to an automatic focusing (AF) technique thereof. The invention also relates to a focus adjustment device.

  Conventionally, in an imaging apparatus using an imaging element such as a CCD sensor or a CMOS sensor, such as a digital camera or a video camera, an automatic focus detection apparatus that performs a focusing operation using a high-frequency component of a luminance signal obtained from the imaging element has been used. It has been. In this automatic focus detection apparatus, while moving the focus lens, the high frequency component of the luminance signal in the distance measurement area set in the screen is integrated to detect the lens position with the highest contrast as the focal point.

  However, this focus detection method (integration type) has a problem that the focus position may be shifted due to the color and temperature of the subject and the characteristics of the imaging optical system, particularly chromatic aberration. To solve this, color information is extracted from the ranging area in the captured image, and the focus position is shifted based on the detected color information, thereby correcting the shift of the focus detection position caused by the chromatic aberration of the imaging optical system. An automatic focusing device has also been proposed (for example, Patent Document 1).

JP 2004-347665 A

  The chromatic aberration of the imaging optical system not only changes depending on the color of the subject, but also changes depending on the subject distance. Therefore, when the same correction amount is applied at any subject distance, the correction error increases depending on the subject distance, and as a result, the focusing accuracy may decrease.

  In addition, in an imaging apparatus having such an imaging optical system, the distance measurement area for detecting the subject distance is not one place and a fixed position, but one of a plurality of predetermined positions on the imaging screen, or the imaging screen Some focus adjustments can be made at any specified position. In such an imaging device (an imaging device capable of multipoint ranging), there is a problem in that the correction amount varies depending on the position of the ranging area due to differences in curvature of field and chromatic aberration due to the image height of the imaging optical system. is there.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an imaging apparatus and a focus adjustment apparatus that achieves further improvement in focusing accuracy.

  The gist of the present invention is that the focus of the present invention is to detect the in-focus position of the focus adjustment focus lens corresponding to the range-finding area set from an arbitrary position or a predetermined plurality of positions in the shooting screen. Using the position detection means, storage means for storing the focus position correction amount according to the position of the subject color information and the position measurement area on the shooting screen, and the focus position correction amount stored in the storage means, It is achieved by an imaging device comprising control means for controlling to correct the in-focus position of the focus lens.

  Further, the above-described object is to provide a focus position detection unit that detects a focus position of a focus lens for focus adjustment corresponding to a distance measurement area set from an arbitrary position or a predetermined plurality of positions on a shooting screen. Control means for controlling to correct the focus position of the focus lens using the focus position correction amount according to the color information of the subject and the position of the distance measurement area on the shooting screen. This is also achieved by the focusing device.

  With such a configuration, the focusing accuracy can be improved according to the present invention.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration example of an imaging apparatus according to an embodiment of the present invention.
In the imaging device 100 of the present embodiment, the imaging lens 101 forms an imaging optical system of the imaging device 100. The imaging lens 101 includes a focus lens 102 that moves back and forth in accordance with the control of the focus lens driving unit 115 and performs focus adjustment. The imaging element 103 is, for example, a CCD sensor or a CMOS sensor, and converts the light incident from the imaging lens 101 into an electrical signal and outputs it.

  The A / D converter 104 digitizes an analog signal from the image sensor 103 and outputs it as digital image data. The temporary storage unit 106 is a memory that temporarily stores digital image data. The image processing unit 107 applies image processing (also referred to as development processing) such as pixel interpolation and white balance processing to the image data output from the A / D converter 104.

  For example, a display image having a smaller number of pixels than the number of pixels of the image sensor 103 is continuously generated by the image processing unit 107 and displayed on the display device 105 such as an LCD, thereby making the display device 105 an electronic viewfinder (EVF). ).

  The recording unit 108 records the image data for recording output from the image processing unit 107 on a recording medium represented by a semiconductor memory card or a magnetic tape, for example, when shooting is instructed by pressing the shutter button fully. Write. The imaging lens state detection unit 109 detects the zoom position and aperture value of the imaging lens 101.

