JP2018129648A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device that makes a live view image good for an electronic view finder displayed on a display via an eyepiece optical system at the time of photographing and allows the eyepiece optical system to be made smaller.SOLUTION: An imaging device includes: an imaging element 112; image processing means 120; a display 124 for displaying an image using image data corrected by the image processing means; and an eyepiece optical system 303 provided in order to observe the display 124. The image processing means 120 applies quantity-of-light fall-off correction to the image data generated by the imaging element 112 on the basis of an optical characteristic of an imaging optical system 201 used for forming a subject image on the imaging element when the imaging element generates image data and an optical characteristic of the eyepiece optical system 303, and displays an image on the display 124 using the image data after the quantity-of-light fall-off correction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to image processing for correcting image data generated by an image sensor, and in particular, an electronic viewfinder (EVF) provided with an eyepiece optical system (eyepiece lens) for observing image data. It is related with the imaging device which has.

  In an imaging device that captures an object by obtaining an optical image through a lens, the so-called peripheral light intensity drop phenomenon in which the amount of light decreases as it goes from the center of the captured image to the periphery of the image. Occurs. Further, it is known that the peripheral light amount drop phenomenon is determined by the relationship between the characteristics of the lens provided in the imaging apparatus and the characteristics of the solid-state imaging device.

  Specifically, the peripheral light amount drop amount is uniquely determined by the relationship with the position of the solid-state imaging device with respect to the effective image circle (the region where the light hits uniformly). However, in this case, it is a premise that the effective pixel center of the solid-state imaging device and the optical axis center of the lens are coincident.

  In order to avoid this phenomenon, it is possible to use a lens in which the effective image circle of the lens provided in the imaging device is sufficiently large with respect to the imaging region of the solid-state imaging device. However, when a lens satisfying such conditions is used, the size of the lens itself becomes large, and it is difficult to reduce the size of the imaging device. As described above, when an imaging apparatus having a lens that is not sufficiently large is used to photograph a subject with a low contrast, a decrease in the amount of peripheral light becomes remarkable, which is a cause of a decrease in image quality.

  In view of this, there has been proposed a technique for correcting a peripheral light amount drop by compensating and flattening a light amount reduction characteristic from the center to the periphery of an image according to an aperture value (see Patent Document 1). In addition, a technique for correcting aberration and distortion caused by optical characteristics based on information from the photographing lens unit has been proposed (see Patent Document 2).

JP 2009-4967 A JP-A-5-158134

  However, the prior art disclosed in the above-mentioned patent document refers only to the taking lens.

  The same phenomenon can be said in the electronic viewfinder for observing the displayable area of the display that displays the image data through the eyepiece optical system. . If the lens is designed to be sufficiently large with respect to the displayable area of the display, the size of the lens itself becomes large, and it becomes difficult to reduce the size of the optical system (eyepiece optical system) of the electronic viewfinder. Further, when the lens is miniaturized, the inner diameter of the mask member for shielding stray light reflected on the end face of the optical component is reduced, and the peripheral light amount drop becomes remarkable.

  Accordingly, an object of the present invention is to reduce the influence of an optical system on an image, such as a decrease in peripheral light amount, with respect to an electronic viewfinder (EVF) displayed through an eyepiece optical system during shooting. It is another object of the present invention to provide an imaging apparatus that can provide a good live view image and that can reduce the size of an eyepiece optical system.

In order to achieve the above object, the present invention provides an image sensor,
Image processing means for correcting image data generated by the image sensor;
A first display (EVF) for displaying an image using the image data corrected by the image processing means;
An eyepiece optical system (eyepiece lens) provided for observing the first display;
The image processing means is an image pickup optical system (shooting) used to form a subject image on the image pickup device when the image pickup device generates the image data with respect to the image data generated by the image pickup device. First image correction based on the optical characteristics of the lens) and the optical characteristics of the eyepiece optical system (eyepiece lens),
The first display displays an image using image data on which the first light quantity drop correction is performed.

