JP2006332917A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an occurrence period of flicker, i.e. a commercial power frequency by means of simple hardware and software configurations. <P>SOLUTION: A control section 4 generates data of an increase/decrease in integration data L(n) between adjacent frames stored in a memory, when the integration data of a frame are greater than the integration data of its preceding frame, the control section 4 produces a (+) code, when smaller, the control section 4 produces a (-) code, so as to produce a (+), (-) increase/decrease pattern of the data, and the control section 4 stores the data of the increase/decrease pattern to a memory. The control section 4 compares the increase/decrease pattern with contents of an increase/decrease pattern table comprising the increase/decrease pattern when a flicker frequency is 100Hz and the increase/decrease pattern when a flicker frequency is 120Hz, so that the control section 4 judges whether the pattern of the flicker frequency is coincident with the increase/decrease pattern of the flicker frequency of 100Hz or the increase/decrease pattern of the flicker frequency of 120Hz. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging system technology using an imaging device, and more particularly to a technology effective for detecting flicker caused by frequency fluctuation caused by a power supply frequency included in illumination light.

  As an image sensor used for a digital camera, a camera-equipped mobile terminal, and the like, for example, a complementary metal oxide semiconductor (CMOS) image sensor is widely known.

  The CMOS type image pickup device is said to cause a so-called fluorescent light flicker when a picture is taken in a room where a fluorescent light is lit or the like, and a horizontal stripe flicker with a non-uniform luminance level according to the blinking cycle of the fluorescent light. There's a problem.

  This fluorescent lamp flicker does not occur if the charge accumulation time of each pixel of the image sensor matches an integer multiple of the blinking cycle of the fluorescent lamp. For this reason, flicker suppression techniques are (1) broadly divided by the variable gain amplifier to cancel the horizontal stripe-like nonuniformity caused by the flicker, and (2) the charge accumulation time of the image sensor is an integral multiple of the blinking cycle of the fluorescent lamp. In principle, it is possible to prevent flicker from occurring.

  In any of the techniques (1) and (2) described above, it is important to recognize the flicker generation period to be suppressed, that is, the commercial power supply frequency. In particular, the frequency ( In Japan where 60 Hz / 50 Hz is different, a more reliable detection technique is required.

As a technology for recognizing the above-mentioned commercial power supply frequency and reducing flicker in the image sensor, a technique for estimating the commercial power supply frequency using GPS (for example, Patent Document 1), or in accordance with the period of the horizontal band caused by flicker. There is a technique in which a plurality of detection frames are provided in the vertical direction in the screen, and the frequency is determined from detection value fluctuations for each detection frame (for example, Patent Document 2).
JP 2003-60984 A JP 2003-189129 A

  However, the present inventor has found that the flicker reduction technology in the CMOS image sensor as described above has the following problems.

  In other words, the commercial power supply frequency estimation technique disclosed in Patent Document 1 has a problem that the use of GPS complicates the configuration of a photographing apparatus such as a digital camera, increases the size, and becomes very expensive.

  Further, the commercial power supply frequency determination technique disclosed in Patent Document 1 requires a plurality of detection frames for flicker detection, which causes a problem that the apparatus configuration is complicated and the cost is increased.

  An object of the present invention is to provide a technique for detecting a flicker generation period, that is, a commercial power supply frequency by hardware and software having a simple configuration.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  An imaging apparatus according to the present invention includes a flicker detection unit that performs flicker detection based on a luminance signal included in an imaging signal output from a solid-state imaging device in a flicker detection region in which an image is divided into arbitrary regions in the vertical scanning direction; A flicker frequency determination unit that determines a flicker frequency from detection data detected by the flicker detection unit, and the flicker frequency determination unit uses the detection data detected by the flicker detection unit to increase or decrease a luminance change pattern for each frame. And flicker frequency is determined from the increase / decrease pattern.

  Moreover, the outline | summary of the other invention of this application is shown briefly.

