JP2012119780A - Imaging device, imaging method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highlight portion with an appropriate gray scale, when an irradiation portion by an LED light source or the LED light source itself is present in a photographic scene.SOLUTION: In an imaged image, brightness is detected on the basis of each division area obtained by dividing one screen into a plurality of screens, and a D range is determined based on the photometry result of the division photometry, and D range enlargement processing is performed according to the determined D range. The LED light source (white LED light source, monochrome LED light source) is detected from a through image (steps S12, S16). When the white LED light source is detected, the division areas are set in such a manner that the number of divisions of the division areas for division photometry is large, while when the monochrome LED light source is detected, the number of divisions is still larger as compared to the case of the white LED light source (steps S14, S20, S22). By this, it is configured that the size of the individual division area is set to fit to an LED light source having intense directivity, so that the division photometry value is not affected by another light source.

Description

  The present invention relates to an imaging apparatus, an imaging method, and a program, and more particularly to an imaging apparatus, an imaging method, and a program suitable for imaging a scene having an LED light source.

  In recent years, the number of LEDs that use LEDs (light emitting diodes) as an illumination device has increased, but LED illumination has characteristics different from those of conventional fluorescent lamps and tungsten light bulbs. Since LED illumination has strong directivity, the LED irradiation part may be overexposed. Further, in the whiteout portion of the image, the color may be rotated (the hue is shifted in the peripheral portion of the saturated region).

  In Patent Document 1, one of four types of light sources of sunlight, a light bulb, a fluorescent lamp, and LED illumination is estimated from the spectral energy distribution of the light source, and image processing is performed based on the estimated type of the light source. There is a description for obtaining a white balance gain or the like as a parameter.

  Patent Document 2 describes a digital camera including a strobe device using LEDs as a strobe light source.

  On the other hand, Patent Document 3 detects the brightness of a subject, determines whether to perform dynamic range expansion processing based on the detected brightness, and determines that dynamic range expansion processing is to be performed. In addition, the appropriate exposure value is corrected so that the exposure is underexposed by the predetermined exposure correction value, and the tone of the image signal captured according to the gamma curve corresponding to the exposure correction value (dynamic range expansion processing technology) Is described.

JP 2007-306325 A JP 2004-228723 A JP 2010-11115 A

  Patent Document 1 describes a technique for estimating an LED light source, but does not perform processing or the like peculiar to an LED light source having strong directivity.

  The invention described in Patent Document 2 is a digital camera using an LED as a strobe light source, and a scene in which highly directional LED illumination is applied to only a part of the photographing range is not assumed.

  On the other hand, Patent Document 3 discloses a technique related to a dynamic range expansion process, but does not describe an LED light source, and does not disclose a technique related to a dynamic range expansion process unique to the LED light source.

  The present invention has been made in view of such circumstances, and when there is an irradiation portion by an LED light source or the LED light source itself in a shooting scene, whiteout of the portion is prevented or suppressed, or a highlight portion is formed. An object of the present invention is to provide an imaging apparatus, an imaging method, and a program capable of giving an appropriate gradation and capable of clearly reproducing the color of a monochromatic LED light source.

  In order to achieve the object, an imaging apparatus according to a first aspect of the present invention includes an imaging unit that captures an image of a subject and acquires an image signal, a light source detection unit that detects an LED light source, and a division obtained by dividing one screen into a plurality of divisions. A divided area setting means for setting an area, wherein when the LED light source is detected by the light source detecting means, a divided area setting means for setting a divided area having a larger number of divisions than when no LED light source is detected; For each divided area set by the divided area setting means, divided photometry means for integrating the image signals acquired by the imaging means to detect the brightness of each of the divided areas, and divided photometry by the divided photometry means And a control means for controlling the dynamic range of the captured image based on the photometric result.

  According to the first aspect of the present invention, when the LED light source is detected, the number of divided areas to be divided and metered is increased as compared to the case where the LED light source is not detected (that is, each divided area is reduced). Since the divided area is set, the size of the divided area can be adjusted to the irradiation range by the LED light source having strong directivity, and the influence of other light sources on the divided photometric value in the irradiation area (divided area) of the LED light source is In other words, the brightness of the portion irradiated by the LED light source can be determined appropriately.

  The portion illuminated by the LED light source has high brightness, and if it falls outside the preset dynamic range, it will be overexposed, but by appropriately determining the brightness of the portion illuminated by the LED light source, the portion illuminated by the LED light source Dynamic range expansion processing can be performed so as not to cause whiteout.

  2. The imaging apparatus according to claim 1, wherein the light source detection unit includes a determination unit that determines whether the detected LED light source is a white LED light source or a monochromatic LED light source. The area setting means sets a divided area having a larger number of divisions when it is determined as a white LED light source when it is determined as a monochromatic LED light source by the determining means.

  In the case of a monochromatic LED light source, there is a high possibility that it will be photographed as a subject such as an electric signboard or illumination. Therefore, the divided area is made finer than the white LED light source used as illumination, and the brightness of the monochromatic LED light source is increased. It enables accurate photometry.

  As shown in claim 3, in the imaging device according to claim 1 or 2, the light source detection means has a determination means for determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, When the determination unit determines that the light source is a single color LED light source, the color correction processing unit is used to identify the color of the single color LED light source and correct the color corresponding to the region corresponding to the single color LED light source. It is characterized by that.

