Lens device, imaging apparatus, and control method of lens device

Abstract

[Problem] To enable a change of view angle to be corrected even for an image processor not having a function for correcting a change of view angle due to focusing. [Solution] A lens device 100 includes: storage means 14, 15 for storing correction information used in a first correction process performed by an image processing device 200 on an image generated by image capturing through an imaging optical system 11; and a control means 18 for transmitting the correction information to the image processing device. The imaging optical system has a configuration that gives rise to distortion aberration and a change of view angle due to focusing. The correction information includes first correction information used for correcting the distortion aberration by the first correction processing, and second correction information used for correcting the change of view angle together with the distortion aberration by the first correction processing. The control means transmits at least one of the first correction information and the second correction information to the image processing device.

Description

Lens device, imaging device, and control method of lens device

[0007] ,

[0006] ,

[0001] The present invention relates to a lens device used for imaging.

[0002] In some imaging optical systems, when the focus lens is moved, an angle-of-view fluctuation (focus breathing) occurs. Patent Document 1 discloses an imaging device that corrects focus breathing by converting the size of an image based on the imaging magnification for each position of the focus lens.

[0003] Japanese Patent Application Laid-Open No. 2007-142965

[0004] However, some imaging devices do not have a function of correcting focus breathing. It is desirable that such an imaging device can also correct focus breathing.

[0005] A lens device according to one aspect of the present invention includes an imaging optical system, a storage unit that stores correction information used for a first correction process performed by an image processing device (imaging device) on an image generated by imaging through the imaging optical system, and a control unit that transmits the correction information to the image processing device. The imaging optical system has a configuration that causes distortion aberration and an angle-of-view fluctuation due to focusing. The correction information includes first correction information used for correcting distortion aberration by the first correction process and second correction information used for correcting the angle-of-view fluctuation together with the distortion aberration by the first correction process. The control unit is characterized by transmitting at least one of the first correction information and the second correction information to the image processing device. Note that an image processing device that receives at least one of the first correction information and the second correction information from the lens device as correction information and performs the first correction process on an image using the correction information also constitutes another aspect of the present invention.

[0006] According to the present invention, even an imaging device that does not have a function of correcting the angle-of-view fluctuation can correct the angle-of-view fluctuation together with the distortion aberration using the second correction information.

[0007] A block diagram showing the configuration of the lens device and camera in the embodiment. A diagram showing the first correction information in the embodiment. A diagram showing the second correction information in the embodiment. A diagram showing the third correction information in the embodiment. A flowchart showing the processing in Embodiment 1. A flowchart showing the processing in Embodiment 2. A flowchart showing the processing in Embodiment 2. A diagram showing an example of distortion aberration and its correction result.

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0009] Figure 1 shows the configuration of a camera system as an embodiment. The camera system has a lens device 100 and an imaging device (hereinafter referred to as camera) 200 as an image processing device. The camera 200 is a digital video camera, a digital still camera, a broadcast camera, a surveillance camera, etc. The lens device 100 is attached to the camera 200 in a way that allows for attachment and communication.

[0010] The lens device 100 includes an imaging optical system 11, a focus position sensor 13, a first correction information storage unit 14, a second correction information storage unit 15, and a third correction information storage unit 16 as storage means, a lens CPU 18 as a control means, and a communication unit 17. The imaging optical system 11 includes a focus lens group 12. By moving the focus lens group 12 in the optical axis direction of the imaging optical system 11, a state of focus can be obtained in the focus range from a nearby object to an object at infinity. The focus lens group 12 may be one group or multiple groups, such as in a floating focus system. The imaging optical system 11 has an optical configuration that produces distortion aberration and focus breathing as a change in the angle of view due to the movement (focusing) of the focus lens group 12. The focus position sensor 13 detects the position of the focus lens group 12 in the optical axis direction.

[0011] The first correction information storage unit 14 stores (prepares) first correction information. The first correction information is used in the first correction process to correct distortion aberration in the image generated by imaging in the camera 200, and consists of multiple correction values ​​that differ for each image height. The second correction information storage unit 15 stores second correction information. The second correction information is used in the first correction process to correct distortion aberration in the image generated by imaging and to simultaneously correct (suppress) focus breathing, and consists of multiple correction values ​​that differ for each image height. Details of the first and second correction information will be described later.

[0012] The third correction information storage unit 16 stores the third correction information. The third correction information is used in the breathing correction process (second correction process), which corrects focus breathing by enlarging the image generated by imaging and converting the image size, separate from the distortion aberration correction (first correction process), and is information indicating the magnification ratio of the image. The function of performing the breathing correction process as the second correction process in the camera 200 is called the breathing correction function.

