Interchangeable lens

Abstract

To provide an interchangeable lens for transmitting information regarding chromatic aberration of magnification to a camera body.SOLUTION: Provided is an exchangeable lens that can be mounted to a camera body, the exchangeable lens comprising a storage unit for storing coefficient information regarding the coefficient of a first function representing the chromatic aberration of magnification of an optical system, and a transmission unit for transmitting, to the camera body, the coefficient information and state information related to either the imaging distance or the focal length of the optical system. The coefficient information includes at least one of first information related to a coefficient approximated by a second function adopting the ratio of the shortest imaging distance to said imaging distance as a variable and second information related to a coefficient approximated by a third function adopting the ratio of the shortest focal length to said local length as a variable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an interchangeable lens. [Background technology]

[0002] An imaging device is known that detects color shift due to chromatic aberration of magnification from image data and corrects the color shift (Patent Document 1). However, depending on the image, color shift may not be detected from the image data or may be erroneously detected, resulting in incorrect correction and a decrease in image quality. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-23532 Summary of the Invention

[0004] According to a first aspect of the present invention, an interchangeable lens is an interchangeable lens that can be attached to a camera body, and comprises: a memory unit that stores coefficient information regarding the coefficient of a first function that represents the chromatic aberration of magnification of an optical system; and a transmitter unit that transmits to the camera body the coefficient information and status information regarding at least one of the shooting distance or focal length of the optical system, wherein the coefficient information includes at least one of first information regarding a coefficient approximated by a second function that has as a variable the ratio of the shortest shooting distance to the shooting distance, or second information regarding a coefficient approximated by a third function that has as a variable the ratio of the shortest focal length to the focal length. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a block diagram showing a configuration of an imaging device according to a first embodiment. [Figure 2] 10A and 10B are diagrams illustrating an example of the amount of color shift caused by chromatic aberration of magnification. [Figure 3] FIG. 10 is a diagram illustrating an example of a function representing chromatic aberration of magnification. [Figure 4]10 is a table showing coefficients of a function representing lateral chromatic aberration. [Figure 5] 10 is a table showing coefficients of a function representing lateral chromatic aberration. [Figure 6] FIG. 10 is a diagram schematically illustrating a curved surface that approximates the coefficients of a function that represents chromatic aberration of magnification. [Figure 7] 4 is a flowchart showing an example of the operation of the imaging device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] (First embodiment) 1 is a diagram showing an example of the configuration of a camera 1, which is an example of an imaging device according to the first embodiment. The camera 1 is made up of a camera body 2 and an interchangeable lens 3, which is an attachable accessory.

[0007] The camera body 2 is provided with a body-side mount unit 201 to which the interchangeable lens 3 is attached. The interchangeable lens 3 is provided with a lens-side mount unit 301 to be attached to the camera body 2. The lens-side mount unit 301 and the body-side mount unit 201 are provided with a lens-side connection unit 302 and a body-side connection unit 202, respectively. The lens-side connection unit 302 and the body-side connection unit 202 are each provided with multiple terminals such as a terminal for a clock signal, a terminal for a data signal, and a terminal for power supply. The interchangeable lens 3 is detachably attached to the body-side mount unit 201 of the camera body 2 by the lens-side mount unit 301. Note that the camera 1 may be a camera in which the camera body 2 and the lens unit 3 are integrally configured (a fixed-lens camera).

[0008] When the interchangeable lens 3 is attached to the camera body 2, a terminal provided on the body side connection part 202 is electrically connected to a terminal provided on the lens side connection part 302. This enables power to be supplied from the camera body 2 to the interchangeable lens 3 and communication between the camera body 2 and the interchangeable lens 3.

[0009] The interchangeable lens 3 includes a photographing optical system (imaging optical system) 31, a lens control unit 32, and a lens memory 33. The interchangeable lens 3 is, for example, a zoom lens. The photographing optical system 31 includes multiple lenses, including a lens (variable magnification lens) 31a that changes the focal length and a focus lens (focus adjustment lens) 31b, and an aperture 31c, and forms a subject image on the imaging surface of the image sensor 21.

