JP2016129279A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which can detect and remove a frequency of flicker deviated minutely from 50 Hz or 60 Hz.SOLUTION: An imaging apparatus comprises: first flicker detection means; and second flicker detection means for detecting a flicker frequency with a prescribed frequency range in which the flicker frequency detected by the first flicker detection means is set to be a center as an object with resolution higher than that of a frequency detected by the first flicker detection means. A photographing control condition for display or recording for reducing occurrence of the flicker is determined based on the flicker frequency detected by the first flicker detection means, and then the photographing control condition is updated based on the flicker frequency detected by the second flicker detection means.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an imaging apparatus such as a camera, a digital camera, and a digital camera.

  In recent years, sensors having different exposure times for each line, such as CMOS sensors, are sometimes used as image sensors of digital cameras. In the case of the above-described sensor, flicker appears as surface flicker, and a horizontal stripe is generated, which is very unsightly as an image. Therefore, various ideas for detecting flicker and removing flicker are considered.

  In Patent Document 1, in a CMOS sensor in which the shutter speed and sensitivity can be changed for each line, the normal exposure control line and the exposure control line that is not affected by the flicker of the fluorescent lamp are alternately arranged. A technique is disclosed in which lines used for display or recording are switched according to the result of determining the presence or absence of flicker in two or more images that are configured.

Japanese Patent No. 531922

  However, in an environment where the power frequency is not stable, or even if the power frequency is stable, the flicker frequency slightly deviates from the reference 50 Hz or 60 Hz due to deterioration of a lighting device such as a fluorescent lamp. In the configuration in which flicker removal processing is performed by limiting the frequency to be performed to 50 Hz or 60 Hz, there is a problem that flicker cannot be completely removed.

  Japanese Patent Laid-Open No. 2004-228561 does not provide a configuration for performing flicker removal processing considering an environment in which the flicker frequency is slightly shifted from 50 Hz or 60 Hz as a reference.

  Accordingly, an object of the present invention is to provide an imaging apparatus capable of detecting and removing a flicker frequency slightly deviated from 50 Hz or 60 Hz.

In order to achieve the above object, an imaging apparatus of the present invention provides:
Targeting a predetermined frequency range centered on the flicker frequency detected by the first flicker detection means with a resolution higher than the resolution of the frequency detected by the first flicker detection means and the first flicker detection means A second flicker detection unit for detecting a flicker frequency, and after determining a display control or recording recording control condition for reducing the occurrence of flicker based on the flicker frequency detected by the first flicker detection unit; The imaging control condition is updated based on the flicker frequency detected by the second flicker detection means.

  According to the present invention, it is possible to provide an imaging apparatus capable of detecting and removing a flicker frequency slightly deviated from 50 Hz or 60 Hz.

It is a block diagram of a present Example. It is a schematic diagram of a present Example. It is a flowchart of a present Example. It is a 1st flicker detection flowchart of a present Example. It is a second flicker detection flowchart of the present embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. In FIG. 1, reference numeral 100 denotes an image processing apparatus. Reference numeral 10 denotes a photographing lens, 12 denotes a mechanical shutter having a diaphragm function, 14 denotes an image pickup device that converts an optical image into an electric signal, and 16 denotes an A / D converter that converts an analog signal output from the image pickup device 14 into a digital signal. .
A timing generation circuit 18 supplies a clock signal and a control signal to the image sensor 14, the A / D converter 16, and the D / A converter 26, and is controlled by the memory control circuit 22 and the system control circuit 50. In addition to the twelve mechanical shutters, the accumulation time can be controlled as an electronic shutter by controlling the reset timing of the fourteen imaging elements, and can be used for moving image shooting and the like.

  An image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on the data from the A / D converter 16 or the data from the memory control circuit 22. Further, an electronic zoom function is realized by performing image cutting and scaling processing by 20 image processing circuits. Further, the image processing circuit 20 performs predetermined calculation processing using the captured image data, and the system control circuit 50 controls the exposure control means 40 and the distance measurement control means 42 based on the obtained calculation result. TTL AAF processing, AE processing, and EF processing are performed. Further, the image processing circuit 20 performs predetermined arithmetic processing using captured image data, and also performs TTL AWB (auto white balance) processing based on the obtained arithmetic result.