  According to the present invention, it is possible to improve the live performance by reducing the influence of the image by the optical system, such as a decrease in the amount of peripheral light, on the electronic viewfinder (EVF) displayed on the display through the eyepiece optical system at the time of shooting. It is possible to provide an imaging apparatus that can provide a view image and can reduce the size of the eyepiece optical system.

1 is a block diagram of a digital camera as an imaging apparatus according to an embodiment of the present invention. It is a flowchart which shows the procedure of the imaging (photographing) process which concerns on embodiment performed by the digital camera of FIG. It is a flowchart which shows the procedure of the reproduction | regeneration processing based on Embodiment performed by the digital camera of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Example 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a digital camera as an imaging apparatus according to an embodiment of the present invention. Hereinafter, the configuration will be described together with the operation.

  As shown in FIG. 1, a photographic lens unit 200 is detachably attached to the camera body 100 via a mount mechanism (not shown). The mount portion has a contact group 210. The contact group 210 transmits a control signal, a status signal, a data signal, and the like between the camera body 100 and the photographing lens unit 200. In addition, the contact group 210 also has a function of supplying currents of various voltages and a function of transmitting a signal to the microcomputer 120 when the photographing lens unit 200 is connected.

  Accordingly, communication can be performed between the camera body 100 and the photographing lens unit 200, and the photographing lens 201 and the diaphragm 202 in the attached photographing lens unit 200 can be driven. The contact group 210 may be configured to transmit not only electrical communication but also optical communication, voice communication, and the like.

  In the present embodiment, the photographing lens 201 is shown as a single photographing lens for the sake of convenience, but it is well known that the photographing lens 201 is actually composed of a larger number of lenses. The contact group 210 and the microcomputer 120 constitute lens detection means.

  Imaging light flux from a subject image (not shown) passes through an imaging lens 201 and an aperture 202, a focal plane shutter 108 as a mechanical shutter, and an image sensor 112 typified by a CMOS or the like as an imaging device as an imaging means. It reaches. The camera body 100 according to the present embodiment includes a microcomputer 120 that includes a CPU that controls the entire digital camera, and appropriately controls the operation of each unit described below. The microcomputer 120 corresponds to image processing means.

  The microcomputer 120 controls a lens control circuit 204 that controls a lens driving mechanism 203 for moving the photographing lens 201 in the optical axis direction and focusing, and an aperture driving mechanism 205 for driving the diaphragm 202. An aperture control circuit 206 is connected. The microcomputer 120 is connected to a shutter charge driving mechanism 110 that controls the shutter charge of the focal plane shutter 108. The microcomputer 120 is connected to a shutter control circuit 111 for controlling the traveling of the front and rear curtains of the focal plane shutter 108.

  The microcomputer 120 is connected to an EEPROM 122 which is a storage means. The EEPROM 122 includes parameters that need to be adjusted to control the camera body 100, camera ID information that enables individual identification of the digital camera, AF correction data adjusted by a reference lens, automatic exposure correction values, and an eyepiece optical system that will be described later. Optical characteristic data of the (eyepiece lens) 303 is stored.

  The optical characteristic data of the eyepiece optical system (eyepiece lens) 303 includes a correction table and the like necessary for correcting the peripheral light amount drop according to the distance from the final optical surface of the eyepiece lens 303, correcting the lateral chromatic aberration, and correcting the distortion aberration. included. In the present embodiment, the eyepiece 303 is shown as a single lens for convenience, but it is well known that it is actually composed of a larger number of lenses.

  The lens control circuit 204 also includes a lens storage device that stores lens-specific information, for example, information such as focal length, wide aperture, lens ID assigned to each lens, and information received from the system controller 120. Further, the microcomputer 120 controls the lens driving mechanism 203 to form a subject image adjusted in focus on the image sensor 112. Further, the microcomputer 120 controls the aperture driving mechanism 205 that drives the aperture 202 based on the set Av value, and further outputs a control signal to the shutter control circuit 111 based on the set Tv value. .