  The output signal of the A / D converter 104 is input to the ranging area signal extracting unit 116 in addition to the temporary storage unit 106. The ranging area signal extraction unit 116 extracts a ranging area signal from the A / D converter 104 and supplies the signal to the color information detection unit 110 and the extraction unit 111. The position of the distance measurement area in the imaging screen is automatically set by the system control unit 118 to be described later from information on the subject in the image stored in the temporary storage unit 106 or set in advance by the photographer. And

  The color information detection unit 110 detects color information of a predetermined distance measurement area from the digital image data, and outputs the detection result to a position correction amount calculation unit 114 described later. The extraction unit 111 extracts a signal indicating a high frequency component by applying, for example, orthogonal transformation to the pixels included in the distance measurement region of the digital image data, and outputs the signal to the in-focus position detection unit 112.

  The focus position detection unit 112 performs the above-described integral focus position detection based on the signal extracted by the extraction unit 111. In the present embodiment, the focus position correction amount includes the zoom position of the photographing lens 101 (when the photographing lens is a zoom lens), the aperture value, the subject distance (focal position), the distance measurement area position and the distance measurement area in the photographed image. It is determined from the color information. Among these conditions, a focal position correction amount calculation table based on color information for a plurality of combinations of the zoom position and aperture value of the image pickup optical system (shooting lens 101), the distance measurement area position on the image pickup screen, and the subject distance in advance. Can be stored in the correction amount storage unit 113.

  The position correction amount calculation unit 114 uses the zoom position and aperture value information from the imaging lens state detection unit 109, the zoom position and the aperture value are equal in the correction table stored in the correction amount storage unit 113, and the subject distance. Are read out. Then, an in-focus position correction amount (a plurality of in-focus position correction amounts corresponding to discrete color evaluation values) corresponding to the designated ranging area position is obtained from each table. Next, a plurality of correction amounts corresponding to these discrete subject distances are interpolated to obtain in-focus position correction amounts corresponding to the in-focus position information (ie, subject distance information) from the in-focus position detector 112 (discrete). For each target color evaluation value).

  Then, the final focus position correction amount corresponding to the color information is calculated from the calculated focus position correction amount and the color information (color evaluation value) from the color information detection unit 110. Based on the focus position correction amount output from the position correction amount calculation unit 114, the focus lens drive control unit 115 corrects the position of the focus lens 102 and optimizes the focus position with respect to the subject.

  The system control unit 118 controls the overall operation of the imaging apparatus 100. The system control unit 118 is, for example, a CPU, and controls the operation of the imaging apparatus including the focusing operation by executing a control program stored in a program memory (not shown) and controlling each component in the imaging apparatus. To do.

  The operation unit 119 is an input device such as a button, a key, a touch panel, and a joystick, and is used for a user to give an instruction to the imaging device. The operation unit 119 includes a release 120. When the release 120 is in a half-pressed state, a distance measurement / focusing operation is performed. Further, when the release 120 is fully pressed, the actual photographing / recording operation is performed.

<Overall Operation of Imaging Device>
Hereinafter, the overall flow of processing at the time of shooting in the imaging apparatus of the present embodiment will be described using the flowchart shown in FIG. It should be noted that, unless otherwise specified in the following description, the subject of the operation is the system control unit 118.

  First, in step S301, the system control unit 118 detects the state of a main switch (power switch) (not shown) included in the operation unit 119. If it is on, the process proceeds to step S302. In step S302, the system control unit 118 checks the remaining capacity of a recording medium (not shown) mounted on the recording unit 108, and if the remaining capacity is larger than the captured image data size determined from, for example, image quality setting, the process proceeds to step S305. If not, the process proceeds to step S303.

  In step S303, the system control unit 118 warns that the remaining capacity of the recording medium is insufficient, and returns to step S301. The warning can be performed by displaying a message on the display device 105, outputting a sound from a sound output unit (not shown), or both.

