JP2023067973A - interchangeable lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interchangeable lens capable of sending information on magnification chromatic aberration to a camera body.

SOLUTION: An interchangeable lens attachable to a camera body is provided, comprising: a storage unit configured to store information on a coefficient of a function representing magnification chromatic aberration of an optical system, approximated using at least either of a shooting distance and a focal length; and a transmission unit configured to transmit the information on the coefficient stored in the storage unit to the camera body.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to an interchangeable lens.

2. Description of the Related Art An imaging apparatus is known that detects color shift due to chromatic aberration of magnification from image data and corrects the color shift (Patent Document 1). However, there are cases where color misregistration cannot be detected from the image data depending on the pattern, or erroneous detection occurs and correct correction is not performed, resulting in deterioration of the image quality of the image.

Japanese Unexamined Patent Application Publication No. 2012-23532

According to a first aspect of the present invention, the interchangeable lens is an interchangeable lens that can be attached to a camera body, and is a function representing the chromatic aberration of magnification of the optical system approximated using at least one of the shooting distance and the focal length. An interchangeable lens, comprising: a storage unit that stores information about coefficients; and a transmission unit that transmits information about the coefficients stored in the storage unit to the camera body.

1 is a block diagram showing the configuration of an imaging device according to a first embodiment; FIG. It is a figure which shows an example of the color shift amount which arises by a magnification chromatic aberration. It is a figure which shows an example of the function showing chromatic aberration of magnification. 4 is a table showing coefficients of a function representing chromatic aberration of magnification; 4 is a table showing coefficients of a function representing chromatic aberration of magnification; FIG. 5 is a diagram schematically showing a curved surface that approximates coefficients of a function representing chromatic aberration of magnification; 4 is a flow chart showing an operation example of the imaging device according to the first embodiment;

(First embodiment)
FIG. 1 is a diagram showing a configuration example of a camera 1, which is an example of an imaging device according to the first embodiment. A camera 1 is composed of a camera body 2 and an interchangeable lens 3 as an attachable accessory.

The camera body 2 is provided with a body-side mount section 201 to which the interchangeable lens 3 is attached. The interchangeable lens 3 is provided with a lens-side mount section 301 attached to the camera body 2 . A lens side connection portion 302 and a body side connection portion 202 are provided on the lens side mount portion 301 and the body side mount portion 201, respectively. The lens side connection portion 302 and the body side connection portion 202 are each provided with a plurality of terminals such as terminals for clock signals, terminals for data signals, and terminals for power supply. The interchangeable lens 3 is detachably attached to the body side mount portion 201 of the camera body 2 by the lens side mount portion 301 . Note that the camera 1 may be a camera in which the camera body 2 and the lens portion 3 are integrally configured (lens fixed camera).

When the interchangeable lens 3 is attached to the camera body 2, the terminals provided on the body-side connecting portion 202 and the terminals provided on the lens-side connecting portion 302 are electrically connected. This enables power supply from the camera body 2 to the interchangeable lens 3 and communication between the camera body 2 and the interchangeable lens 3 .

The interchangeable lens 3 includes a photographing optical system (imaging optical system) 31 , a lens control section 32 and a lens memory 33 . The interchangeable lens 3 is, for example, a zoom lens. The photographing optical system 31 includes a plurality of lenses including a lens (magnifying lens) 31a for changing the focal length and a focus lens (focusing lens) 31b, and an aperture 31c. form an image.

The lens control unit 32 includes a processor such as CPU, FPGA, and ASIC, and memory such as ROM and RAM, and controls each unit of the interchangeable lens 3 based on a control program. The lens control section 32 drives the lens 31a, the focus lens 31b, and the diaphragm 31c based on signals input from the body control section 22 of the camera body 2 via the body side connection section 202 and the lens side connection section 302. Control.