  An image data controller 115 is connected to the microcomputer 120. The image data controller 115 is configured by a DSP (digital signal processor), and executes control of the image sensor 112, correction and processing of image data input from the image sensor 112, and the like based on instructions from the microcomputer 120. is there.

  Further, the microcomputer 120 and the image data controller 115 constitute photometric means. The photometric means divides the image signal into regions by the image data controller 115, supplies the integrated value for each Bayer pixel in each region to the microcomputer 120, and performs photometry by evaluating the integrated signal with the microcomputer 120. .

  The image data controller 115 is connected to a timing pulse generation circuit 114 that outputs a pulse signal necessary for driving the image sensor 112. The image data controller 115 also includes an A / D converter 113 that receives the timing pulse generated by the timing pulse generation circuit 114 and converts an analog signal corresponding to the subject image output from the image sensor 112 into a digital signal. It is connected. The image data controller 115 is connected to a DRAM 121 for temporarily storing the obtained image data (digital data), a D / A converter 116, an image compression circuit 119, and a focus detection circuit 140.

  The DRAM 121 is used for temporarily storing image data before processing or data conversion into a predetermined format. Further, a recording medium 401 serving as a recording unit is connected to the image compression circuit 119. The image compression circuit 119 is a circuit for performing compression and conversion (for example, JPEG) of image data stored in the DRAM 121. The converted image data is stored in the recording medium 401. As this recording medium, a hard disk, a flash memory, or the like is used.

  The image data controller 115, the image compression circuit 119, and the recording medium 401 constitute a recording unit. In addition, an image display circuit 118 is connected to the D / A converter 116 via an encoder circuit 117. The image display circuit 118 is a circuit for displaying image data picked up by the image sensor 112, and is generally composed of a color display element.

  The image data controller 115 converts the image data on the DRAM 121 into an analog signal by the D / A converter 116 and outputs the analog signal to the encoder circuit 117. The encoder circuit 117 converts the output of the D / A converter 116 into an image signal (for example, an NTSC signal) necessary for driving the image display circuit 118. The D / A converter 116, the image display circuit 118, and the encoder circuit 117 constitute an image display means.

  The focus detection circuit 140 operates based on a command from the microcomputer 120. The focus detection circuit 140 evaluates contrast in a predetermined direction of an image signal obtained by performing predetermined gamma processing on the image data corrected by the image data controller 115 through an optical filter having a predetermined frequency characteristic. . The result is supplied to the microcomputer 120.

  The microcomputer 120 communicates with the lens control circuit 204, adjusts the focal position, and adjusts the focal position so that the contrast evaluation value is equal to or higher than a predetermined level and becomes the highest. The image data controller 115, the focus detection circuit 140, the system controller 120, the lens control circuit 204, the lens driving mechanism 203, and the taking lens 201 constitute a second automatic focus detection means.

  Further, the focus detection circuit 140 may detect the focus by a phase difference detection pixel (not shown) arranged on the imaging surface of the imaging element 112. The microcomputer 120 is connected to a release SW 1 (136) for starting a photographing preparation operation such as photometry and distance measurement. The microcomputer 120 is connected to a release SW 2 (137) for starting an imaging operation. Further, the microcomputer 120 is connected with an eye point selection SW 301 that allows the photographer to select whether to set the eye point short or long.

  The microcomputer 120 is connected to pupil position detection means 304 that can measure the distance of the photographer's pupil from the camera when the photographer is looking into the camera internal display 124. As a method for measuring the pupil distance by the photographer's pupil position detection unit 304, a known technique such as an image recognition function, a camera autofocus function, or a method using infrared reflection is used.

  The camera internal display 124 (the first display in the claims) and the camera back display 125 (the second display in the claims) are connected to the image display circuit 118, and the eyepiece connected to the microcomputer 120. The detection SW 302 detects whether or not the photographer is looking into the viewfinder by a sensor. The display 125 can be switched to a mode in which the display 125 can be directly observed by the image display circuit 118.