  In step S305, the system control unit 118 displays the distance measurement area on the display device 105 functioning as an electronic viewfinder. This display is performed in an electronic viewfinder display process in which a captured image is stored in the temporary storage unit 106, and a display image is generated by the image processing unit 107 and displayed on the display device 105 continuously. Specifically, the system control unit 118 displays a mark or the like representing a distance measurement area that is automatically set from subject information or preset by the photographer, together with an image of the electronic viewfinder. FIG. 12 shows an example in which the distance measurement area 501 set near the center in the shooting screen 500 is displayed as an area surrounded by a dotted line.

  In step S306, the system control unit 118 checks the state of the release 120. If it is half-pressed, the system control unit 118 proceeds to step S308, otherwise proceeds to step S307. Here, the imaging apparatus according to the present embodiment starts processing prior to the main shooting, such as an automatic focusing operation (AF) and an automatic exposure control operation (AE), by pressing the release halfway. In step S307, the state of the main switch is checked. If it is on, the process returns to step S305; otherwise, the process returns to step S301.

  In step S308, the system control unit 118 detects subject luminance from the output of the A / D converter 104. In step S309, the color information detection unit 110 calculates a color evaluation value in the distance measurement area 501. A specific method for calculating the color evaluation value will be described later.

  Thereafter, an automatic focusing process (AF process) is performed in step S310. If the subject brightness is lower than the predetermined value from the detection result in step S308, AF processing is performed by projecting AF auxiliary light toward the subject for a predetermined time with a light source (not shown). Details of the AF processing will be described later.

  After focusing, in step S311, it is checked whether the release 120 is fully pressed. If it is fully pressed, the process proceeds to step S313. Otherwise, the process proceeds to step S312. Here, in the imaging apparatus of the present embodiment, the shooting process is started by fully pressing the release 120.

  In step S312, it is checked whether the release 120 is half-pressed. If half-pressed, the process returns to step S311; otherwise, the process returns to step S305. In step S313, photographing processing is performed according to the flowchart of FIG. In step S314, the remaining capacity of the recording medium is checked in the same manner as in step S302. If there is a remaining capacity necessary for the next shooting, the process proceeds to step S315. Otherwise, the process proceeds to step S303. In step S315, it is checked whether or not the release 120 is fully pressed. If not, the process proceeds to step S312.

<Outline of focus position correction>
Before describing specific AF processing, the principle and outline of focus position correction in this embodiment will be described.
FIG. 3 shows an example of the color arrangement of the color filter used by the image sensor 103 according to this embodiment. Thus, the signal (luminance signal) obtained from each pixel of the image sensor is a signal having spectral characteristics of any one of R (red), G1 (green), G2 (green), and B (blue). A luminance signal representing information of a high-definition portion of an image captured by such an image sensor is a matrix with respect to a signal obtained by sequentially reading all the pixels with respect to a signal obtained by reading only the G1 and G2 pixels in FIG. The color difference signal (correction signal) obtained by processing is composed of a sum of signals obtained by adding a certain ratio. As a result, the spectral sensitivity of the luminance signal becomes close to the visual characteristics of the human eye, which has a high sensitivity to green, as shown in FIG. 4, and it is possible to obtain an image similar to the image visually seen by the human. . Such correction is performed by the image processing unit 107, and is performed even when the color arrangement of the color filter is different from the example of FIG.

  On the other hand, the signal from which the extraction unit 111 extracts high-frequency components is simply a signal obtained by digitally converting the luminance signal obtained by sequentially reading all the pixels of the image sensor 103 into the A / D converter 104. This is synonymous with the case where white light luminance is obtained from all pixels regardless of the color of the filter.

  Therefore, the spectral sensitivity characteristic of the signal used by the in-focus position detection unit 112 for in-focus position detection is larger than the luminance signal of the recording image generated mainly using the green light at the approximate center of the visible area. The sensitivity on the short wavelength side and the long wavelength side is relatively high.