[0010] The lens control unit 32 is configured with a processor such as a CPU, FPGA, or ASIC, and memories such as ROM and RAM, and controls each unit of the interchangeable lens 3 based on a control program. The lens control unit 32 controls the driving of the lens 31a, focus lens 31b, and aperture 31c based on signals input from the body control unit 22 of the camera body 2 via the body side connector 202 and the lens side connector 302.

[0011] For example, when a signal indicating the movement direction, amount of movement, movement speed, etc. of the focus lens 31b is input from the body control unit 22 to the lens control unit 32, the lens control unit 32 moves the focus lens 31b forward or backward in the direction of the optical axis L based on the signal, thereby changing the imaging position of the subject image formed by the photographic optical system 31. Furthermore, the lens control unit 32 controls the position of the lens 31a and the aperture diameter of the diaphragm 31c based on a signal output from the body control unit 22 of the camera body 2.

[0012] The lens memory 33 is configured, for example, by a non-volatile storage medium or the like. The lens memory 33 stores information related to the interchangeable lens 3. In this embodiment, the lens memory 33 stores information related to the coefficients of a function that represents the chromatic aberration of magnification of the photographic 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 control unit 32. The chromatic aberration of magnification information may be stored in a memory internal to the lens control unit 32, or may be stored in the body memory 23 (or a memory internal to the body control unit 22) described below.

[0013] After the interchangeable lens 3 is attached to the camera body 2, the lens control unit 32 transmits information about the chromatic aberration of magnification to the body control unit 22 via the lens-side connector 302 and the body-side connector 202. That is, the lens control unit 32 functions as a transmitter that transmits information about the chromatic aberration of magnification of the photographic optical system 31 to the camera body 2, and the body control unit 22 functions as a receiver that receives information about the chromatic aberration of magnification of the photographic optical system 31 from the interchangeable lens 3. The lens control unit 32 also transmits to the body control unit 22 position information (focal length information) of the controlled lens 31a, position information of the controlled focus lens 31b, and information about the aperture value (F-number) of the controlled aperture 31c.

[0014] Next, we will explain the configuration of the camera body 2. The camera body 2 includes an image sensor 21, a body control unit 22, a body memory 23, a display unit 24, and an operation unit 25.

[0015] The imaging element 21 is, for example, a CMOS image sensor or a CCD image sensor. The imaging element 21 receives a light beam that has passed through the photographing optical system 31 and captures an image of a subject. The imaging element 21 has a plurality of pixels, each having a photoelectric conversion unit, arranged two-dimensionally (for example, in the row and column directions). The photoelectric conversion unit is formed, for example, by a photodiode (PD). The imaging element 21 photoelectrically converts the received light to generate a signal. The signal generated by the imaging element 21 is output from the imaging element 21 to the body control unit 22 as image data (image signal).

[0016] The body memory 23 is composed of, for example, a non-volatile storage medium. 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 images based on the image data, shooting-related information such as shutter speed and aperture value, and menu screens, etc. The operation unit 25 includes various setting switches such as a release button, a power switch, and switches for switching between various modes, and outputs operation signals to the body control unit 22 in response to each operation.

[0017] The body control unit 22 is configured with a processor such as a CPU or FPGA, and memories such as ROM or RAM, and controls each unit of the camera 1 based on a control program. The body control unit 22 generates signals that control the drive of the lens 31a, focus lens 31b, and aperture 31c, and outputs the generated signals to the lens control unit 32. The body control unit 22 also performs image processing on image data output from the image sensor 21. Image processing includes well-known image processing such as tone conversion processing, color interpolation processing, and edge enhancement processing.