For example, when a signal indicating the moving direction, moving amount, moving speed, etc. of the focus lens 31b is input from the body control unit 22, the lens control unit 32 advances and retreats the focus lens 31b in the direction of the optical axis L based on the signal. By moving it, the imaging position of the subject image formed by the photographing optical system 31 is changed. Further, the lens control section 32 controls the position of the lens 31a and the aperture diameter of the diaphragm 31c based on the signal output from the body control section 22 of the camera body 2. FIG.

The lens memory 33 is composed of, for example, a non-volatile storage medium. Information related to the interchangeable lens 3 is stored in the lens memory 33 . In the present embodiment, the lens memory 33 stores information about coefficients of functions representing the chromatic aberration of magnification of the imaging optical system 31 as chromatic aberration of magnification information. Writing data to the lens memory 33 and reading data from the lens memory 33 are controlled by the lens controller 32 . Note that the magnification chromatic aberration information may be stored in a memory inside the lens control section 32, or may be stored in a body memory 23 (or a memory inside the body control section 22), which will be described later.

After the interchangeable lens 3 is attached to the camera body 2 , the lens control section 32 transmits magnification chromatic aberration information to the body control section 22 via the lens side connection section 302 and the body side connection section 202 . That is, the lens control unit 32 functions as a transmission unit that transmits information regarding the chromatic aberration of magnification of the imaging optical system 31 to the camera body 2 , and the body control unit 22 transmits information regarding the chromatic aberration of magnification of the imaging optical system 31 from the interchangeable lens 3 . It functions as a receiver for receiving. In addition, the lens control unit 32 transmits position information (focal length information) of the controlled lens 31a, position information of the controlled focus lens 31b, information of the aperture value (F value) of the controlled diaphragm 31c, and the like to the body control unit. 22.

Next, the configuration of the camera body 2 will be described. The camera body 2 includes an imaging device 21 , a body control section 22 , a body memory 23 , a display section 24 and an operation section 25 .

The imaging element 21 is, for example, a CMOS image sensor or a CCD image sensor. The imaging device 21 receives the light flux that has passed through the imaging optical system 31 and captures an image of the subject. In the imaging device 21, a plurality of pixels each having a photoelectric conversion unit are arranged two-dimensionally (for example, row direction and column direction). The photoelectric conversion unit is composed of, for example, a photodiode (PD). The imaging element 21 photoelectrically converts the received light to generate a signal. The signal generated by the imaging device 21 is output from the imaging device 21 to the body control section 22 as image data (image signal).

The body memory 23 is composed of, for example, a non-volatile storage medium or the like. Image data and the like are recorded in the body memory 23 . Writing data to the body memory 23 and reading data from the body memory 23 are controlled by the body control unit 22 . The display unit 24 displays an image based on image data, information related to shooting such as shutter speed and aperture value, a menu screen, and the like. The operation unit 25 includes various setting switches such as a release button, a power switch, and switches for switching various modes, and outputs operation signals corresponding to respective operations to the body control unit 22 .

The body control section 22 includes a processor such as a CPU and FPGA, and a memory such as ROM and RAM, and controls each section of the camera 1 based on a control program. The body control section 22 generates signals for controlling driving of the lens 31a, the focus lens 31b, and the diaphragm 31c, and outputs the generated signals to the lens control section 32. FIG. Also, the body control unit 22 performs image processing on the image data output from the imaging device 21 . Image processing includes, for example, known image processing such as tone conversion processing, color interpolation processing, edge enhancement processing, and the like.

The body control unit 22 according to the present embodiment performs correction processing on the image data output from the imaging element 21 using the above-described chromatic aberration of magnification information, and generates image data with reduced color shift due to chromatic aberration of magnification. . The chromatic aberration of magnification information used when correcting color shift due to chromatic aberration of magnification will be described below.

Even if the light is from the same subject, light of different wavelengths (bands) such as R (red), G (green), and B (blue) form images at different positions on the imaging device 21 due to chromatic aberration of magnification. Since the light from the subject forms an image at different image heights depending on the wavelength, the subject images formed by the light of each wavelength of R, G, and B have different image sizes, that is, different image magnifications. become. Therefore, the image data obtained by imaging the subject image by the imaging optical system 31 is affected by the chromatic aberration of magnification caused by the imaging optical system 31, and color shift occurs.