  A memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32. The data of the A / D converter 16 is written into the image display memory 24 or the memory 30 via the image processing circuit 20 and the memory control circuit 22 or the data of the A / D converter 16 is directly passed through the memory control circuit 22. It is.

  Reference numeral 24 denotes an image display memory, 26 denotes a D / A converter, and 28 denotes an image display unit composed of a TFT LCD or the like. The display image data written in the image display memory 24 is converted into an image via the D / A converter 26. Displayed by the display unit 28. If the image data captured using the image display unit 28 is sequentially displayed, the electronic viewfinder function can be realized. The image display unit 28 can arbitrarily turn on / off the display according to an instruction from the system control circuit 50. When the display is turned off, the power consumption of the image processing apparatus 100 can be greatly reduced. I can do it.

Reference numeral 30 denotes a memory for storing captured still images and moving images, and has a sufficient storage capacity to store a predetermined number of still images and a predetermined time of moving images. Thereby, even in the case of continuous shooting or panoramic shooting in which a plurality of still images are continuously shot, it is possible to write a large amount of images to the memory 30 at high speed. The memory 30 can also be used as a work area for the system control circuit 50.
Reference numeral 32 denotes a compression / decompression circuit that compresses and decompresses image data by adaptive discrete cosine transform (ADCT) or the like, reads an image stored in the memory 30, performs compression processing or decompression processing, and stores the processed data in the memory 30. Write to.

  Reference numeral 40 denotes an exposure control means for controlling the shutter 12 having an aperture function, and has a flash light control function in cooperation with the flash 48.

  Reference numeral 42 denotes a distance measuring control means for controlling the focusing of the photographing lens 10, reference numeral 44 denotes a zoom control means for controlling zooming of the photographing lens 10, and reference numeral 46 denotes a barrier control means for controlling the operation of the protection means 102 as a barrier. A flash 48 has an AF auxiliary light projecting function and a flash light control function.

  The exposure control means 40 and the distance measurement control means 42 are controlled using the TTL method. Based on the calculation result obtained by calculating the captured image data by the image processing circuit 20, the system control circuit 50 performs the exposure control means 40 and the distance measurement. Control is performed on the control means 42.

  Reference numeral 50 denotes a system control circuit that controls the entire image processing apparatus 100, and reference numeral 52 denotes a memory that stores constants, variables, programs, and the like for operation of the system control circuit 50.

  Reference numeral 54 denotes a display unit such as a liquid crystal display device or a speaker that displays an operation state or a message using characters, images, sounds, or the like in accordance with execution of a program in the system control circuit 50. It is installed at a position where it can be easily seen in the vicinity of the unit, and is composed of, for example, a combination of an LCD, an LED, a sound generation element, and the like. The display unit 54 has a part of its function installed in the optical viewfinder 104.

  Among the display contents of the display unit 54, what is displayed on the LCD or the like includes single shot / continuous shooting display, self-timer display, compression rate display, recording pixel number display, recording number display, remaining image number display, shutter There are speed display, aperture value display, exposure compensation display, flash display, red-eye reduction display, macro shooting display, etc. Further, a buzzer setting display, a battery remaining amount display, an error display, an information display with a multi-digit number, an attachment / detachment state display of the recording media 200 and 210, a communication I / F operation display, and the like are also possible. Among the display contents of the display unit 54, what is displayed in the optical viewfinder 104 includes in-focus display, camera shake warning display, flash charge display, shutter speed display, aperture value display, exposure correction display, and the like.

  Reference numeral 56 denotes an electrically erasable / recordable nonvolatile memory such as an EEPROM.

  Reference numerals 60, 62, 64, 66, 70, 72, and 74 denote operation means for inputting various operation instructions of the system control circuit 50, such as switches, dials, touch panels, pointing by line-of-sight detection, voice recognition devices, and the like. Consists of a single or a plurality of combinations.