  In the imaging apparatus according to the present invention, the flicker detection area in which the flicker detection unit detects flicker has a time difference of 1/120 second or less between the scanning time of the first pixel in the flicker detection area and the scanning time of the last pixel in the flicker detection area. Is set to be.

  In the imaging apparatus of the present invention, the flicker frequency determination unit calculates integration data obtained by integrating the flicker detection signal flicker detected by the flicker detection unit, and the integration data calculated by the integration processing unit. An integral data storage unit that stores a plurality of frames, a pattern storage unit that stores increase / decrease patterns of luminance changes that occur when the flicker frequency is 100 Hz and 120 Hz, and an interval between adjacent frames stored in the integral data storage unit The integration data is respectively compared to generate increase / decrease pattern data, and whether the increase / decrease pattern data matches the increase / decrease pattern with the flicker frequency stored in the pattern storage unit of 100 Hz or the increase / decrease pattern with the flicker frequency of 120 Hz. A determination unit that determines the flicker frequency by determining Those were example.

  Furthermore, the image pickup apparatus of the present invention is provided with a plurality of flicker detection areas in which the flicker detection unit detects flicker.

  In the image pickup apparatus of the present invention, the flicker detection region in which the flicker detection unit detects flicker moves the image in the vertical scanning direction at an arbitrary cycle.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  (1) Flicker due to an illumination light source such as a fluorescent lamp can be automatically determined by a simple hardware configuration and software configuration.

  (2) According to the above (1), the performance can be improved while reducing the cost of the imaging device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is a block diagram of an image pickup apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram schematically showing a time change of illuminance by a fluorescent lamp in a commercial power supply frequency 50 Hz / 60 Hz region, and FIG. FIG. 4 is an explanatory diagram showing a change in luminance for each frame at a specific position on the screen when the frame period is 17 fps (58.8 msec), and FIG. 4 is an explanatory diagram showing an example of a detection frame in the imaging apparatus of FIG. FIG. 5 is a flowchart showing an example of flicker determination processing in the imaging apparatus of FIG.

  In the present embodiment, the imaging device 1 is composed of, for example, a camera system for a CMOS type solid-state imaging device. As shown in FIG. 1, the imaging apparatus 1 includes a CMOS solid-state imaging device (individual imaging device) 2, a signal processing unit 3, and a control unit (flicker frequency determination unit, integration processing unit, determination unit) 4. Yes.

  The CMOS type solid-state imaging device 2 converts the image formed by the lens into a voltage signal and outputs it based on the synchronization signal. A signal processing unit 3 is connected to the CMOS solid-state imaging device 2.

  The signal processing unit 3 includes a semiconductor integrated circuit device such as a DSP (Digital Signal Processor), and processes the image signal output from the CMOS solid-state imaging device 2.

  The signal processing unit 3 includes an image processing circuit 5, a synchronization circuit 6, a detection circuit (flicker detection unit) 7, and the like. The image processing circuit 5 performs image processing on the image signal output from the CMOS type solid-state imaging device 2 and displays it on a display or the like. The synchronization circuit 6 generates a synchronization signal and outputs it to the CMOS solid-state imaging device 2. The detection circuit 7 performs flicker detection and outputs a detection signal to the control unit 4.

  The control unit 4 is composed of, for example, a microcomputer, and controls the operation of the CMOS solid-state imaging device 2 and the signal processing unit 3, and uses a commercial power source based on the detection signal output from the detection circuit 7. Determine frequency and remove flickering flicker.

  Next, the operation of the imaging device 1 according to this embodiment will be described.

  First, the principle of flicker will be described.

  FIG. 2 is an explanatory diagram schematically showing a time change of illuminance by a fluorescent lamp in a commercial power supply frequency 50 Hz / 60 Hz region.

  As shown in the figure, the fluorescent lamp repeatedly blinks (flicker frequency) at a frequency twice the commercial power supply frequency. The actual change in illuminance changes in a complex manner depending on the afterglow characteristics of the fluorescent lamp itself and the influence of reflected light in the imaging environment. Ideally, when the power supply frequency is 50 Hz (flicker cycle 100 Hz), y = | Sin (100π (t / 1000 |). In the case of a commercial power supply frequency of 60 Hz (flicker cycle 120 Hz), it changes with a curve of y = | sin (120π (t / 1000 |). T = msec.