  FIG. 2 is a flowchart showing a procedure of imaging (photographing) processing according to the embodiment executed by the digital camera of FIG. This process is executed under the control of the microcomputer 120 in FIG.

  In FIG. 2, in step S101, the microcomputer 120 communicates with the photographing lens unit 200 via the contact group 210, proceeds to step S102, stores lens information in the EEPROM 122, and proceeds to step S103. The lens information includes a lens ID capable of discriminating the lens type, an aperture F value, a minimum aperture value, a focal length, exit pupil position information, and optical characteristics data of the photographing lens. . In addition, the optical characteristic data of the photographing lens unit 200 includes a correction table necessary for correcting the peripheral light amount drop, correcting the lateral chromatic aberration, and correcting the distortion.

  In step S103, the eyepiece detection SW 302 determines whether the photographer is looking into the camera internal display 124. If not, the process proceeds to step S115. If not, the process proceeds to step S104. In step S104, the microcomputer 120 reads out an image signal from the image sensor 112 and proceeds to step S105. In step S105, based on the optical characteristic data of the eyepiece lens 303 stored in the EEPROM 112, the image processing unit performs image correction on the image signal read in S104, and the process proceeds to step S106.

  In step S106, as in step S105, image correction is performed by the image processing unit based on the optical characteristic data of the photographing lens unit 200 stored in step S102, and the process proceeds to step S107. (The two image corrections in S105 and S106 are the first image corrections in the claims of the present invention.)

  As described above, the influence on the image such as a decrease in the amount of peripheral light, lateral chromatic aberration, and distortion due to the two optical systems of the eyepiece lens 303 and the photographing lens unit 200 is corrected. In step S107, the image data corrected in steps S105 and S106 is D / A converted by the D / A converter 116, encoded by the encoder circuit 117, and sequentially displayed on the camera internal display 124 via the image display circuit 118. In step S109, the state of the release SW1 (136) is confirmed. If it is in the OFF state, the process returns to step S103.

  By repeating the above processing, a live view is realized by displaying continuously read image signals on the camera internal display 124.

  If the state of the release SW1 (136) is ON in step S108, the process proceeds to step S109, and the microcomputer 120 reads an image signal from the image sensor 112 and proceeds to step S110. In step S110, image correction is performed based on the optical characteristic data of the photographing lens unit 200, and AF and AE are performed using the image signal, and the focus position and the exposure control value are held. In step S111, the state of release SW2 (137) is confirmed. If it is in the OFF state, the process returns to step S108.

  If it is in the ON state, the process proceeds to step S112 and the photographing operation is started. In step S112, Tv, Av, and ISO values at the time of shooting are determined according to the exposure control value calculated in step S110 and the state of the shooting mode. Then, through the shutter control circuit 111, the front curtain and the rear curtain are run at the determined Tv value, the image signal is read from the image sensor 112, and the process proceeds to step S114.

  In step S113, the image signal read in step S112 is subjected to image correction processing based on the optical characteristic data of the photographing lens unit 200 by the image processing means, and the image compression circuit 119 performs image conversion to JPEG or the like. After that, an image is recorded on the recording medium 401.

(The image correction performed in S113 based on only the optical characteristic data of the photographing lens unit 200 regardless of the optical characteristic data of the eyepiece lens 303 is referred to as a second image correction in the claims of the present invention.)
In the image recorded on the recording medium 401, the correction of the influence on the image by the optical system of the eyepiece lens 303 is overcorrected, and therefore image correction is performed based only on the optical characteristic data of the photographing lens unit 200.

In step S103 described above, when the photographer does not look into the camera internal display 124 by the eyepiece detection SW 302, the process proceeds to step S115.
In step S115, the microcomputer 120 reads out an image signal from the image sensor 112 and proceeds to step S116.