[0013] The first to third correction information storage units 14 to 16 may store the first to third correction information in advance when the lens device 200 is shipped from the factory, or they may temporarily store the first to third correction information downloaded via communication from a server on the cloud each time it is used for imaging.

[0014] The lens CPU 18 is a computer that controls the driving of the zoom lens group (not shown), aperture unit, and focus lens group 12 included in the imaging optical system 11. The lens CPU 18 can also transmit first correction information, second correction information, and third correction information to the camera 200 via the communication unit 17.

[0015] The camera 200 has an image sensor 21 and a camera CPU 22. The image sensor 21 is a photoelectric conversion element such as a CCD sensor or CMOS sensor that photoelectrically converts (images) the optical image formed by the imaging optical system 11. The camera CPU 22 is a computer and includes an image processing unit 23 and an ID storage unit 24.

[0016] When the camera 200 is attached to the lens device 100, it transmits camera identification information (hereinafter referred to as camera ID) read from the ID storage unit 24 to the lens CPU 18 via the communication unit 17 of the lens device 100. The camera ID is information used to identify the model and individual camera 200, such as the model name and serial number of the camera 200.

[0017] The image processing unit 23 performs image processing on the imaging signal from the image sensor 21 to generate an image. The image processing unit 23 also performs the first correction process described above on the generated image (image to be corrected). Among the multiple cameras to which the lens 100 can be attached, there are models in which the image processing unit 23 has the breathing correction function described above and models in which it does not have the breathing correction function.

[0018] Furthermore, the image processing unit 23 determines the shape of the distortion from the image. If the shape of the distortion is pincushion-shaped, the magnification indicated by the third correction information may be changed to a magnification appropriate for correcting pincushion-shaped distortion. This makes it possible to correct pincushion-shaped distortion effectively.

[0019] The image processing unit 23 may be provided in the lens device 100, or it may be configured as an image processing unit separate from the camera system.

[0020] The lens CPU 18 may decide which of the first, second, or third correction information to send to the camera 200 based on the camera ID, that is, depending on whether the camera 200 has a breathing correction function determined from the camera ID. Specifically, if the lens CPU 18 determines from the camera ID that the camera 200 has a breathing correction function, it sends the first and third correction information to the camera 200. If the lens CPU 18 determines from the camera ID that the camera 200 does not have a breathing correction function, it sends the second correction information to the camera 200. The breathing correction function is a function that suppresses (corrects) focus breathing by performing a process to convert the size of the image to be corrected with a magnification ratio (third correction information) that is independent of the image height.

[0021] The lens CPU 18 may also transmit all of the first correction information, second correction information, and third correction information to the camera 200, regardless of the camera ID. In this case, the camera 200 will decide which of the first, second, and third correction information to use, depending on whether or not it has its own breathing correction function and whether or not the breathing correction function selected by the user is enabled or disabled.

[0022] Furthermore, the lens CPU 18 may transmit to the camera 200 any correction information from the first correction information, second correction information, and third correction information that it has received a transmission request for from the camera 200. For example, if the camera 200 has a breathing correction function (or if the breathing correction function is enabled), it will request the lens CPU 18 to transmit the first correction information and the third correction information, and the lens CPU 18 will respond by transmitting the first correction information and the third correction information to the camera 200. If the camera 200 does not have a breathing correction function (or if the breathing correction function is disabled), it will request the lens CPU 18 to transmit the second correction information, and the lens CPU 18 will respond by transmitting the second correction information to the camera 200.

[0023] Figure 2 shows an example of first correction information when the imaging optical system is in a zoom state and focused on a certain subject distance. The vertical axis represents the image height, and the horizontal axis represents the correction values ​​that constitute the first correction information. The solid line 26 represents the correction value for correcting negative distortion (barrel distortion), and the dashed line 27 represents the correction value for correcting positive distortion (pincushion distortion). The image processing unit 23 uses this first correction information to perform a first correction process to reduce distortion.

[0024] Figure 3 shows an example of second correction information when the imaging optical system is in the same state as in Figure 2. The vertical axis represents image height, and the horizontal axis represents the correction values ​​that constitute the second correction information. The solid line 31 represents the correction value for correcting barrel distortion, and the dashed line 27 represents the correction value for correcting pincushion distortion. The second correction information corresponds to each correction value of the first correction information shown in Figure 2 being offset by the breathing correction component C necessary for correcting focus breathing. Component C is a constant value regardless of image height. The image processing unit 23 uses this second correction information to perform the first correction processing to simultaneously reduce distortion and focus breathing.