  As described above, chromatic aberration is present in the imaging optical system depending on the color within the distance measurement area of the subject. Therefore, the in-focus position determined without considering the pixel color (handled as white light luminance) is not necessarily the optimum in-focus position for a recording image mainly composed of green light luminance. Therefore, in the present embodiment, the focus position of the focus lens determined based on the white light luminance is corrected by an amount determined according to the difference in the optical characteristics of the imaging optical system with respect to the green light luminance and the white light luminance. Yes. This correction amount can be obtained based on so-called chromatic aberration, in which the focus position of the imaging optical system varies depending on the wavelength of light from the subject. This embodiment also takes into account other aberrations such as field curvature of the imaging optical system in accordance with the position of one distance measurement area selected from a plurality of distance measurement areas by automatic setting or user setting. It is.

<Determination of position correction amount>
Next, an in-focus position correction amount determination operation in the imaging apparatus according to the present embodiment will be described.
As described above, in the present embodiment, the focus position correction amount includes the zoom position of the photographing lens 101 (when the photographing lens is a zoom lens), the aperture value, the subject distance (focal position), the position of the distance measurement area, It is determined from the color information in the distance area. Of these conditions, for each of a plurality of combinations of zoom position, aperture value, and subject distance, focusing corresponding to a plurality of combinations of color evaluation values Cx, Cy and ranging area positions (image height: mm). A correction table in which position correction amounts are associated is stored in the correction amount storage unit 113.
Note that the in-focus position correction amount for a plurality of combinations of the depth of field and the color information in the captured image may be stored in the correction amount storage unit 113.

  Note that since the subject distance has more values than the zoom position and aperture value, it is not a good idea to store the correction table for all the values that the subject distance can take. Therefore, in this embodiment, as shown in FIG. 13, correction tables corresponding to discrete subject distances (tables 1 to 35 in the example of FIG. 7) are stored.

FIGS. 5A and 5B are diagrams showing examples of specific correction tables. Here, a two-dimensional graph is schematically shown so that the relationship between the value stored in the correction table and the interpolation processing using this value can be easily understood.
FIGS. 5A and 5B show two extracted tables out of a plurality of tables prepared for combinations of predetermined zoom positions and aperture values, for example, the table 6 in FIG. And correspond to Table 3.

  In this case, the correction table shown in FIG. 5A corresponds to a zoom position of 28 mm, a diaphragm 2.8, and an infinite subject distance. Then, the in-focus position correction amount corresponding to each combination of the three discrete image heights d1, d2, and d3 and the three color evaluation values (CxCy1, CxCy2, CxCy3) is stored. That is, nine coordinates indicated by ● in FIG. 5A are stored. Similarly, FIG. 5B shows a correction table corresponding to a zoom position of 28 mm, a diaphragm 2.8, and a subject distance of 1 m, and corresponds to the same combination of image height and color evaluation value as the table shown in FIG. The in-focus position correction amount to be stored is stored.

Thus, in the present embodiment, a table having nine data for each combination of zoom position, aperture value, and subject distance is stored in advance. Further, as shown in FIG. 6, the coordinates of the color evaluation values CxCy1 to CxCy3 in which the focus position correction amount is recorded are also stored in advance. Further, the image height is stored in advance for each of the plurality of distance measuring areas.
Assuming that such a preparation has been made in advance, the operation of determining the focus position correction amount will be described below.

  First, the image height corresponding to the distance measurement position determined by automatic setting or user setting by the system control unit 118 is acquired. Then, using a plurality of correction tables corresponding to the current zoom position and aperture value, for each table (that is, for each discrete subject distance), the focus position correction amount and the plurality of color evaluation values for the acquired image height An in-focus position correction amount corresponding to the combination with CxCy1 to CxCy3 is obtained. At this time, an in-focus position correction amount (indicated by x and ▲ in FIG. 5) corresponding to the image height of the distance measurement area at the time of imaging is obtained by interpolation processing using values corresponding to discrete combinations stored in advance. Coordinates) is calculated by the position correction amount calculation unit 114. As a result, focus correction amounts for combinations of three color evaluation values are obtained for each of a plurality of discrete subject distances.