[0018] The body control unit 22 according to this embodiment uses the above-described chromatic aberration of magnification information to perform correction processing on the image data output from the image sensor 21, and generates image data in which color shift due to chromatic aberration of magnification has been reduced. The chromatic aberration of magnification information used when correcting color shift due to chromatic aberration of magnification will be described below.

[0019] Even when light comes from the same subject, light of different wavelengths (bands), such as R (red), G (green), and B (blue), forms images at different positions on the image sensor 21 due to chromatic aberration of magnification. Because light from the subject forms images at different image heights depending on its wavelength, the subject images formed by light of each wavelength of R, G, and B have different image sizes, i.e., different image magnifications. For this reason, the image data obtained by capturing a subject image using the imaging optical system 31 is affected by chromatic aberration of magnification caused by the imaging optical system 31, resulting in color shifts.

[0020] Fig. 2 is a diagram showing an example of the amount of color shift caused by lateral chromatic aberration. In Fig. 2, the horizontal axis represents image height (unit: mm, for example), and the vertical axis represents the amount of shift from a reference color component (unit: mm, for example). In the example shown in Fig. 2, of the color components (R, G, and B components) of the image data, the G component is used as the reference, and waveform 41 represents the amount of shift between the G component and the R component, while waveform 42 represents the amount of shift 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.

[0021] The lateral chromatic aberration of the imaging optical system 31 can be expressed by a function equation 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 lateral chromatic aberration is expressed by a function LCR(r) in which the image height ratio r (= image height / maximum image height), which is the ratio of the image height to the maximum image height, is a variable. Here, the maximum image height represents the maximum image height on the imaging surface of the image sensor 21. Furthermore, the image height ratio corresponding to the position of the signal to be corrected in the image data is defined as r0, and the image height ratio corresponding to the position of the signal to be corrected after correction is defined as r1. The image height ratio r0 represents the pixel position on the image sensor 21 before correction, and the image height ratio r1 represents the pixel position on 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)

[0022] For example, if the positions of the R and B components of the image data (R, G, and B components) are corrected using the G component as a reference, the image height ratio r0 in equation (1) indicates the image height before correction, i.e., the image height corresponding to the position of the R or B component signal on the sensor (image sensor 21) where the image was captured, and the image height ratio r1 indicates the image height corresponding to the position of the R or B component signal after lateral chromatic aberration has been corrected. LCR(r) is a function of the ratio between the positions of the images of different color components, for example, the ratio between the position of the G component and the position of the R or B component, and can also be thought of as representing the amount of magnification change required to correct for color shift. The function LCR(r) varies depending on the amount of color shift due to lateral chromatic aberration, and will take different values ​​for different lens types even with the same focal length and shooting distance.

[0023] A function LCR(r) representing the lateral chromatic aberration can be expressed, for example, by the following equation (2). LCR(r)=a+br 2 +cr 3 …(2) In this equation (2), coefficient a is the coefficient of the zeroth-order term of the image height ratio r, coefficient b is the coefficient of the second-order term of the image height ratio r, and coefficient c is the coefficient of the third-order term of the image height ratio r. In function equation (2) with image height ratio r as a variable, a is a constant term. The function LCR(r) changes according to the image height ratio r, as shown in FIG. 3, for example. The coefficients a, b, and c each change according to the lens arrangement in the photographic optical system 31. In other words, the amount of color shift due to lateral chromatic aberration differs not only depending on the wavelength of light and image height, but also on the lens position (focal length and shooting distance) of the lens used for photographing. In the case of a zoom lens, the amount of color shift changes depending on both the focal length and shooting distance, while in the case of a prime lens, the amount of color shift changes depending on the shooting distance.