FIG. 2 is a diagram showing an example of the amount of color shift caused by chromatic aberration of magnification. In FIG. 2, the horizontal axis is the image height (in units of mm, for example), and the vertical axis is the amount of deviation from the reference color component (in units of, for example, mm). In the example shown in FIG. 2, the G component among the color components (R component, G component, and B component) of the image data is used as a reference, waveform 41 indicates the amount of deviation between the G component and the R component, and waveform 42 indicates the amount of deviation between the G component and the R component. It shows the amount of deviation between the G component and the B component. The amount of color shift increases as the image height increases, as shown in FIG. 2, for example.

The chromatic aberration of magnification of the imaging optical system 31 can be expressed by a function expression in which the distance from the optical axis L of the imaging optical system 31 is a variable. In this embodiment, the value of the chromatic aberration of magnification is represented by a function LCR(r) whose variable is an image height ratio r (=image height/maximum image height), which is the ratio of the image height to the maximum image height. Here, the maximum image height represents the maximum image height on the imaging surface of the imaging device 21 . Also, let r0 be the image height ratio corresponding to the position of the signal to be corrected in the image data, and let r1 be the image height ratio corresponding to the post-correction position of the correction target signal. An image height ratio r0 represents a pixel position before correction in the image sensor 21, and an image height ratio r1 represents a pixel position in the image sensor 21 after correction. In this case, the relationship between the image height ratio r0 before color shift correction and the image height ratio r1 after correction can be expressed as follows using LCR(r).
r0=r1×(1+LCR(r1)) (1)

For example, when position correction of the R component and the B component is performed with the G component of each color component (R component, G component, and B component) of the image data as a reference, the image height ratio r0 in the above equation (1) is , indicates the image height corresponding to the position of the signal of the R component or B component on the sensor (image sensor 21) before correction, that is, the image height ratio r1 indicates the R component or after correction of the chromatic aberration of magnification. The image height corresponding to the position of the B component signal is shown. LCR(r) is a function relating to the positional ratio of images of different color components, for example, the ratio of the position of the G component to the position of the R component or the B component, and represents the amount of magnification for correcting color misregistration. It can also be said. The function LCR(r) changes according to the magnitude of the amount of color shift due to chromatic aberration of magnification, and even with the same focal length and photographing distance, the function LCR(r) has different values for different types of lenses.

A function LCR(r) representing the chromatic aberration of magnification can be expressed, for example, by the following equation (2).
LCR(r)=a+br ² +cr ³ (2)
In this equation (2), the coefficient a is the coefficient of the 0th order term of the image height ratio r, the coefficient b is the coefficient of the second order term of the image height ratio r, and the coefficient c is the 3rd order term of the image height ratio r. is the coefficient of the next term. In the function expression (2) having the image height ratio r as a variable, a is a constant term. The function LCR(r) changes according to the image height ratio r, and is as shown in FIG. 3, for example. The coefficients a, b, and c change according to the lens arrangement of the imaging optical system 31, respectively. In other words, the amount of color shift due to chromatic aberration of magnification varies depending on the lens position (focal length and photographing distance) of the lens used for photographing, in addition to the wavelength of light and image height. In the case of a zoom lens, the amount of color shift changes depending on both the focal length and the shooting distance, and in the case of a single focus lens, the amount of color shift changes depending on the shooting distance.

Although the coefficients a, b, and c change when the focal length and shooting distance are changed, they can be determined in advance by performing simulations using design data of the lens used for photography and experiments using actual lenses. be able to. As a result of simulations and the like, the inventors found that the zeroth-order, second-order, and third-order terms of the image height ratio r can be corrected using the above equations (1) and (2). It has been found that the approximation formula with a small number of terms can accurately correct the color shift caused by the chromatic aberration of magnification. In the following, as an example, a case where the focal length f and the shooting distance d are changed in five ways and 25 coefficients a, b, and c are obtained by simulation using design data will be described.