  In step S116, image correction is performed by the image processing means on the basis of the optical characteristic data of the photographing lens unit 200 stored in step S102 without depending on the optical characteristic data of the eyepiece 303 stored in the EEPROM 112, and the process proceeds to step S117. Transition.

  In step S117, the image data corrected in step S116 is D / A converted by the D / A converter 116, encoded by the encoder circuit 117, and sequentially displayed on the camera rear display 125 via the image display circuit 118. Migrate to In the image displayed on the camera rear display 125, the correction of the influence on the image by the optical system of the eyepiece lens 303 is overcorrected, and therefore image correction is performed based only on the optical characteristic data of the photographing lens unit 200. . The operation from step S108 is as described above.

  By repeating the above processing, when the photographer is looking into the camera internal display 124 by the eyepiece detection SW 302, the image signals read out continuously are stored in the optical system of the eyepiece lens 303 and the optical system of the photographing lens unit 200. It is possible to observe an image in which influences such as a decrease in peripheral light amount, lateral chromatic aberration, and distortion by the two optical systems are corrected.

  Further, when the photographer is not looking into the camera internal display 124, the photographer is directly viewing the image displayed on the camera back display 125 without going through the optical system of the eyepiece lens 303. Without being influenced by the system, it is possible to observe an image in which influences such as a decrease in peripheral light amount, lateral chromatic aberration, distortion, and the like due to only the optical system of the photographing lens unit 200 are corrected.

  FIG. 3 is a flowchart showing the procedure of the reproduction process according to the embodiment executed by the digital camera of FIG. This process is executed under the control of the microcomputer 120 in FIG.

  In FIG. 3, when a playback button (not shown) is pressed, an image playback sequence is executed. In step S201, the eyepiece detection SW 302 determines whether the photographer is looking into the camera internal display 124. If not, the process proceeds to step S205. If not, the process proceeds to step S202. In step S202, an image is read from the recording medium 401, and the process proceeds to step S202.

  In step S202, image correction is performed by the image processing unit 120 based on the correction data of the eyepiece, and the process proceeds to step S204 where the corrected image is displayed on the camera internal display 124. In step S205, an image is read from the recording medium 401, the process proceeds to step S206, and the image is displayed on the camera back display 125.

  During reproduction, since it is not affected by the optical system of the photographic lens unit 200, when the photographer is looking into the camera internal display 124, the peripheral light amount drop due to only the optical system of the eyepiece lens 303, chromatic aberration of magnification, distortion, etc. It is possible to observe an image with the effect corrected, and if the photographer is not looking into the camera internal display 124, the image is not affected by the optical system of the eyepiece lens 303, and thus the image is observed without image correction. Is possible.

  Since the influence of the optical system of the eyepiece lens 303 changes depending on the position of the photographer looking into the eyepiece lens 303, for example, when the photographer selects a short eyepoint using the eyepoint selection SW 301 described above, the eyepiece lens 303 stored in the EEPROM 112 is stored. If the photographer selects a long eye point from the optical data using the correction table corresponding to the short eye point position, the image correction is performed using the correction table corresponding to the long eye point position. Is possible.

  Further, by using the above-described pupil position detection means 304, image correction is performed using a correction table corresponding to the distance of the photographer's pupil from the camera when the photographer is looking into the camera internal display 124. Is possible.

  As described above, a good live view image can be obtained by reducing the influence of the ocular optical system such as a drop in peripheral light amount, lateral chromatic aberration, and distortion on the electronic viewfinder (EVF) displayed on the display through the eyepiece optical system. In addition, an imaging apparatus that can reduce the size of the eyepiece lens 303 in the displayable area of the camera internal display 124 can be provided.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, regarding the effect on the image received by the optical system of the eyepiece lens 303 when looking into the camera internal display 124, the light emission luminance of the camera internal display 124 is changed to the optical characteristic data of the eyepiece lens 303 with respect to the correction of the peripheral light amount drop. Based on this, for example, correction such as increasing the luminance only at the peripheral portion may be performed. In addition, when a peripheral device 500 having an optical system 501 for magnifying and observing the camera rear display 125 is attached, the peripheral device 500 has an influence such as a decrease in peripheral light amount, lateral chromatic aberration, distortion aberration, and the like. It is also possible to adopt a configuration in which an image displayed on the camera back display 125 is corrected so as to reduce it.