[0024] The coefficients a, b, and c change when the focal length or shooting distance is changed, but they can be determined in advance by performing simulations using design data for the lens used for shooting or experiments using an actual lens. As a result of simulations, the inventors discovered that by performing correction using the above-mentioned equations (1) and (2), color shift caused by lateral chromatic aberration can be accurately corrected using an approximate equation with a small number of terms, namely, the zeroth-order term, the second-order term, and the third-order term of the image height ratio r. Below, as an example, a case will be described in which the focal length f and the shooting distance d are each changed in five ways, and 25 different coefficients a, b, and c are obtained through simulations using design data.

[0025] Fig. 4 is a table showing coefficients of a function representing lateral chromatic aberration in 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 shooting 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 out of the coefficients a (a11 to a55), coefficients b (b11 to b55), and coefficients c (c11 to c55).

[0026] 5, for example, by referring to the coefficients a11, a12, a13, a14, and a15 when the shooting distance is d1, it is possible to grasp how the coefficient a changes with the focal length f when the shooting distance is d1. Therefore, by performing calculations using these coefficients a11, a12, a13, a14, and a15, it is possible to approximate the coefficient a, which changes according to the focal length f when the shooting distance is d1, with a curve. For example, the function a(f), which represents the coefficient a that changes depending on the focal length f, is expressed by the following equation (3).

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[0027] Furthermore, for example, by referencing the coefficients a11, a21, a31, a41, and a51 when the focal length is f1, it is possible to grasp how the coefficient a changes when the shooting distance d is changed when the focal length is f1. Therefore, by performing calculations using these coefficients a11, a21, a31, a41, and a51, it is possible to approximate the coefficient a, which changes depending on the shooting distance d when the focal length is f1, with a curve. For example, the function a(d), which represents the coefficient a that changes depending on the shooting distance d, is expressed by the following equation (4).

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[0028] Furthermore, by expanding the above-mentioned method, the coefficient a, which changes depending on the focal length and shooting distance, can be approximated by a curved surface by performing calculations using 25 pieces of data for the coefficient a (coefficients a11 to a55) shown in Fig. 5. For example, the function a(f, d) representing the coefficient a, which changes depending on the focal length f and shooting distance d, is expressed by the following equation (5).

number

[0029] This equation (5) consists of 12 terms obtained by combining the above equations (3) and (4). By using equation (5), the coefficient a can be approximated by a curved surface, as shown in the example in Figure 6. In other words, equation (5) is an approximation model for estimating the coefficient a. The 12 coefficients (A 00 ~A 32 ) is calculated based on the 25 coefficients a11 to a55 shown in FIG. 5. Specifically, the coefficients (A 00 ~A 32 ) by fitting the 12 coefficients A in Eq. (5) 00 ~A 32 The value of is selected.

[0030] Similarly, a function b(f) representing a coefficient b that changes depending on the focal length f is expressed by the following equation (6) by performing a calculation using coefficients b11 to b15 shown in FIG.

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[0031] Furthermore, a function b(d) representing a coefficient b that changes depending on the shooting distance d is expressed by the following equation (7) by performing a calculation using coefficients b11 to b51, for example.

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[0032] Furthermore, by performing calculations using 25 pieces of data for coefficient b (coefficients b11 to b55), a function b(f, d) representing coefficient b that changes depending on focal length f and shooting distance d is expressed by the following equation (8).

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[0033] Furthermore, a function c(f) representing a coefficient c that changes depending on the focal length f is expressed by the following equation (9) by performing a calculation using coefficients c11 to c15 shown in FIG.

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[0034] A function c(d) representing a coefficient c that changes depending on the shooting distance d is expressed by the following equation (10) by performing a calculation using coefficients c11 to c51, for example.

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[0035] Furthermore, by performing calculations using 25 pieces of data for the coefficient c (coefficients c11 to c55), the function c(f, d) representing the coefficient c that changes depending on the focal length f and the shooting distance d is expressed by the following equation (11).