[0025] Figure 4 shows an example of third correction information when the imaging optical system is in a zoom state. The vertical axis represents the magnification, and the horizontal axis represents the position (focus position) of the focus lens group 12. The magnification increases from 1 as the focus position moves from infinity to near. The image processing unit 23 of the camera 200, which has a breathing correction function, uses this third correction information to perform a second correction process to reduce focus breathing.

[0026] The first correction information and the second correction information are preferably expressed by the following formulas. The first correction information (correction value) f1 is preferably expressed by the following formula (1), where Y is the image height and Y' is the ideal image height, which is the ideal image height obtained by the paraxial magnification.

[0027] f1 = (Y' - Y) / Y (1) Here, the ideal image height Y' is expressed by the following equation (1-1) when the focal length of the imaging optical system is f and the half-angle of view is θ, for example, in the case of a general lens using the central projection method.

[0028] Y' = f × tanθ (1-1) In addition, in the case of other projection methods (conformal projection, uniform solid angle projection, etc.), the ideal height Y' can also be expressed by an equation relating to the ideal height Y' that corresponds to each projection method (for example, in the case of conformal projection, Y' = f × θ).

[0029] By using a correction value expressed as shown in equation (1), it becomes easier to correct the distortion aberration of the imaging optical system in the image.

[0030] Furthermore, the second correction information (correction value) f2 is preferably expressed by the following equations (2-1) and (2-2), where the constant term (breathing correction component) is C.

[0031] When 0 < Y, f2 = {(Y' - Y) / Y} + C (2-1) When Y = 0, f2 = 0 (2-2) Here, equation (2-1) shows the correction value when the image height Y is not at the image center, and equation (2-2) shows the correction value when the image height Y is at the image center. By using the correction values ​​expressed as in equations (2-1) and (2-2), distortion aberration and focus breathing can be corrected at the same time.

[0032] Furthermore, the first and second correction information can be stored in each memory unit in various formats. For example, it may be stored in the form of polynomial coefficients, or in the form of a constant multiplier. It may also be stored in the form of a percentage, or as discrete correction values ​​corresponding to various zoom states and focus positions. If discrete correction values ​​are used, correction values ​​that are not stored can be calculated by interpolation operations such as linear interpolation.

[0033] Furthermore, the constant term C in the second correction information is preferably the paraxial image magnification of the imaging optical system. When y is the distance from the optical axis of an object point on the object plane, and y' is the distance from the optical axis of an image point on the image plane corresponding to the object point, the paraxial image magnification β is defined by the following equation (3).

[0034] β = y' / y (3) By using the paraxial image magnification β, which corresponds to the zoom state and focus position at the time of imaging of the image to be corrected, as a constant term C, it becomes possible to correct focus breathing more effectively.

[0035] The second correction information preferably includes a correction value that can correct the distortion of out-of-focus subject images. When the imaging mode of the camera 200 is a video mode that requires focus breathing correction (i.e., during video recording), the image to be corrected may contain many out-of-focus subject images. For this reason, it is more effective to correct the distortion of out-of-focus subject images, such as distant landscape images, using the second correction information, regardless of the focus position.

[0036] Furthermore, as shown in Figure 1, it is preferable to provide the lens device 100 with a third correction information storage unit 16 that stores a magnification ratio (third correction information) for performing a magnification process as a second correction process on the image to be corrected after distortion correction processing using the first correction information. This makes it possible to correct focus breathing appropriately for the lens device 100 when the lens device 100 is mounted on a camera 200 that has a breathing correction function.

[0037] Furthermore, it is preferable that the first correction processing using the first correction information is performed when the imaging mode of the camera 200 is in still image mode (i.e., when capturing still images). This ensures that in the camera 200 without a breathing correction function, no magnification processing is performed in still image mode, and a sufficient field of view of the imaging optical system is secured when imaging subjects at infinity. In the camera 200 with a breathing correction function, magnification processing is performed even in still image mode.

[0038] Next, we will explain the processes performed by the lens device 100 and the camera 200, respectively.

[0039] The flowchart in Figure 5 shows the process that the lens CPU 18 executes according to the program in Example 1.

[0040] When the lens device 100 is attached to the camera 200 and the camera system is powered on, in step S51, the lens CPU 18 receives a camera ID from the camera 200.

[0041] Next, in step S52, the lens CPU 18 determines whether the camera 200 has a blooming correction function based on the camera ID. If the camera 200 has the blooming correction function, the process of step S53 is performed. If the camera 200 does not have the blooming correction function, the process of step S54 is performed.