  Next, the distance of the subject is calculated based on the detection information of the focus position detection unit 112. Then, the focus position correction amount calculation unit 114 obtains focus correction amounts (a, b, c) corresponding to the three color evaluation values for the calculated subject distance. As shown in FIG. 6, the calculation of the focus correction amount can be realized by linear interpolation using the focus position correction amount corresponding to the discrete subject distance obtained in the previous step. Thereby, the focus correction amounts (ac) corresponding to the coordinates CxCy1 to CxCy3 of the color evaluation values Cx and Cy shown in FIG. 6 are obtained.

Next, a focus position correction amount for the color evaluation value calculated by the color information detection unit 110 is calculated.
In the present embodiment, the color information detection unit 110 performs predetermined processing on the color signals R, G1, G2, and B constituting the digital image data from the A / D converter 104, as described as the processing in step S309. A color evaluation value Cx, Cy, Yi is calculated by performing calculation. Here, the color evaluation value is obtained by the following calculation.
Cx = {(R + G2)-(B + G1)} / Yi
Cy = {(R + B) / 4- (G1 + G2) / 4} / Yi
Yi = (R + G1 + G2 + B) / 4

  Since the distance measurement area usually includes a plurality of pixels, when calculating the color evaluation value, the luminance value is averaged for a set of R, G1, G2, and B pixels included in the distance measurement area, and the average value is calculated for each average value. The color evaluation value can be obtained by applying the above formula.

  As shown in FIG. 8, the position correction amount corresponding to the calculated color evaluation value can be calculated by interpolating a plurality of stored values having a small distance from the color evaluation value on the CxCy plane, or by using the smallest distance. It can be calculated as a stored value. When performing the interpolation, there is no particular limitation on the method, and a known method such as bilinear interpolation or bicubic interpolation can be suitably used.

For example, in the example shown in FIG. 8, the in-focus position correction amount corresponding to the coordinates of the color evaluation value obtained at the time of imaging is set as the in-focus position correction amount corresponding to CxCy1 to CxCy3 for which the in-focus position correction amount has been calculated. It is calculated by interpolating from the quantities a to c.
In this way, the final focus position correction amount is calculated in consideration of the subject distance, subject color, and ranging area position.

<AF processing>
Next, the AF process including the focus position correction as described above will be described with reference to the flowchart shown in FIG. This process is performed in step S310 in FIG. As described above, in the present embodiment, the in-focus position is determined by detecting a peak of a high-frequency component (hereinafter referred to as a focus evaluation value) of a signal obtained from the image sensor 103.

  First, in step S <b> 601, the position correction amount calculation unit 114 reads a plurality of correction tables corresponding to the zoom position and the aperture value obtained from the imaging lens state detection unit 109 from the storage unit 113. Then, the position correction amount corresponding to the current distance measurement position is obtained for a plurality of discrete subject distances using the image height of the set distance measurement position and each correction table.

  In step S603, the focus lens 102 is moved to the scan start position. Here, it is assumed that the scan start position is set to an infinite end in the distance measurement range. In subsequent step S <b> 605, the extraction unit 111 extracts a signal indicating a high-frequency component of a pixel included in the distance measurement area of the digital image data, and outputs the signal to the in-focus position detection unit 112. Then, the focus position detection unit 112 associates the signal (focus evaluation value) extracted by the extraction unit 111 with the position of the focus lens 102 at that time, and stores it in a predetermined area of the correction amount storage unit 113, for example.

  In step S607, it is checked whether or not the focus lens 102 is at the end position. If it is the end position, the process proceeds to step S609. Otherwise, the process proceeds to step S615. Here, the scan end position is set to the closest end in the distance measurement range. In step S615, the focus lens drive control unit 115 moves the focus lens 102 by a predetermined amount in the closest direction, and the process returns to step S605.