FIG. 4 is a table showing the coefficients of the function representing the chromatic aberration of magnification in the camera 1 according to the first embodiment. FIG. 4 shows the coefficients a, b, and c when the focal length is changed in five ways from f1 to f5 and the photographing distance is changed in five ways from d1 to d5. For example, when the focal length is f1 and the shooting distance is d1, the coefficients a, b, and c are a11, b11, and c11, respectively. FIG. 5 shows only the coefficient a among the coefficients a (a11 to a55), the coefficients b (b11 to b55), and the coefficients c (c11 to c55).

・・・（３）
なお、式（３）において、ｆｒはレンズに固有の最短焦点距離であり、ａ（ｆ）は最短焦点距離ｆｒの焦点距離ｆに対する比（ｆｒ／ｆ）を変数とする関数となる。（ｆｒ／ｆ）は、正規化された値となり、１以下の値を取り得る。 In FIG. 5, for example, by referring to the coefficients a11, a12, a13, a14, and a15 when the photographing distance is d1, it is possible to grasp the change of the coefficient a due to the focal length f when the photographing distance is d1. . Therefore, by performing calculations using these coefficients a11, a12, a13, a14, and a15, it is possible to approximate with a curve the coefficient a that changes according to the focal length f when the shooting distance is d1. For example, a function a(f) representing a coefficient a that varies depending on the focal length f is expressed by the following equation (3).

... (3)
In equation (3), fr is the shortest focal length unique to the lens, and a(f) is a function whose variable is the ratio (fr/f) of the shortest focal length fr to the focal length f. (fr/f) is a normalized value and can take a value of 1 or less.

・・・（４）
なお、式（４）において、ｄｒは交換レンズ（ズームレンズ）３の最短撮影距離であり、ａ（ｄ）は最短撮影距離ｄｒの撮影距離ｄに対する比（ｄｒ／ｄ）を変数とする関数となる。（ｄｒ／ｄ）は、正規化された値となり、０から１の値を取り得る。 Further, for example, by referring to the coefficients a11, a21, a31, a41, and a51 when the focal length is f1, the change in the coefficient a when the shooting distance d is changed when the focal length is f1 can be grasped. be able to. Therefore, by performing calculations using these coefficients a11, a21, a31, a41, and a51, it is possible to approximate with a curve the coefficient a that changes according to the photographing distance d when the focal length is f1. For example, the function a(d) representing the coefficient a that changes depending on the shooting distance d is expressed by the following equation (4).

... (4)
In equation (4), dr is the shortest shooting distance of the interchangeable lens (zoom lens) 3, and a(d) is a function whose variable is the ratio (dr/d) of the shortest shooting distance dr to the shooting distance d. Become. (dr/d) is a normalized value and can take values from 0 to 1.

・・・（５） Furthermore, if the above-described method is extended, the coefficient a can be approximated by a curved surface. For example, the function a(f, d) representing the coefficient a that changes according to the focal length f and the photographing distance d is expressed by the following equation (5).

... (5)

This formula (5) consists of 12 terms obtained by combining the above formulas (3) and (4). By using Equation (5), the coefficient a can be approximated by a curved surface as in the example shown in FIG. That is, Equation (5) is an approximation model for estimating the coefficient a. The 12 coefficients (A ₀₀ to A ₃₂ ) in equation (5) are calculated based on the 25 coefficients a11 to a55 shown in FIG. Specifically, by fitting the coefficients (A ₀₀ to A ₃₂ ) in the equation (5) so that the error with the 25 coefficients a11 to a55 is small, the 12 coefficients in the equation (5) are Values for the coefficients A ₀₀ to A ₃₂ are selected.

・・・（６） Similarly, the function b(f) representing the coefficient b that changes according to the focal length f is expressed by the following equation (6) by calculating using the coefficients b11 to b15 shown in FIG. 4, for example.