[0042] In step S53, the lens CPU 18 transmits the first correction information and the third correction information to the camera 200. Then, this process ends. As a result, the image processing unit 23 of the camera 200 performs a first correction process using the first correction information on the correction target image to correct the distortion aberration, and further performs a second correction process using the third correction information to correct the focus blooming.

[0043] In step S54, the lens CPU 18 transmits the second correction information to the camera 200. Then, this process ends. As a result, the image processing unit 23 of the camera 200 performs a first correction process using the second correction information on the correction target image to correct the distortion aberration and the focus blooming together.

[0044] According to this embodiment, it is possible to correct the distortion aberration and the focus blooming in the camera 200 that performs the first correction process but does not have the blooming correction function.

[0045] The flowchart of FIG. 6 shows the processes executed by the camera CPU 22 in accordance with the program in the second embodiment.

[0046] When the lens device 100 is attached to the camera 200 and the power of the camera system is turned on, in step S61, the camera CPU 22 starts communication with the lens CPU 18 and receives the first correction information, the second correction information, and the third correction information from the lens CPU 18. Also, the camera CPU 22 transmits the camera ID to the lens CPU 18.

[0047] Next, in step S62, the camera CPU 22 starts imaging in response to a user's imaging instruction. Then, in step S63, the camera CPU 22 causes the image processing unit 23 to generate a correction target image.

[0048] Next, in step S64, the camera CPU 22 determines whether the camera 200 has a blooming correction function (or the blooming correction function is selected as valid by the user). If the camera has the blooming correction function, the process of step S65 is performed. If the camera does not have the blooming correction function (or the blooming correction function is selected as invalid), the process of step S66 is performed.

[0049] In step S65, the camera CPU 22 causes the image processing unit 23 to perform a first correction process (distortion correction process) on the correction target image using the first correction information, and further causes the image processing unit 23 to perform a second correction process (blooming correction process) using the third correction information. Then, the process of step S67 is performed.

[0050] In step S69, the camera CPU 22 causes the image processing unit 23 to perform a first correction process (correction process for distortion and focus blooming) on the correction target image using the second correction information. Then, the process of step S67 is performed.

[0051] In step S67, the camera CPU 22 outputs the corrected image. The output image is recorded on a recording medium (not shown) attached to the camera 200 or displayed on a monitor (not shown) provided in the camera 200. Then, this process ends.

[0052] According to this embodiment, the camera 200 that performs the first correction process but does not have the blooming correction function can correct distortion and focus blooming.

[0053] The flowchart of FIG. 8 shows the processes executed by the camera CPU 22 according to the program in the third embodiment.

[0054] When the lens device 100 is attached to the camera 200 and the power of the camera system is turned on, in step S71, the camera CPU 22 starts communication with the lens CPU 18 and transmits the camera ID to the lens CPU 18.

[0055] Next, in step S72, the camera CPU 22 determines whether the camera 200 has a breathing correction function (or whether the user has selected to enable the breathing correction function). If it has a breathing correction function, it performs the process in step S73; if it does not have a breathing correction function (or whether the user has selected to disable the breathing correction function), it performs the process in step S74.

[0056] In step S73, the camera CPU 22 requests the lens CPU 18 to transmit the first correction information and the third correction information, and receives the first correction information and the third correction information from the lens CPU 18. Then it performs the process in step S75.

[0057] In step S74, the camera CPU 22 requests the lens CPU 18 to transmit the first correction information and the second correction information, and receives the first correction information and the second correction information from the lens CPU 18. Then it performs the process in step S75.

[0058] In step S75, the camera CPU 22 starts imaging in response to the user's imaging instruction. Then, in step S76, the camera CPU 22 instructs the image processing unit 23 to generate the image to be corrected.

[0059] Next, in step S77, the camera CPU 22 determines whether the imaging mode of the camera 200 is video mode or not (still image mode). If it is in video mode, it performs the process in step S78; if it is in still image mode, it performs the process in step S712.

[0060] In step S78, the camera CPU 22 determines again whether the camera 200 has a breathing correction function (or whether the user has selected to enable the breathing correction function). If it has a breathing correction function, it performs the process in step S710; if it does not have a breathing correction function (or if the user has selected to disable the breathing correction function), it performs the process in step S711.

[0061] In step S710, the camera CPU 22 instructs the image processing unit 23 to perform a first correction process (distortion correction process) using the first correction information on the image (video) to be corrected, and then to perform a second correction process (breathing correction process) using the third correction information. Then it performs the process in step S713.

[0062] In step S711, the camera CPU 22 instructs the image processing unit 23 to perform a first correction process (correction of distortion and focus breathing) using the second correction information for the image (video) to be corrected. Then it performs the process in step S713.