  If the focus lens 102 has reached the end position, the focus position detection unit 112 detects the position of the focus lens 102 corresponding to the maximum focus evaluation value from the stored data in step S609, and the subject distance from the lens position. Is calculated. The calculated subject distance is notified to the position correction amount calculation unit 114.

  In step S611, the position correction amount calculation unit 114 calculates a correction amount obtained from a correction table corresponding to a distance shorter than the calculated subject distance among the plurality of correction amounts obtained in step S601 and a correction table corresponding to a long distance. The correction amount obtained from the above is detected. These two sets of correction amounts are preferably correction amounts obtained from a correction table corresponding to a distance closest to the calculated subject distance. Then, a position correction amount (ac in FIG. 7) corresponding to the current subject distance is calculated by interpolating from these correction values.

  In step S612, the position correction calculation unit 114 calculates final focus position correction amounts corresponding to the color evaluation values Cx and Cy of the distance measurement area detected by the color information detection unit 110 in step S309. That is, using the relationship between the color evaluation value detected by the color information detection unit 110 and the color evaluation values corresponding to the plurality of correction amounts obtained in step S611, it corresponds to the color evaluation value detected by the color information detection unit 110. The final focus position correction amount is calculated (FIG. 8).

  In step S613, the position correction calculation unit 114 inputs the focus position correction amount calculated in step S612 to the focus lens drive control unit 115, and corrects the position of the focus lens 102.

<Details of shooting operation>
Finally, the photographing operation in step S313 in FIG. 11 will be described with reference to the flowchart in FIG.
First, in step S701, the subject brightness is measured, and in the next step 702, the image sensor 103 is exposed according to the subject brightness measured in step S701. In subsequent step S703, output noise removal of the image sensor 103 and non-linear processing performed before A / D conversion are performed by a pre-processing circuit (not shown), and in step S704, the image data is converted into digital image data by the A / D converter 104. .

  In step S <b> 705, output data from the A / D converter 104 is temporarily stored in the temporary storage unit 106. In step S706, the image processing unit 107 performs image processing such as color interpolation processing, white balance processing, and compression encoding processing on the data in the temporary storage unit 106, and then the recording unit 108 records data such as a memory card. Transfer to media.

  As described above, according to the present embodiment, focusing accuracy is further improved by correcting chromatic aberration of the imaging optical system in consideration of not only the color information of the subject but also the subject distance and the distance measurement area position. It becomes possible to make it. The correction amount storage unit 113 stores in-focus position correction amounts for a plurality of combinations of depth of field and color information in the captured image, and the imaging optical system also takes into account the depth of field. The chromatic aberration can be corrected. In this case, the focusing accuracy can be further improved.

<Second Embodiment>
FIG. 2 is a block diagram illustrating a configuration example of an imaging apparatus according to the second embodiment of the present invention.
2, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
The imaging apparatus according to the present embodiment does not include the ranging area signal extraction unit 116, and the output signal of the A / D converter 104 is input to the color information detection unit 110 and the extraction unit 111, and the in-focus position detection unit 112 and the position. A difference from the first embodiment is that a ranging area position determination unit 117 is provided between the correction amount calculation units 114.

  A signal (focus position information) detected by the focus position detection unit 112 is input to the distance measurement region position determination unit 117. For example, as shown in FIG. 9, the distance measurement area position determination unit 117 uses a predetermined distance measurement position extraction condition such as distance information of a subject from a plurality of predetermined distance measurement positions (distance measurement candidate positions). Determine the distance measurement position. Information regarding the determined distance measurement position is supplied to the color information detection unit 110. Further, the focus position information from the focus position detection unit 112 is supplied to the position correction amount calculation unit 114 via the distance measurement region position determination unit 117.