... (6)

・・・（７） Also, the function b(d) representing the coefficient b that changes according to the shooting distance d is expressed by the following equation (7) by performing calculations using the coefficients b11 to b51, for example.

... (7)

・・・（８） Furthermore, the function b(f,d) representing the coefficient b that changes according to the focal length f and the shooting distance d is obtained by performing calculations using 25 pieces of data for the coefficient b (coefficients b11 to b55) as follows: It is represented by Formula (8).

... (8)

・・・（９） Also, the function c(f) representing the coefficient c that changes according to the focal length f is expressed by the following equation (9) by calculating using the coefficients c11 to c15 shown in FIG. 4, for example.

... (9)

・・・（１０） A function c(d) representing a coefficient c that changes according to the shooting distance d is expressed by the following equation (10) by performing calculations using coefficients c11 to c51, for example.

(10)

・・・（１１） Further, the function c(f,d) representing the coefficient c that changes according to the focal length f and the shooting distance d is obtained by performing calculations using 25 pieces of data (coefficients c11 to c55) of the coefficient c, as follows: It is represented by Formula (11).

(11)

As described above, the 12 coefficients A ₀₀ -A ₃₂ that approximate the coefficient a, the 12 coefficients B ₀₀ -B ₃₂ that approximate the coefficient b, and the 12 coefficients C ₀₀ -C ₃₂ that approximate the coefficient c A total of 36 coefficients (approximate coefficients) are calculated. Information on these approximation coefficients is stored in the lens memory 33 of the interchangeable lens 3 as the above-described magnification chromatic aberration information. That is, the lens memory 33 stores the chromatic aberration of magnification information regarding the coefficients a, b, and c of the functional expression (2) representing the chromatic aberration of magnification of the imaging optical system 31 .

Further, the amount of color shift is not only caused by the chromatic aberration of magnification, but also affected by spherical aberration and other chromatic aberrations, and thus varies depending on the aperture value of the diaphragm 31c. Therefore, the above 36 approximation coefficients (coefficients A ₀₀ to A ₃₂ , B ₀₀ to B ₃₂ , C ₀₀ to C ₃₂ ) are calculated for a plurality of aperture values and stored in the lens memory 33 . For example, the lens memory 33 stores information on 36 approximation coefficients for the first aperture value and information on 36 approximation coefficients for the second aperture value. It should be noted that 36 approximation coefficients may be calculated for the number of stops and stored in the lens memory 33 in advance.

Further, in the present embodiment, in order to correct each of the color shift between the G component and the R component and the color shift between the G component and the B component, the amount of color shift between the G component and the R component is estimated. and information of approximation coefficients for estimating the amount of color shift between the G component and the B component are stored in the lens memory 33, respectively.

The chromatic aberration of magnification information stored in the lens memory 33 is transmitted from the interchangeable lens 3 to the camera body 2 at arbitrary timing, for example, in initial communication after the interchangeable lens 3 is attached to the camera body 2 . Further, the information of formulas (1) and (2) described above is stored in the internal memory of the body control section 22 .

The body control unit 22 calculates LCR(r) based on the formula (2) described above, the magnification chromatic aberration information transmitted from the interchangeable lens 3, and the lens position information at the time of shooting. Further, the body control unit 22 calculates the amount of color shift due to the chromatic aberration of magnification using the above-described formula (1) and the calculated LCR(r), and corrects the image data based on the calculated amount of color shift. Specifically, the body control unit 22 performs a process of correcting the image data so as to obtain image data of each pixel when an image is captured by the imaging optical system 31 without chromatic aberration of magnification. For example, the body control unit 22 performs processing for converting the coordinates of the image data based on the calculated amount of color misregistration. More specifically, the body control unit 22 shifts the R component signal so that the amount of deviation between the G component and the R component is reduced, and shifts the signal of the B component so that the amount of deviation between the G component and the B component is decreased. A correction process is performed to shift the signal of Thereby, the body control unit 22 can generate image data in which color shift due to chromatic aberration of magnification is reduced.