  Here, a specific description of these operating means will be given. Reference numeral 60 denotes a mode dial switch which switches between power off, automatic shooting mode, shooting mode, panoramic shooting mode, movie shooting mode, playback mode, multi-screen playback / erase mode, PC connection mode, TV reception mode, etc. I can do it.

  Reference numeral 62 denotes a shutter switch SW1, which is turned ON during the operation of the shutter button and starts operations such as AF (auto focus) processing, AE (auto exposure) processing, AWB (auto white balance) processing, and EF (flash pre-flash) processing. Instruct.

  A shutter switch SW2 64 is turned on when the operation of the shutter button is completed. Exposure processing for writing the image data into the memory 30 via the A / D converter 16 and the memory control circuit 22 for the signal read from the image sensor 12, development processing using arithmetic operations in the image processing circuit 20 and the memory control circuit 22, The image data is read from the memory 30 and compressed by the compression / decompression circuit 32. Next, the start of a series of processing operations such as recording processing for writing the image data to the recording medium 200 or 210 is instructed.

  Reference numeral 66 denotes a display changeover switch, which can change the display of the image display unit 28. With this function, when photographing using the optical viewfinder 104, it is possible to save power by cutting off the current supply to the image display unit such as a TFTLCD.

  An operation unit 70 includes various buttons and a touch panel, and includes a menu button, a set button, a macro button, a multi-screen playback page break button, a flash setting button, a single shooting / continuous shooting / self-timer switching button, and the like. Menu move + (plus) button, menu move-(minus) button, playback image move + (plus) button, playback image-(minus) button, shooting quality selection button, exposure compensation button, date / time setting button, etc. is there.

  Reference numeral 72 denotes a zoom switch unit as zoom operation means for a user to instruct a magnification change of a captured image. Hereinafter, the zoom switch 72 is also referred to. The zoom switch 72 includes a tele switch that changes the imaging field angle to the telephoto side and a wide switch that changes the imaging angle of view to the wide angle side. By using the zoom switch 72, the zoom control unit 44 is instructed to change the imaging field angle of the photographing lens 10 and becomes a trigger for performing an optical zoom operation. In addition, it also serves as a trigger for electronic change of the imaging angle of view by image cutting by the image processing circuit 20 or pixel interpolation processing. Reference numeral 74 denotes a subject detection unit, which includes an element for detecting a subject. A case where a person's face is detected as a subject is also conceivable.

  Reference numeral 80 denotes a power control means, which includes a battery detection circuit, a DC-DC converter, a switch circuit for switching a block to be energized, and the like, and detects whether or not a battery is installed, the type of battery, and the remaining battery level. Further, the DC-DC converter is controlled based on the detection result and the instruction of the system control circuit 50, and a necessary voltage is supplied to each part including the recording medium for a necessary period.

  Reference numeral 82 denotes a connector, 84 denotes a connector, and 86 denotes a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a Li battery, an AC adapter, or the like.

  Reference numerals 90 and 94 denote interfaces with recording media such as memory cards and hard disks, and reference numerals 92 and 96 denote connectors for connecting to recording media such as memory cards and hard disks.

  In this embodiment, it is assumed that there are two interfaces and connectors for attaching the recording medium. Of course, the interface and the connector for attaching the recording medium may have a single or a plurality of systems and any number of systems. Moreover, it is good also as a structure provided with combining the interface and connector of a different standard.

  The interface and connector may be configured using a PCMCIA card, a CF (Compact Flash (registered trademark)) card, or the like that conforms to a standard. Further, the interfaces 90 and 94, and the connectors 92 and 96 can be configured by using ones conforming to a standard such as a PCMCIA card or a CF (compact flash) card. That is, by connecting various communication cards such as LAN cards, modem cards, USB cards, IEEE 1394 cards, SCSI cards, PHS and other communication cards, image data and images can be exchanged with other computers and peripheral devices such as printers. Management information attached to the data can be transferred.

  Reference numeral 102 denotes protection means that is a barrier that prevents the imaging unit from being soiled or damaged by covering the imaging unit including the lens 10 of the image processing apparatus 100.