  Since the imaging apparatus 1 repeats imaging continuously at a certain frame period, when the frame period is not 100 Hz or an integer multiple of 120 Hz, naturally, the imaging frame period and the illuminance change period are set for each imaging frame. The phase difference will change. This appears as a symptom in which the horizontal band-like luminance change scrolls on the screen.

  FIG. 3 is an explanatory diagram showing a change in luminance for each frame at a specific position on the screen when the frame period is 17 fps (58.8 msec).

  In this case, the increase and decrease are repeated every 9 frames at a commercial power supply frequency of 50 Hz (flicker frequency of 100 Hz), and the increase and decrease are repeated every 17 frames from 17 frames at a commercial power supply frequency of 60 Hz (flicker frequency of 120 Hz).

  Therefore, by intentionally setting the frame period so that the horizontal band-like luminance change is scrolled, each frame of the detection data is detected from the detection frame (flicker detection region) KP (FIG. 4) whose position in the screen is fixed. The flicker generation period, that is, the commercial power supply frequency is determined from the increase / decrease change.

  The detection frame KP is set to an arbitrary section within one frame, and the determination is performed by using the integrated data obtained by detecting the luminance signal in the detection frame KP as a detection signal by the detection circuit 7 and integrating the detection signal. .

  FIG. 4 is an explanatory diagram showing an example of the detection frame KP.

  The width of the detection frame KP in the vertical direction is set to, for example, 8.33 msec (corresponding to 1/120 second) or less in one frame. For example, if the detection frame KP is made large in the vertical direction of the frame, it will cross a plurality of signal amount fluctuation peaks in that section, and the detection accuracy of the signal change for each frame will decrease due to the integration effect. become. This value is about 14% or less in the vertical direction (58.8 msec) of the frame when the frame period is 17 fps.

  FIG. 5 is a flowchart illustrating an example of flicker determination processing in the imaging apparatus 1.

  The determination process flow in FIG. 5 is started, for example, in a frame cycle.

  First, at the start of a frame, when the detection signal subjected to flicker detection by the detection circuit 7 is input to the control unit 4 (step S101), the number of frames of the detection data is incremented (n = n + 1) (step S102). .

  Subsequently, it is determined whether or not the number of frames n is larger than a predetermined value (m). If the number of frames n is larger than a numerical value (m), the value of n is reset to 1. (Step S103).

  Then, the control unit 4 calculates integrated data L (n) from the detected signal (step S104). The control unit 4 stores the calculated integration data in a memory (integration data storage unit, pattern storage unit) provided in the control unit 4. This memory is a so-called ring buffer, and stores integration data L (n) over several frames (1 to m) in the past.

  The control unit 4 creates data indicating increase / decrease of the integration data L (n) between adjacent frames stored in the memory (step S105). In the process of step S105, if the integral data L (n) of a certain frame is larger than the integral data L (n-1) of the previous frame, it is set as (+), and when it is small, it is set as (-). The (+) and (-) increase / decrease patterns (increase / decrease pattern data) of the data are generated, and the increase / decrease pattern data is stored in the memory of the control unit 4 described above.

  The memory of the control unit 4 stores an increase / decrease pattern table in advance. This increase / decrease pattern table includes an increase / decrease pattern when the flicker frequency is 100 Hz and an increase / decrease pattern when the flicker frequency is 120 Hz.

  Then, the control unit 4 compares the increase / decrease pattern table stored in the memory with the increase / decrease pattern generated in the process of step S105 (step S106), and the increase / decrease of either the flicker frequency is 100 Hz or the flicker frequency is 120 Hz. It is determined whether the pattern matches (step S107).

  If it matches the flicker frequency increase / decrease pattern of any one of 100 Hz / 120 Hz, the determined frequency (100 Hz or 120 Hz) is used as the flicker frequency for provisional determination (step S108).