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[0036] As mentioned above, the 12 coefficients A that approximate the coefficient a 00 ~A 32 , 12 coefficients B that approximate coefficient b 00 ~B 32 , and 12 coefficients C that approximate the coefficient c 00 ~C 32A total of 36 coefficients (approximation coefficients) are calculated. Information about these approximation coefficients is stored in the lens memory 33 of the interchangeable lens 3 as the above-mentioned chromatic aberration of magnification information. That is, the lens memory 33 stores chromatic aberration of magnification information related to the coefficients a, b, and c of the function formula (2) that represents the chromatic aberration of magnification of the photographic optical system 31.

[0037] Furthermore, the amount of color shift is not only due to lateral chromatic aberration, but also depends on the aperture value of the aperture 31c, since it is affected by spherical aberration and other chromatic aberrations. 00 ~A 32 , B 00 ~B 32 , C 00 ~C 32 ) is calculated for a plurality of aperture values ​​and stored in the lens memory 33. For example, information on 36 approximation coefficients for the first aperture value and information on 36 approximation coefficients for the second aperture value are stored in the lens memory 33. Note that the 36 approximation coefficients may be calculated for the number of aperture stops and stored in the lens memory 33 in advance.

[0038] Furthermore, in this embodiment, in order to correct the color shift between the G component and the R component and the color shift between the G component and the B component, information on approximation coefficients for estimating the amount of color shift between the G component and the R component and information on approximation coefficients for estimating the amount of color shift between the G component and the B component are stored in the lens memory 33.

[0039] 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 any timing, for example, during initial communication after the interchangeable lens 3 is attached to the camera body 2. The information of the above-mentioned formulas (1) and (2) is also stored in the internal memory of the body control unit 22.

[0040] The body control unit 22 calculates LCR(r) based on the above-mentioned formula (2), the lateral chromatic aberration information transmitted from the interchangeable lens 3, and the lens position information at the time of shooting. The body control unit 22 also calculates the amount of color shift due to lateral chromatic aberration using the above-mentioned 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 to correct the image data so that it becomes image data for each pixel when an image is captured using an imaging optical system 31 that does not have lateral chromatic aberration. For example, the body control unit 22 performs a process to convert the coordinates of the image data based on the calculated amount of color shift. More specifically, the body control unit 22 performs a correction process to shift the R component signal so that the amount of shift between the G component and the R component is reduced, and to shift the B component signal so that the amount of shift between the G component and the B component is reduced. This allows the body control unit 22 to generate image data with reduced color shift due to lateral chromatic aberration.

[0041] 7 is a flowchart showing an example of the operation of the camera 1 according to this embodiment. The example of the operation of the camera 1 will be described with reference to the flowchart of FIG.

[0042] In step S100, for example after the power is turned on, the body control unit 22 of the camera body 2 transmits a signal requesting transmission of chromatic aberration of magnification information to the interchangeable lens 3. In step S200, the lens control unit 32 of the interchangeable lens 3 receives the request signal for chromatic aberration of magnification information from the camera body 2.

[0043] In step S210, the lens control unit 32 transmits the chromatic aberration of magnification 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 transmits the approximation coefficients (coefficient A 00 ~A 32 , B 00 ~B 32 , C 00 ~C 32) to the camera body 2. In step S110, the body control unit 22 receives the approximation coefficient information from the interchangeable lens 3 and stores it in an internal memory or the like of the body control unit 22.

[0044] In step S120, when a release operation is performed using the operation unit 25, the body control unit 22 causes the image sensor 21 to capture an image of a subject and output image data. Also, in step S220, the lens control unit 32 transmits information (status information) about the state of the photographic optical system 31 at the time of release to the camera body 2. This status information includes, for example, focal length information, shooting distance information, and aperture value information. Specifically, the lens control unit 32 transmits the above-mentioned normalized values ​​(fr / f), (dr / d), and aperture stop number as focal length and shooting distance information to the camera body 2. This status information may be transmitted to the camera body 2 periodically, or repeatedly whenever these values ​​change.