  As in the first embodiment, the correction amount storage unit 113 is in focus corresponding to a plurality of combinations of color evaluation values Cx, Cy and ranging area positions for each of a plurality of combinations of zoom position, aperture value, and subject distance. A correction table in which position correction amounts are associated is stored. However, in the present embodiment, as shown in FIG. 9, since the distance measurement area position candidates are determined in advance, the focus position correction amount may be stored for each candidate position.

  In particular, when ranging area candidates are determined symmetrically as shown in FIG. 9, the ranging area candidate (1) having the same distance from the center of the image plane (image height) is the same. The correction amount may be stored for each of the groups (ranging areas (2) and (3)).

  FIG. 10 is a diagram schematically showing the contents of the correction table stored in the correction amount storage unit 113 when the distance measurement area is set as shown in FIG. 9, which is the same as FIG. 5 in the first embodiment. Correspond. Although each correction table stores nine values in common, it is not necessary to obtain a correction value corresponding to the image height at the time of shooting by interpolation, so the horizontal axis is not the image height but the group number of the distance measurement area. Is different.

  The position correction amount calculation unit 114 uses a plurality of correction tables corresponding to the current zoom position and aperture value, and is determined by the distance measurement region position determination unit 117 for each table (that is, for each discrete subject distance). A correction value corresponding to the group to which the ranging area belongs is acquired. As a result, focus correction amounts for combinations of three color evaluation values are obtained for each of a plurality of discrete subject distances. The subsequent processing is the first except that the color information detection unit 110 calculates the color evaluation value of the distance measurement area in the image based on the position information of the distance measurement area notified from the distance measurement area position determination unit 117. As described in the embodiment.

  In the present embodiment, the ranging area position determination unit 117 automatically determines the ranging area, but the same processing is performed even when the user presets each ranging area shown in FIG. Is possible. In this case, the distance measurement area position determination unit 117 may acquire the position information of the set candidate area, and other processes need not be changed.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, when the position of the ranging area is selected from a plurality of positions determined in advance, the calculation processing of the focus position correction amount is performed. In addition, the storage capacity of the correction amount storage unit 113 can be saved.

<Other embodiments>
In the above-described embodiment, the case where the imaging lens 101 is a zoom lens that is a multifocal length lens has been described. However, in the case of a single focus lens, a correction table corresponding to a plurality of discrete distances for each aperture value. Should be memorized. The correction table to be used is also detected using only the aperture value.

  Furthermore, the subject distance is not limited to the method of obtaining from the position of the focus lens 102, and for example, another mechanism for detecting the subject distance may be provided. In this case, when the subject distance is necessary in the above-described processing, it is obtained from this mechanism. As such a distance measuring mechanism, for example, a mechanism that emits light or ultrasonic waves, detects the reflected wave, and measures the distance can be used.

  In the above embodiment, the focus control depending on the contrast according to the output from the so-called image sensor has been described. However, the present invention is not limited thereto, and the signal at the time of focus control is a signal before the development processing by the image processing unit 107. If the difference between the color visually perceived by humans and the signal subjected to photoelectric conversion as the focus signal is generated, the technique described in the present embodiment can be used even for phase difference AF, for example. be able to.

  Further, the distance measuring mechanism may be an external device. Similarly, in addition to obtaining the color information of the subject from the pixels in the distance measuring area of the image sensor, the color information of the subject may be obtained by an external device capable of measuring the color information, and the result may be used. Further, a sensor for detecting color information may be separately provided in the imaging apparatus.

  Note that a software program that realizes the functions of the above-described embodiments is supplied from a recording medium to an imaging apparatus having a computer that can execute the program directly or using wired / wireless communication, and the imaging apparatus supplies the software program. The present invention also includes a case where an equivalent function is achieved by executing the programmed program.

  Accordingly, since the functions of the present invention are implemented by a computer included in an imaging apparatus having an automatic focusing function, the program code supplied and installed in the computer also implements the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  As a recording medium for supplying the program, for example, a magnetic recording medium such as a flexible disk, a hard disk, a magnetic tape, MO, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD- There are optical / magneto-optical storage media such as RW, and non-volatile semiconductor memory.