FIG. 7 is a flow chart showing an operation example of the camera 1 of this embodiment. An operation example of the camera 1 will be described with reference to the flowchart of FIG.

In step S100, the body control unit 22 of the camera body 2 transmits a signal requesting transmission of magnification chromatic aberration information to the interchangeable lens 3, for example, after power is turned on. In step S<b>200 , the lens control unit 32 of the interchangeable lens 3 receives a request signal for lateral chromatic aberration information from the camera body 2 .

In step S<b>210 , the lens control unit 32 transmits the magnification chromatic aberration information stored in the lens memory 33 or the like to the camera body 2 . That is, as described above, the lens control unit 32 sends the information of the approximation coefficients (coefficients A ₀₀ to A ₃₂ , B ₀₀ to B ₃₂ , C ₀₀ to C ₃₂ ) acquired for a plurality of aperture values to the camera body 2. Send to In step S<b>110 , the body control section 22 receives the information of the approximation coefficient from the interchangeable lens 3 and stores it in the internal memory of the body control section 22 .

In step S120, when the release operation is performed by the operation unit 25, the body control unit 22 causes the imaging device 21 to pick up a subject image and output image data. Further, in step S220, the lens control unit 32 transmits information (state information) regarding the state of the photographing optical system 31 at the time of release to the camera body 2. FIG. This state information includes, for example, focal length information, shooting distance information, and aperture value information. Specifically, the lens control unit 32 transmits the above-described normalized values (fr/f), (dr/d), and the number of aperture steps to the camera body 2 as information on the focal length and the shooting distance. This state information may be repeatedly sent to the camera body 2 periodically or each time its value changes.

In step S130, the body control unit 22 refers to the approximation coefficient in the case of the aperture value at the time of imaging based on the transmitted state information and approximation coefficient information, and calculates the function a(f , d), the function b(f, d) in equation (8), and the function c(f, d) in equation (11). Also, the body control unit 22 substitutes the focal length f and the shooting distance d at the time of imaging into these equations (5), (8), and (11) to calculate the coefficients a, b, and c. Also, the calculated coefficients a, b, and c are substituted into the above equation (2) to determine the function LCR(r).

In step S140, the body control unit 22 performs color misregistration correction processing on the image data output from the image sensor 21 based on the function LCR(r) and the image height ratio r, as described above. In this manner, body control unit 22 according to the present embodiment generates image data in which color shift due to chromatic aberration of magnification is reduced.

According to the embodiment described above, the following effects are obtained.
(1) The interchangeable lens 3 is an interchangeable lens 3 that can be attached to the camera body 2, and is a function LCR(r) representing the lateral chromatic aberration of the optical system 31 approximated using at least one of the shooting distance and the focal length. a storage unit (e.g., lens memory 33) that stores information about the coefficients of Prepare. With this configuration, the camera body 2 refers to the approximation coefficient information transmitted from the interchangeable lens 3 to grasp the amount of color shift due to the chromatic aberration of magnification at all non-discrete lens positions. Image data with reduced color shift can be generated. As a result, deterioration in image quality can be suppressed.

(2) Function LCR(r) has an image height ratio r, which is the ratio of the image height to the maximum image height, as a variable. In the present embodiment, the amount of color shift due to chromatic aberration of magnification is expressed using a functional expression LCA(r) of the image height ratio r. Therefore, the amount of color shift can be represented by information that does not depend on the pixel pitch (interval between pixels), which is information specific to the image sensor 21, and correction processing can be performed efficiently by using this LCA(r). It becomes possible.