[0045] In step S130, the body control unit 22 references the approximation coefficients for the aperture value at the time of image capture based on the transmitted status information and approximation coefficient information, and determines function a(f,d) in equation (5) above, function b(f,d) in equation (8), and function c(f,d) in equation (11) above. The body control unit 22 also calculates coefficients a, b, and c by substituting the focal length f and shooting distance d at the time of image capture into equations (5), (8), and (11). The calculated coefficients a, b, and c are then substituted into equation (2) above to determine function LCR(r).

[0046] In step S140, based on the function LCR(r) and the image height ratio r, the body control unit 22 performs the above-described color shift correction process on the image data output from the image sensor 21. In this way, the body control unit 22 according to the present embodiment generates image data in which color shift due to lateral chromatic aberration has been reduced.

[0047] According to the above-described embodiment, the following effects can be obtained. (1) The interchangeable lens 3 is an interchangeable lens 3 that can be attached to the camera body 2, and includes a storage unit (e.g., lens memory 33) that stores information (approximation coefficient information) about the coefficients of a function LCR(r) that represents the chromatic aberration of magnification of the optical system 31, approximated using at least one of the shooting distance and the focal length, and a transmission unit (lens control unit 32) that transmits the information about the coefficients stored in the storage unit to the camera body 2. By referencing the approximation coefficient information transmitted from the interchangeable lens 3, the camera body 2 can grasp the amount of color shift due to chromatic aberration of magnification at all non-discrete lens positions and generate image data in which color shift due to chromatic aberration of magnification is reduced. As a result, degradation of image quality can be suppressed.

[0048] (2) The function LCR(r) has as its variable the image height ratio r, which is the ratio of the image height to the maximum image height. In this embodiment, the amount of color shift due to lateral chromatic aberration is expressed using a function LCA(r) of the image height ratio r. Therefore, the amount of color shift can be expressed using information that is independent of the pixel pitch (pixel spacing), which is information specific to the image sensor 21, and the use of this LCA(r) enables efficient correction processing.

[0049] (3) The function LCR(r) expresses the ratio of the positions of images of different color components using a third-order term of the image height ratio r, a second-order term of the image height ratio r, and a constant term. The storage unit stores the coefficient of the third-order term, the coefficient of the second-order term, and the constant of the constant term as information related to the coefficients. In this embodiment, the function LCR(r) is made up of a third-order term, a second-order term, and a zeroth-order term of the image height ratio r. This makes it possible to express the amount of color shift due to chromatic aberration of magnification with a small number of terms with high accuracy. In addition, the lens memory 33 stores approximation coefficients (coefficient A) that approximate the coefficients a, b, and c of these three terms. 00 ~A 32 , B 00 ~B 32 , C 00 ~C 32 ) is stored. This makes it possible to reduce the amount of data stored in the lens memory 33. Also, it is possible to reduce the amount of calculation required to perform color shift correction processing.

[0050] (4) The coefficients a, b, and c of the function LCR(r) are approximated by a function with variables being the ratio (fr / f) of the minimum focal length fr to the focal length f and the ratio (dr / d) of the minimum shooting distance dr to the shooting distance d. In this embodiment, when the interchangeable lens 3 notifies the camera body 2 of focal length and shooting distance information, it transmits normalized values ​​(fr / f) and (dr / d) to the camera body 2. This makes it possible to notify the camera body 2 of the lens position required for correction (focal length information and shooting distance information) using data with a fixed bit length 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.

[0051] The following modifications are also within the scope of the present invention, and one or more of the modifications may be combined with the above-described embodiment.

[0052] (Variation 1) In the above-described embodiment, an example has been described in which the function LCR(r) is expressed by three terms. However, it may be expressed by one term consisting of only the zeroth-order component, by two terms, or by four or more terms. Furthermore, for example, LCR(r) may be expressed by three terms, namely, a second-order term, a first-order term, and a zeroth-order term of the image height ratio r.