100 Camera body 108 Focal plane shutter 111 Shutter control circuit 112 Image sensor 113 A / D converter 114 Timing pulse generation circuit 115 Image data controller 116 D / A converter 117 Encoder circuit 118 Image display circuit 119 Image compression circuit 120 Microcomputer 121 DRAM
122 EEPROM
123 Operation display circuit 124 Camera internal display 125 Camera back display 136 Release SW1
137 Release SW2
140 Focus Detection Circuit 200 Lens Unit 201 Shooting Lens 202 Diaphragm 203 Lens Drive Mechanism 204 Lens Control Circuit 205 Diaphragm Drive Mechanism 206 Diaphragm Control Circuit 210 Contact Group 303 Eye Point Selection SW
303 Eyepiece optical system (eyepiece lens)
302 Eyepiece detection SW
303 eyepiece 304 pupil position detection means 401 recording medium 500 peripheral device

Claims (7)

An image sensor (112);
Image processing means (120) for correcting image data generated by the image sensor;
A first display (EVF) (125) for displaying an image using the image data corrected by the image processing means;
An eyepiece optical system (eyepiece lens) (303) provided for observing the first display;
The image processing unit (120) is an imaging optical unit that is used to form a subject image on the image sensor when the image sensor generates the image data with respect to the image data generated by the image sensor. Based on the optical characteristics of the system (photographing lens) (201) and the optical characteristics of the eyepiece optical system (eyepiece lens), the first image correction is performed,
The imaging apparatus according to claim 1, wherein the first display displays an image using the image data subjected to the first image correction. A second display (TFT) (124) for displaying an image using the image data corrected by the image processing means (120);
The image processing means (120) performs a second image correction based on the optical characteristics of the imaging optical system (201) without depending on the optical characteristics of the eyepiece optical system,
The imaging apparatus according to claim 1, wherein the second display displays an image using image data on which the second image correction has been performed. In accordance with a photographing instruction (137) from the photographer, the storage control means (119) for storing the image data in the memory (401) is provided.
The image processing means (120) performs a second image correction based on the optical characteristics of the imaging optical system (201) without depending on the optical characteristics of the eyepiece optical system,
The imaging apparatus according to claim 1, wherein the storage control unit (119) stores the image data subjected to the second image correction in the memory (401).   4. The imaging apparatus according to claim 1, wherein the first and second image corrections include at least one of peripheral light amount drop correction, lateral chromatic aberration correction, and distortion aberration correction. 5. .   Regarding the optical characteristics of the eyepiece optical system, a correction table of a plurality of optical characteristics data corresponding to the distance in the optical axis direction from the final optical surface of the eyepiece lens (303), and a setting eye of the eyepiece lens (303) according to a photographer's instruction An eye point selection SW (301) capable of changing the point position is provided, and the correction table for the optical characteristics of the eyepiece optical system is changed according to the result of the eye point selection SW (301) selected by the photographer. The imaging device according to any one of claims 1 to 4, wherein:   There is pupil position detecting means (304) for measuring the distance in the optical axis direction of the pupil looking into the photographer from the final optical surface of the eyepiece lens (303), and the detection result of the position in the optical axis direction of the pupil is obtained. 6. The imaging apparatus according to claim 1, wherein a correction table for optical characteristics of the eyepiece optical system is changed accordingly. A display (EVF) (125) for displaying image data;
An eyepiece optical system (eyepiece lens) (303) provided for observing the display;
An image pickup apparatus that corrects light emission luminance of the display (124) based on optical characteristics of the eyepiece optical system (eyepiece lens) (303).