(3) The function LCR(r) represents the positional ratio of images of mutually different color components with a cubic term of the image height ratio r, a quadratic term of the image height ratio r, and a constant term. The storage unit stores the coefficient of the cubic term, the coefficient of the quadratic term, and the constant of the constant term as the information about the coefficient. In the present embodiment, the function LCR(r) consists of a cubic term, a quadratic term, and a 0th-order term of the image height ratio r. Since this is done, the amount of color shift due to chromatic aberration of magnification can be expressed with a small number of terms with high accuracy. The lens memory 33 also stores information of approximate coefficients (coefficients A ₀₀ to A ₃₂ , B ₀₀ to B ₃₂ , C ₀₀ to C ₃₂ ) that approximate the coefficients a, b, and c of these three terms. . Therefore, the amount of data stored in the lens memory 33 can be reduced. In addition, it is possible to reduce the amount of calculation when performing the color misregistration correction process.

(4) The coefficients a, b, and c of the function LCR(r) are the ratio (fr/f) of the shortest focal length fr to the focal length f, and the ratio (dr/d) of the shortest shooting distance dr to the shooting distance d. It is a coefficient approximated by a function with variables. In this embodiment, when the interchangeable lens 3 notifies the camera body 2 of the focal length and shooting distance information, the normalized values (fr/f) and (dr/d) are sent to the camera body 2. Send. Therefore, it is possible to notify the camera body 2 of the lens position (focal length information and shooting distance information) required for correction by fixed bit length data that is not affected by the focal length of the lens used. As a result, the amount of data transmitted from the interchangeable lens 3 to the camera body 2 can be reduced.

The following modifications are also within the scope of the present invention, and it is also possible to combine one or more of the modifications with the above-described embodiments.

(Modification 1)
In the above-described embodiment, an example in which the function LCR(r) is represented by three terms has been described. However, it may be represented by one term consisting of only 0th-order components, two terms, or four or more terms. Further, for example, LCR(r) may be represented by three terms of the image height ratio r, ie, a second-order term, a first-order term, and a zero-order term.

(Modification 2)
In the above-described embodiment, the coefficients a, b, and c of the function LCR(r) are approximated by functions whose variables are the focal length and the shooting distance. However, the coefficients a, b, and c may be approximated by a function having only one of the focal length and the shooting distance as a variable. For example, when the interchangeable lens 3 is a single-focus lens, the coefficients a, b, and c may be represented by functions with the shooting distance as a variable.

(Modification 3)
In the above-described embodiment, the coefficients a, b, and c of the function LCR(r) are defined as the ratio of the shortest focal length fr to the focal length f (fr/f) and the ratio of the shortest shooting distance dr to the shooting distance d (dr An example of approximation by a function with /d) as a variable has been described. However, the coefficients a, b, and c may be approximated by functions whose variables are the reciprocal of the focal length f and the reciprocal of the photographing distance d.

(Modification 4)
In the embodiment described above, the lens control unit 32 of the interchangeable lens 3 transmits the normalized values (fr/f) and (dr/d) to the camera body 2 as the focal length and shooting distance information. . Instead of (fr/f), the lens control unit 32 may transmit integer information (f _info ) represented by the following equation (12) to the camera body 2 as focal length information. Also, the lens control unit 32 may transmit integer information (d _info ) represented by the following equation (13) to the camera body 2 as information on the shooting distance instead of (dr/d). In this case, (fr/f) and (dr/d) can each be restricted to n-bit fixed-length information, and the amount of information can be made suitable for aberration correction. Note that the bit depths of (f _info ) and (d _info ) may be changed.
f _info ≡int { ²ⁿ ×(fr/f)} (12)
d _info ≡int { ²ⁿ ×(dr/d)} (13)

(Modification 5)
In the flowchart shown in FIG. 7, in step S210, the interchangeable lens 3 transmits to the camera body 2 all pieces of approximation coefficient information obtained for a plurality of aperture values. Alternatively, however, the interchangeable lens 3 may transmit to the camera body 2 only the approximation coefficients related to the aperture value at the time of shooting.

(Modification 6)
In the flowchart shown in FIG. 7, the interchangeable lens 3 transmits all the information of the approximation coefficients to the camera body 2 in step S210. However, instead of this, the approximation coefficient, the lens position f, d, and the number of aperture steps in the interchangeable lens 3 are used to calculate the magnification aberration correction coefficients a, b, and c at the time of shooting, and the correction coefficients a, b, and c are calculated by the camera. It may be transmitted to the body 2.