  Reference numeral 104 denotes an optical viewfinder, which can take an image using only the optical viewfinder without using the electronic viewfinder function of the image display unit 28. In the optical viewfinder 104, some functions of the display unit 54, for example, a focus display, a camera shake warning display, a flash charge display, a shutter speed display, an aperture value display, an exposure correction display, and the like are installed.

  A communication unit 110 has various communication functions such as RS232C, USB, IEEE1394, P1284, SCSI, modem, LAN, and wireless communication.

  Reference numeral 112 denotes a connector for connecting the image processing apparatus 100 to another device by the communication unit 110 or an antenna in the case of wireless communication.

  Reference numeral 200 denotes a recording medium such as a memory card or a hard disk. The recording medium 200 includes a recording unit 202 composed of a semiconductor memory, a magnetic disk, or the like, an interface 204 with the image processing apparatus 100, and a connector 206 for connecting to the image processing apparatus 100.

  Reference numeral 210 denotes a recording medium such as a memory card or a hard disk. The recording medium 210 includes a recording unit 212 composed of a semiconductor memory, a magnetic disk, or the like, an interface 214 with the image processing apparatus 100, and a connector 216 that connects to the image processing apparatus 100.

  FIG. 2 is a diagram for explaining the outline of the embodiment of the present invention. As shown in FIG. 2A, for example, the brightness of illumination changes at 120 Hz under a fluorescent lamp with a power supply frequency of 60 Hz. In this case, flickering occurs when the electronic shutter is other than a multiple of 120 Hz = 1/120 seconds during moving image shooting of the digital camera or in the finder display state displayed with the electronic finder. In particular, in the case where the image sensor 14 has a different accumulation time for each line, such as a CMOS sensor, the brightness differs for each line, which generates horizontal stripes, resulting in a very unsightly image.

  Therefore, in this embodiment, the accumulation time is changed for each line, images with different shutter speeds are generated, and an image without flicker is used as a display or recording image. The flowchart is shown in FIG. 3 and FIG. 3 and 4 are flowcharts for explaining the imaging processing operation of the digital camera 100. FIG.

  In step S301, when the shutter switch SW162 is pressed when the mode dial switch 60 is in the moving image shooting mode, photometry is performed in step S302 to determine the exposure condition to be set by the camera. In this embodiment, the ISO sensitivity is ISO200, the shutter speed is 1/80, and the aperture is f2.8 (S303). In the present embodiment, for the sake of simplicity, photometry is performed once before shooting. However, it goes without saying that photometry is always performed even during moving image shooting. Further, the shutter speed set in step S303 is hereinafter referred to as ss1.

  In step S304, it is determined whether or not the flicker detection mode is set. However, the user can detect flicker by using a menu or operation means such as 60, 62, 64, 66, 70, 72 and 74 displayed on the display unit 54. It is possible to set whether or not the mode. If the flicker detection mode is not set in step S304, moving image shooting is started in step S306. If the flicker detection mode is set, moving image shooting is started in step S305.

  In step S307, immediately after moving image shooting is started, coarse flicker detection is set in order to eliminate the noticeable flicker. Specifically, it is a setting for performing flicker detection with respect to a commercial power supply frequency of 50 Hz or 60 Hz. Here, ss2 and ss3 are shutter speeds with respect to the flicker frequency that is a flicker detection target. That is, in the coarse flicker detection setting, ss2 = 1/60 and ss3 = 1/50 are set.

  In step S308, the shutter speed and gain are changed for each line. In step S309, when the line number is a remainder obtained by dividing by 3 (N = 1, 4, 7,...), The line is not changed from the exposure condition determined in step S303. That is, the ISO sensitivity is maintained at ISO 200, the shutter speed is 1/80 second (ss1), and the aperture f2.8 is maintained (S3101).

  In step S311, when the line number is divided by 3 and the number is 2 (N = 2, 5, 8,...), The shutter speed is changed to 1/60 seconds (ss2), and the shutter speed is set to 1. The gain is lowered by 1/3 by the amount changed to / 3-stage overexposure, and ISO 160 is set (step S312). This keeps the screen brightness the same.