[0063] In step S712, the camera CPU 22 instructs the image processing unit 23 to perform a first correction process (distortion correction process) using the first correction information for the image to be corrected (still image). Then it performs the process in step S713.

[0064] In step S713, the camera CPU 22 outputs the image after correction processing. The output image is recorded on a recording medium (not shown) attached to the camera 200 or displayed on a monitor (not shown) provided on the camera 200. Then the process ends.

[0065] According to this embodiment, a camera 200 that performs the first correction process but does not have a breathing correction function can be made to correct video distortion and focus breathing. Furthermore, regardless of whether or not it has a breathing correction function, the camera 200 can be made to correct still image distortion.

[0066] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention.

Claims

1. A lens device comprising: an imaging optical system; a storage means for storing correction information used in a first correction process performed on an image processing device on an image generated by imaging through the imaging optical system; and a control means for transmitting the correction information to the image processing device, wherein the imaging optical system has a configuration that generates distortion and angle of view changes due to focusing; the correction information includes first correction information used to correct the distortion by the first correction process and second correction information used to correct the angle of view changes together with the distortion by the first correction process; and the control means transmits at least one of the first correction information and the second correction information to the image processing device.

2. The lens device according to claim 1, characterized in that the first correction information is used in the first correction process in the image processing device which performs a second correction process to correct the angle of view variation for the image, and the second correction information is used in the first correction process in the image processing device which does not perform the second correction process.

3. The lens device according to claim 2, characterized in that the control means obtains information from the image processing device indicating whether or not the image processing device performs the second correction process, and transmits the first correction information or the second correction information to the image processing device based on said information.

4. The lens device according to claim 3, characterized in that the information is identification information of the image processing device.

5. The lens device according to any one of claims 1 to 4, characterized in that, when the image height is Y and the ideal image height is Y', the first correction information f1 is expressed by the formula f1 = (Y' - Y) / Y.

6. The lens device according to any one of claims 1 to 5, characterized in that, when the image height is Y, the ideal image height is Y', and a constant term independent of the image height is C, the second correction information f2 is expressed by the following equations: When 0 < Y, f2 = {(Y' - Y) / Y} + C When Y = 0, f2 = 0 7. The lens device according to claim 6, characterized in that the constant term C is the paraxial image magnification of the imaging optical system.

8. The lens apparatus according to any one of claims 1 to 7, characterized in that the second correction information is used to correct the distortion aberration of the out-of-focus subject image by the first correction process.

9. The lens device according to any one of claims 1 to 8, wherein the storage means further stores third correction information used in the second correction processing on an image after the first correction processing using the first correction information, and the control means transmits the first correction information and the third correction information to the image processing device that performs the second correction processing.

10. The lens device according to any one of claims 1 to 9, characterized in that the first correction information is used in the first correction processing for a still image as the image in the image processing device that does not perform the second correction processing, and the second correction information is used in the first correction processing for a moving image as the image in the image processing device that does not perform the second correction processing.

11. A lens device comprising: an imaging optical system; a storage means for storing correction information used in a first correction process performed on an image processing device on an image generated by imaging through the imaging optical system; and a control means for transmitting the correction information to the image processing device, wherein the imaging optical system has a configuration that generates distortion aberration and angle of view fluctuation due to focusing, and the correction information is information used in the first correction process to correct the angle of view fluctuation together with the distortion aberration in the image processing device, which does not perform a second correction process to correct the angle of view fluctuation.

12. The lens device according to any one of claims 1 to 11, characterized in that the image processing device is included in an imaging device that detachably mounts the lens device and performs imaging through the imaging optical system.

13. An image processing apparatus characterized by receiving at least one of the first correction information and the second correction information as correction information from a lens device according to any one of claims 1 to 12, and performing the first correction processing on the image using the correction information.

14. An image processing apparatus characterized by receiving the third correction information from the lens device described in claim 9, and, when the distortion is pincushion type, modifying the third correction information according to the shape of the distortion and performing the second correction processing.

15. A control method for a lens device having an imaging optical system, comprising the steps of: preparing correction information to be used in a first correction process performed on an image processing device on an image generated by imaging through the imaging optical system; and transmitting the correction information to the image processing device, wherein the imaging optical system has a configuration that generates distortion and angle of view changes due to focusing; the correction information includes first correction information used to correct the distortion by the first correction process and second correction information used to correct the angle of view changes together with the distortion by the first correction process; and transmitting at least one of the first correction information and the second correction information to the image processing device.

16. A program characterized by causing a computer to execute a process according to the control method described in claim 15.

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