(Modification 7)
In the above-described embodiment, an example of correcting color shift due to chromatic aberration of magnification has been described. In this modified example, the reduction in the signal value (pixel value) of the image signal (image data) due to the reduction in the amount of light in the periphery compared to the center of the optical axis is corrected. A function Vig(r) representing a value (peripheral light amount correction amount) used when correcting a decrease in pixel value due to a light amount decrease (dimming) can be expressed by the following equation (14), for example.
Vig(r)=ar ² +br ⁴ +cr ⁶ (14)
Vig(r) is a function relating to the ratio of the amount of light at the center of the optical axis to the amount of light at the position of the image height ratio r, and represents a correction amount for correcting a decrease in pixel value due to limb darkening. In this equation (14), the coefficient a is the coefficient of the second-order term of the image height ratio r, the coefficient b is the coefficient of the fourth-order term of the image height ratio r, and the coefficient c is the coefficient of the sixth order term of the image height ratio r. is the coefficient of the next term. The coefficients a, b, and c change according to the focal length, shooting distance, and number of aperture steps of the imaging optical system 31, respectively.

A plurality of coefficients (approximate coefficients) that respectively approximate the coefficients a, b, and c are calculated in the same manner as in the above-described embodiment. Information on these approximation coefficients is stored in the lens memory 33 of the interchangeable lens 3 (or the internal memory of the lens controller 32). That is, the lens memory 33 (or the internal memory of the lens control unit 32) stores information about the coefficients a, b, and c of the functional expression (14) representing the peripheral light amount correction amount of the imaging optical system 31. FIG.

The body control unit 22 uses the above equation (14), the information of the coefficients a, b, and c transmitted from the interchangeable lens 3, and the image height ratio r corresponding to the position of the signal to be corrected in the image data. Based on this, Vig(r) is calculated. By multiplying the signal to be corrected by the calculated Vig(r), the body control unit 22 can correct the image data so that the brightness becomes uniform. As a result, it is possible to obtain image data in which the decrease in pixel value due to the decrease in the amount of light is reduced.

(Modification 8)
The imaging devices described in the above embodiments and modifications may be applied to cameras, smartphones, tablets, cameras built into PCs, vehicle-mounted cameras, cameras mounted on unmanned aerial vehicles (drones, radio-controlled machines, etc.). good.

(Modification 9)
In the above-described embodiment and modifications, the image data is corrected by the imaging device, but the image data may be corrected by an external device (computer, tablet terminal, other camera, etc.). Image data correction processing may be performed in a camera system that includes an imaging device and an external device. An imaging device (for example, camera 1) stores information on coefficients a, b, and c at the time of imaging together with image data. After photographing, an external device (for example, a computer) performs correction processing as described above using the image data and coefficients a, b, and c information acquired from the imaging device. As a result, the camera system can generate image data in which color shift due to chromatic aberration of magnification and pixel value decrease due to decrease in light intensity are reduced. Note that data communication between the imaging device and the external device may be performed using a storage medium such as a memory card, wireless communication, or wired communication. The image processing apparatus may be configured by causing a computer (processor) to execute a program that performs processing based on the flowchart illustrated in FIG. The program can be supplied as computer program products in various forms, such as provision via a storage medium or communication line.

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Imaging device, 2... Camera body, 3... Interchangeable lens, 21... Imaging element, 22... Body control part, 31... Imaging optical system, 32... Lens control part, 33... Lens memory

Claims (1)

An interchangeable lens attachable to a camera body,
a storage unit that stores information about coefficients of a function that represents the chromatic aberration of magnification of an optical system approximated using at least one of a shooting distance and a focal length;
a transmission unit configured to transmit information about the coefficients stored in the storage unit to the camera body;
Interchangeable lens with

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