  As a program supply method using wired / wireless communication, when the imaging apparatus has a connection function with a computer network, the computer program itself that forms the present invention in a server on the computer network, or a compressed automatic installation function A method of storing a data file (program data file) that can be a computer program forming the present invention in the imaging apparatus, such as a file including a file, and downloading the program data file to a connected imaging apparatus. In this case, the program data file can be divided into a plurality of segment files, and the segment files can be arranged on different servers.

  In addition, the imaging apparatus and an external computer may be directly connected, and the software program constituting the present invention may be downloaded from the external computer to a nonvolatile memory in the imaging apparatus.

1 is a block diagram illustrating a configuration example of an imaging apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structural example of the imaging device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the example of a color arrangement | positioning of the color filter which an image sensor uses. It is a figure showing the visibility characteristic of a human eye. It is a figure for demonstrating the process of obtaining the correction amount according to the content of the correction table memorize | stored in the correction amount memory | storage part 113 in 1st Embodiment, and a ranging area position. It is a figure which shows the example of the discrete color evaluation value used for a correction table. It is a figure explaining the method of calculating | requiring the position correction amount corresponding to the to-be-measured object distance from the correction amount corresponding to discrete distance. It is a figure for demonstrating the process which calculates the final focus position correction amount according to the color evaluation value of a ranging area. It is a figure which shows the example of several ranging area. It is a figure for demonstrating the content of the correction table memorize | stored in the correction amount memory | storage part 113 in 2nd Embodiment, and the process which obtains the correction amount according to a ranging area position. 3 is a flowchart illustrating an overall operation of the imaging apparatus according to the embodiment of the present invention. It is a figure which shows the example of a ranging area and its display method. FIG. 10 is a diagram illustrating a specific example of a method for storing a zoom position and an aperture value in a correction table. 6 is a flowchart showing details of autofocus processing of the imaging apparatus according to the embodiment of the present invention. 4 is a flowchart illustrating a shooting operation of the imaging apparatus according to the embodiment of the present invention.

Claims (6)

An in-focus position detecting means for detecting an in-focus position of a focus lens for focus adjustment corresponding to a range-finding area set from an arbitrary position in a shooting screen or a predetermined plurality of positions;
Storage means for storing the in-focus position correction amount according to the color information of the subject and the position of the distance measurement area on the shooting screen;
An image pickup apparatus comprising: control means for controlling to correct the focus position of the focus lens using the focus position correction amount stored in the storage means.   The imaging apparatus according to claim 1, wherein the focus position detection unit detects a focus position based on a magnitude of a high-frequency component of a pixel included in the distance measurement area. Subject distance acquisition means for acquiring a subject distance based on the position of the focus lens corresponding to the focus position detected by the focus position detection means;
3. The imaging apparatus according to claim 1, wherein the control unit performs control so as to correct a focus position of the focus lens in accordance with the subject distance acquired by the subject distance acquisition unit. .   The control unit acquires color information of a subject based on a pixel signal included in the distance measurement area, and uses a focus position correction amount corresponding to the acquired color information to adjust a focus position of the focus lens. The imaging apparatus according to any one of claims 1 to 3, wherein control is performed so as to correct. The imaging optical system includes a multifocal length lens,
5. The storage unit according to claim 1, wherein the storage unit stores the in-focus position correction amount for each combination of a focal length and an aperture value that can be taken by the multifocal length lens. The imaging device described. An in-focus position detecting means for detecting an in-focus position of a focus lens for focus adjustment corresponding to a range-finding area set from an arbitrary position in a shooting screen or a predetermined plurality of positions;
Control means for controlling to correct the in-focus position of the focus lens using the in-focus position correction amount corresponding to the color information of the subject and the position of the ranging area on the shooting screen. Focus adjustment device.

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