  Similarly, in step S313, if the remaining line, that is, the line number is divisible by 3 (N = 3, 6, 9,...), The shutter speed is changed to 1/50 second (ss3). The gain is lowered by 2/3 of the amount corresponding to the overshoot of the 2/3 step exposure at the shutter speed to ISO128 (step S314).

  The above is repeated, so that lines of shutter speed 1/80 second (ss1), 1/60 second (ss2), and 1/50 second (ss3) are alternately arranged in one screen (however, by correcting with a gain) , Brightness is uniform). When this repetition is completed in step S315, exposure is started in step S317, and a video signal is read in S318.

  In step S319, if it is a rough flicker detection setting, the process proceeds to adopted image determination 1 in step S320, and if it is a fine flicker detection setting, the process proceeds to adopted image determination 2 in step S321. As an outline of the adopted image determination, three images obtained by distributing lines for each shutter speed line are extracted from the image read in step S318 (step S402 in FIG. 4), and the presence or absence of flicker is determined. A process of selecting the extracted image having the smallest flicker influence as a display image or a recording image is performed.

  This is illustrated in FIG. 2 (a). Normally, the number of vertical lines is 1/3 compared to an image obtained by reading out one screen without changing the shutter speed for each line. With the recent increase in the number of pixels in the image sensor, it is considered that an image with sufficient quality can be obtained even when the number of lines is reduced to 1/3, and almost the same image can be obtained for all three. it can.

  A flowchart of adopted image determination 1 in step S320 is shown in FIG. 4, and a flowchart of adopted image determination 2 in step S321 is shown in FIG.

  By the processing up to step S320, the flicker countermeasure for 50 Hz or 60 Hz serving as a reference depending on the commercial power supply frequency can be read and performed in a short time. In order to detect residual flicker due to a minute frequency shift, the setting for fine flicker detection is performed in step S322. Here, ss1 sets the shutter speed of the image selected in step S320 or step S321. ss2 and ss3 are set to values within a predetermined range with the shutter speed of ss1 as the center, but are updated by changing them sequentially to be constant, or as shown in FIG. A shifted shutter speed is set, and a shutter speed with a half of the predetermined shift amount as a shift amount is set for each update timing. With such a configuration, flicker detection can be performed with higher resolution. In step S323, it is determined whether or not the moving image shooting is completed. If the moving image shooting is ended, the moving image shooting is ended (step S324).

  A flowchart of the adopted image determination 1 in FIG. 4 will be described.

  When the specific regions (slightly narrow regions near the center) of the video signals of the three types of images obtained in step S403 are integrated, and all the integration results match in step S404 (or the difference of a certain threshold value or less) In this case, it is determined that no flicker has occurred in all the images (step S407). The exposure conditions obtained by the first photometry are ISO sensitivity ISO200, shutter speed 1/80 seconds (ss1), and aperture. The image of f2.8 is adopted as the shooting moving image (step S408).

  If all the integration results do not match in step S404 (or if the difference is greater than a certain threshold), it is determined in step S405 that any image has flicker. The adopted image determination 1 is intended to detect / remove flicker under a fluorescent lamp. In this case, the frequency of the fluorescent lamp is 50 Hz or 60 Hz, and the image has a shutter speed of 1/50 seconds and the shutter speed. It can be determined that no flicker occurs in either of the 1/60 second images. In this case, first, in step S40, the flicker component is extracted by subtracting the signal of the image having the shutter speed 1/50 seconds and the image having the shutter speed 1/60 seconds in the integration area.

  In step S409, when the flicker component is subtracted from the image with a shutter speed of 1/50 seconds and compared with the image with a shutter speed of 1/60 seconds, the signals match (or when the difference is less than a certain threshold). Then, it is determined that no flicker occurs in an image with a shutter speed of 1/60 seconds (step S413), and in step S414, an image with a shutter speed of 1/60 seconds is adopted as a captured moving image. If they do not match in step S409 (or if the difference is greater than a certain threshold), the flicker component is subtracted from the image with a shutter speed of 1/60 seconds, and compared with the image with a shutter speed of 1/50 seconds, The signals coincide with each other (step S410), and it is determined that no flicker occurs in the image with the shutter speed of 1/50 seconds (step S411). In step S412, the image with the shutter speed of 1/50 seconds is captured. Adopt as. Through the above steps, an image in which no flicker has occurred or in which flicker has been reduced can be adopted as a captured moving image. In step S415, image determination ends.