  Thereafter, it is determined whether or not the flicker frequency tentatively determined in the process of step S108 continuously matches a predetermined number of frames (step S109). The frequency is determined as the final flicker frequency (step S110).

  Then, the control unit 4 prevents the occurrence of flicker by controlling the charge accumulation time of the CMOS type solid-state imaging device 2 to an integral multiple of the flicker frequency determined in the process of step S110.

  As a result, according to the present embodiment, the flicker generation period, that is, the commercial power supply frequency can be easily determined from one detection frame KP, thereby simplifying the hardware and software configuration of the imaging apparatus 1. can do.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the above-described embodiment, the case where the detection frame is fixed has been described. However, as shown in FIG. 6, flicker fringes generated by a fluorescent lamp by moving the detection frame KP from the upper side to the lower side of the frame at a fixed period. May be detected.

  Further, as shown in FIG. 7, a plurality of detection frames KP may be provided for the frame, and the horizontal stripes generated by the flicker may be detected.

  INDUSTRIAL APPLICABILITY The present invention is suitable for a flicker / flicker detection technique caused by frequency fluctuations caused by a power supply frequency included in illumination light in an imaging system using an imaging device.

1 is a block diagram of an imaging apparatus according to an embodiment of the present invention. It is explanatory drawing which showed typically the time change of the illumination intensity by the fluorescent lamp in a commercial power supply frequency 50Hz / 60Hz area. It is explanatory drawing which showed the luminance change for every flame | frame in the specific position on a screen when a frame period is 17 fps (58.8 msec). It is explanatory drawing which showed an example of the detection frame in the imaging device of FIG. 3 is a flowchart illustrating an example of flicker determination processing in the imaging apparatus of FIG. 1. It is explanatory drawing which showed an example of the detection frame in the imaging device by other embodiment of this invention. It is explanatory drawing which showed the other example of the detection frame in the imaging device by other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 CMOS type solid-state image sensor (solid-state image sensor)
3 Signal processing unit 4 Control unit (flicker frequency determination unit, integration processing unit, determination unit)
5 Image processing circuit 6 Synchronous circuit 7 Detection circuit (flicker detection unit)

Claims (5)

A flicker detection unit that performs flicker detection based on a luminance signal included in an imaging signal output from a solid-state imaging device in a flicker detection region obtained by dividing an image into arbitrary regions in the vertical scanning direction;
A flicker frequency determination unit for determining a flicker frequency from detection data detected by the flicker detection unit;
The flicker frequency determination unit
An imaging apparatus characterized by generating a luminance change increase / decrease pattern for each frame from detection data detected by the flicker detection unit and determining a flicker frequency from the increase / decrease pattern. The imaging device according to claim 1,
The flicker detection area where the flicker detection unit detects flicker is
An imaging apparatus, wherein a time difference between a scanning time of a first pixel in the flicker detection area and a scanning time of a tail pixel in the flicker detection area is set to be 1/120 second or less. The imaging apparatus according to claim 1 or 2,
The flicker frequency determination unit
An integration processing unit for calculating integration data obtained by integrating the flicker detection signal flicker detected by the flicker detection unit;
An integration data storage unit for storing the integration data calculated by the integration processing unit for a plurality of frames;
A pattern storage unit that stores increase / decrease patterns of luminance changes that occur when the flicker frequency is 100 Hz and 120 Hz,
The integration data is compared between adjacent frames stored in the integration data storage unit to generate increase / decrease pattern data, and the increase / decrease pattern data is stored in the pattern storage unit and the flicker frequency is 100 Hz. An image pickup apparatus comprising: a determination unit that determines a flicker frequency by determining which of the increase / decrease patterns of 120 Hz coincides with the flicker frequency. The imaging device according to any one of claims 1 to 3,
An image pickup apparatus comprising a plurality of flicker detection areas in which the flicker detection unit detects flicker. The imaging device according to any one of claims 1 to 3,
The flicker detection area where the flicker detection unit detects flicker is
An image pickup apparatus that moves an image in a vertical scanning direction at an arbitrary cycle.

Images