[0053] (Variation 2) In the above-described embodiment, an example has been described in which the coefficients a, b, and c of the function LCR(r) are approximated by functions that use the focal length and shooting distance as variables. However, the coefficients a, b, and c may also be approximated by functions that use only one of the focal length and shooting distance as a variable. For example, if the interchangeable lens 3 is a fixed-focus lens, the coefficients a, b, and c may be expressed by functions that use the shooting distance as a variable.

[0054] (Variation 3) In the above-described embodiment, an example has been described in which the coefficients a, b, and c of the function LCR(r) are approximated by functions whose variables are the ratio (fr / f) of the minimum focal length fr to the focal length f and the ratio (dr / d) of the minimum shooting distance dr to the shooting distance d. However, the coefficients a, b, and c may also be approximated by functions whose variables are the reciprocal of the focal length f or the reciprocal of the shooting distance d.

[0055] (Variation 4) In the embodiment described above, the lens control unit 32 of the interchangeable lens 3 transmits normalized values ​​(fr / f) and (dr / d) as information on the focal length and shooting distance, respectively, to the camera body 2. Instead of (fr / f), the lens control unit 32 transmits information on the integer (f info ) may be transmitted to the camera body 2. Alternatively, the lens control unit 32 may transmit, instead of (dr / d), integer information (d info ) may be transmitted to the camera body 2. In this case, (fr / f) and (dr / d) can be limited to n-bit fixed-length information, while the amount of information can be made appropriate for aberration correction. info ) and (d info ) may have different bit depths. f info ≡int{2 n ×(fr / f)} …(12) d info ≡int{2 n ×(dr / d)} …(13)

[0056] (Variation 5) 7, in step S210, the interchangeable lens 3 transmits all of the information on the approximation coefficients acquired for multiple aperture values ​​to the camera body 2. However, instead of this, the interchangeable lens 3 may transmit to the camera body 2 only the approximation coefficients associated with the aperture value at the time of shooting.

[0057] (Variation 6) 7, in step S210, the interchangeable lens 3 transmits all of the approximation coefficient information to the camera body 2. However, instead of this, the interchangeable lens 3 may use the approximation coefficients, lens positions f and d, and aperture stops to calculate magnification aberration correction coefficients a, b, and c at the time of shooting, and transmit the correction coefficients a, b, and c to the camera body 2.

[0058] (Variation 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, a decrease in the signal value (pixel value) of an image signal (image data) caused by a decrease in the amount of light at the periphery compared to the center of the optical axis is corrected. The function Vig(r) representing the value (peripheral illumination correction amount) used when correcting the decrease in pixel value due to a decrease in the amount of light (light reduction) can be expressed, for example, by the following equation (14): Vig(r)=ar 2 +br 4 +cr 6 …(14) Vig(r) is a function related to the ratio of the amount of light at the center of the optical axis to the amount of light at a position with an image height ratio r, and represents the amount of correction used to correct for a decrease in pixel value due to peripheral vignetting. In this equation (14), coefficient a is the coefficient of the second-order term of the image height ratio r, coefficient b is the coefficient of the fourth-order term of the image height ratio r, and coefficient c is the coefficient of the sixth-order term of the image height ratio r. The coefficients a, b, and c each vary depending on the focal length, shooting distance, and aperture stop number of the photographic optical system 31.

[0059] Similar to the case of the above-described embodiment, a plurality of coefficients (approximation coefficients) that respectively approximate the coefficients a, b, and c are calculated. Information on these approximation coefficients is stored in the lens memory 33 of the interchangeable lens 3 (or in the memory inside the lens control unit 32). That is, information on the coefficients a, b, and c of the function formula (14) that expresses the amount of peripheral illumination correction for the photographic optical system 31 is stored in the lens memory 33 (or in the memory inside the lens control unit 32).