  A flowchart of the adopted image determination 2 in FIG. 5 will be described.

  In step S502, an image is created by extracting three images in which lines are assigned for each shutter speed line from the image read in step S318 in FIG. In step S503, a flickerless image serving as a comparison reference in the flicker detection of the extracted image is created. Specifically, it depends on a method of creating an average image of the extracted images for a plurality of frames. In this step, since there is no noticeable flicker in the display or captured image, it is possible to employ a process that takes time such as requiring a plurality of frames.

  In step S504, the flickerless image is subtracted from each of the ss1, ss2, and ss3 images to extract the flicker component of each image, and the image having the smallest flicker component is adopted as a captured moving image (step S505). The speed is reset to ss1 (step S506).

  In step S507, if the flicker component of the image having the smallest flicker component is smaller than a predetermined value, the flicker detection is terminated (step S508). Otherwise, ss2 and ss3 are reset based on ss1 (step 509). . As described above, the resetting may be performed by updating the value within a predetermined range centered on the shutter speed of ss1 by sequentially changing the value continuously, or by updating the value by sequentially reducing the predetermined shift amount by half.

  The flicker detection method in FIG. 4 of the adopted image determination 1 is merely an example. For example, a line of shutter speed 1/120 seconds is added to the above embodiment, and shutter speed 1/50 seconds and shutter speed 1 / It is also possible to easily detect the flicker image by comparing the integral values of the 60-second line image. Further, as described above, it is needless to say that the present embodiment can be applied even when the photometry is always performed during moving image shooting and the appropriate exposure changes. Although this embodiment is an embodiment for a captured image during moving image shooting, this embodiment can be applied to an image using an electronic shutter such as a display image when displaying an electronic viewfinder for a still image. It is.

  As described above, according to the imaging apparatus to which the present invention is applied, it is possible to provide an imaging apparatus that can detect and remove the flicker frequency slightly deviated from 50 Hz or 60 Hz.

10 photographing lens, 12 shutter, 14 image sensor, 16 A / D converter,
18 timing generation circuit, 20 image processing circuit, 22 memory control circuit,
24 image display memory, 26 D / A converter, 28 image display unit, 30 memory,
32 image compression / decompression circuit, 40 exposure control means, 42 distance measurement control means,
44 zoom control means, 46 barrier control means, 48 flash,
50 system control circuit, 52 memory, 54 display unit, 56 non-volatile memory,
60 mode dial switch, 62 shutter switch SW1,
64 Shutter switch SW2, 66 Display changeover switch, 70 Operation unit,
72 zoom switch, 74 subject detection unit, 80 power control means, 82 connector,
84 connector, 86 power supply means, 90 interface, 92 connector,
94 interface, 96 connector, 100 image processing apparatus, 102 protection means,
104 optical viewfinder, 110 communication means, 112 connector (or antenna),
200 recording medium, 202 recording unit, 204 interface, 206 connector,
210 recording medium, 212 recording unit, 214 interface, 216 connector

Claims (3)

Targeting a predetermined frequency range centered on the flicker frequency detected by the first flicker detection means with a resolution higher than the resolution of the frequency detected by the first flicker detection means and the first flicker detection means A second flicker detection means for detecting a flicker frequency;
The flicker frequency detected by the second flicker detection means after determining shooting or display control conditions for reducing the occurrence of flicker based on the flicker frequency detected by the first flicker detection means An imaging apparatus, wherein the imaging control condition is updated based on: 2. The second flicker detection unit performs flicker detection by constantly changing a predetermined frequency range centered on the flicker frequency detected by the first flicker detection unit. Imaging device. The second flicker detection means performs flicker detection on a frequency shifted by a predetermined amount centered on the detected flicker frequency, selects a smaller flicker, and performs the predetermined shift until the flicker becomes a predetermined value or less. The imaging apparatus according to claim 1, wherein flicker detection is repeated with the amount set to half.