[0060] The body control unit 22 calculates Vig(r) based on the above-mentioned equation (14), the information on 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. By multiplying the signal to be corrected by the calculated Vig(r), the body control unit 22 can correct the image data to achieve uniform brightness. This makes it possible to obtain image data in which the decrease in pixel value due to a decrease in the amount of light is reduced.

[0061] (Variation 8) The imaging devices described in the above embodiments and variations may be applied to cameras, smartphones, tablets, cameras built into PCs, in-vehicle cameras, cameras mounted on unmanned aerial vehicles (drones, radio-controlled aircraft, etc.), etc.

[0062] (Variation 9) In the above-described embodiment and modified examples, image data is corrected by the imaging device. However, image data may also be corrected by an external device (such as a computer, a tablet device, or another camera). Image data correction processing may also be performed in a camera system consisting of an imaging device and an external device. The imaging device (e.g., camera 1) stores information on coefficients a, b, and c at the time of shooting along with the image data. After shooting, the external device (e.g., a computer) performs the correction processing described above using the image data and information on coefficients a, b, and c acquired from the imaging device. This allows the camera system to generate image data in which color shift due to lateral chromatic aberration and pixel value reduction due to reduced light intensity are reduced. Data communication between the imaging device and the external device may be performed using a storage medium such as a memory card, or via wireless or wired communication. An image processing device may also be configured by having a computer (processor) execute a program that performs processing based on the flowchart illustrated in FIG. 7. The program may be provided as a computer program product in various forms, such as via a storage medium or a communication line.

[0063] Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments that are conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0064] 1...imaging device, 2...camera body, 3...interchangeable lens, 21...imaging element, 22...body control unit, 31...photographic optical system, 32...lens control unit, 33...lens memory

Claims

1. An interchangeable lens that can be attached to a camera body, a storage unit that stores coefficient information relating to coefficients of a first function that represents the chromatic aberration of magnification of the optical system; a transmitter that transmits the coefficient information and status information relating to at least one of the photographing distance and the focal length of the optical system to the camera body; Equipped with The coefficient information includes at least one of first information on coefficients approximated by a second function having a ratio of a minimum shooting distance to the shooting distance as a variable, or second information on coefficients approximated by a third function having a ratio of a minimum focal length to the focal length as a variable.

2. The interchangeable lens according to claim 1 , wherein the transmission unit transmits the status information to the camera body when an operation related to photography is performed on the camera body side.

3. 3. The interchangeable lens according to claim 1, wherein the transmitter transmits the status information to the camera body after transmitting at least one of the first information and the second information to the camera body.

4. The interchangeable lens according to claim 1 , wherein the state information is a normalized value.

5. The interchangeable lens according to claim 1 , wherein the first function has information relating to a distance from an optical axis on an image plane as a variable.

6. The interchangeable lens according to claim 1 , wherein the first function has an image height ratio, which is a ratio of an image height to a maximum image height, as a variable.

7. 7. The interchangeable lens according to claim 6, wherein the first function represents a ratio between positions of images of different color components using at least one of a third-order term of the image height ratio, a second-order term of the image height ratio, and a constant term.

8. The interchangeable lens according to claim 7 , wherein the storage section stores, as the coefficient information, at least one of a coefficient of the third-order term, a coefficient of the second-order term, and a constant of the constant term.

9. the storage unit stores both the first information and the second information; The interchangeable lens according to claim 1 , wherein the transmitter transmits both the first information and the second information to the camera body.

10. The interchangeable lens according to claim 1 , wherein the first information includes a coefficient of the second function, which is a ratio of the minimum shooting distance to the shooting distance.

11. The interchangeable lens according to claim 1 , wherein the second information includes a coefficient of a ratio of the minimum focal length to the focal length of the third function.

12. the optical system has a diaphragm; 12. The interchangeable lens according to claim 1, wherein the storage unit stores at least one of the first information or the second information in the case of a first aperture value, and at least one of the first information or the second information in the case of a second aperture value.

Images