  Even if the dynamic range expansion processing is performed, the monochromatic LED light source becomes a subject, and the light emitting portion is whitish and becomes whitish. Therefore, the color of the single color LED light source is specified, and the area corresponding to the single color LED light source is color-corrected so as to become the specified color, thereby clearing the area corresponding to the single color LED light source (color reproducibility). (Well) can be imaged.

  An imaging apparatus according to a fourth aspect of the present invention includes an imaging unit that captures an image of a subject and acquires an image signal, a light source detection unit that detects an LED light source, and gradation conversion that performs gradation conversion of the image signal acquired by the imaging unit. And a gradation conversion means for softening or increasing the gradation conversion characteristics in the vicinity of the highlight when the LED light source is detected by the light source detection means.

  According to the invention of claim 4, when the LED light source is detected, the gradation conversion characteristic near the highlight is softened or hardened compared to the gradation conversion characteristic of a normal scene not including the LED light source. A large number of gradations are assigned to the vicinity of the highlight, or the color around the highlight is reduced.

  5. The imaging apparatus according to claim 4, wherein the light source detection unit includes a determination unit that determines whether the detected LED light source is a white LED light source or a monochromatic LED light source. The tone conversion means softens the tone conversion characteristics in the vicinity of the highlight of the acquired image signal and assigns many gradations in the vicinity of the highlight when it is determined as the white LED light source by the determination means. It is a feature.

  As shown in claim 6, in the imaging device according to claim 4 or 5, the light source detection means includes a determination means for determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, If the gradation conversion means is determined to be a single color LED light source by the determination means, the gradation conversion characteristic near the highlight of the acquired image signal is intensified, and the determination means determines that it is a single color LED light source. The color of the single color LED light source is specified, and the color of the color region different from the color of the specified single color LED light source in the region corresponding to the single color LED light source is interpolated with the peripheral color thereof It is characterized by having an interpolation means.

  According to the invention of claim 6, the gradation conversion characteristic near the highlight is hardened, so that the area corresponding to the single-color LED light source having high brightness is actively whitened, and the area of the whitened area is highlighted. The color is interpolated with the peripheral color (the color corresponding to the color of the single-color LED light source) so that the single-color LED light source can be imaged clearly.

  The imaging apparatus according to any one of claims 1 to 6, wherein the light source detection unit is a flicker having a predetermined frequency based on an image signal continuously acquired from the imaging unit. And a means for detecting a flashing luminance difference in a region where the flicker is detected, wherein the flicker at the predetermined frequency is detected and the flashing luminance difference exceeds a predetermined threshold value. The LED light source is detected based on whether or not. The LED light source is characterized in that the luminance changes at a predetermined frequency (50 Hz or 60 Hz) by a commercial AC power supply, and in particular, the luminance difference of blinking is larger than that of a fluorescent lamp. Therefore, the LED light source is detected based on the detection of flicker having a predetermined frequency and the luminance difference between flickering flickers.

  The imaging apparatus according to any one of claims 1 to 7, wherein the imaging unit includes a color imaging device having a color filter including a color filter having sensitivity at least in the vicinity of 480 nm. The light source detection means calculates a ratio between an integrated value of the color signal corresponding to a color filter having a sensitivity near 480 nm and an integrated value of other color signals among the color signals obtained from the color image sensor. And a white LED light source is detected based on whether the calculated ratio exceeds a predetermined threshold value.

  The white LED light source has spectral characteristics in which the intensity near 480 nm is extremely small. Therefore, of the color signals obtained from the color image sensor, the ratio between the integrated value of the color signal corresponding to the color filter having a sensitivity near 480 nm and the integrated value of other color signals (for example, the blue color signal). When the ratio exceeds a predetermined threshold, the white LED light source is discriminated.

  According to a ninth aspect of the present invention, there is provided an imaging method in which a subject is continuously imaged by an imaging unit, a continuous image signal is acquired, an LED light source is detected based on the acquired image signal, and a plurality of screens are provided. A step of setting a divided region formed by dividing a divided region having a larger number of divisions when an LED light source is detected than when no LED light source is detected, and the set divided region For each step, there is a step of integrating the image signals to detect the brightness of a plurality of divided regions, a step of determining a dynamic range based on the divided photometric results, and an instruction input for main imaging , Causing the image pickup means to perform main image pickup, and controlling the dynamic range of the main image picked up so as to be the determined dynamic range; It is characterized in that it comprises a.

  The imaging method according to claim 9, further comprising the step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, and the LED light source is determined to be a monochromatic LED light source. Then, a feature is that a divided region having a larger number of divisions is set as compared with a case where the white LED light source is determined.

  The imaging method according to claim 9 or 10, wherein the step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, and the LED light source is determined to be a monochromatic LED light source. Then, the method further includes the step of specifying the color of the single-color LED light source and the step of performing color correction so that the region corresponding to the determined single-color LED light source becomes the specified color.

  An imaging method according to a twelfth aspect of the present invention includes a step of imaging a subject by an imaging means to acquire an image signal, a step of detecting an LED light source based on the acquired image signal, and gradation conversion of the acquired image signal And a step of softening or hardening a gradation conversion characteristic near a highlight when the LED light source is detected.

  In the imaging method according to claim 12, including the step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, and performing the gradation conversion, When it is determined that the light source is a white LED light source, the gradation conversion characteristic in the vicinity of the highlight of the acquired image signal is softened, and many gradations are assigned in the vicinity of the highlight.

  14. The imaging method according to claim 12 or 13, wherein the gradation conversion includes the step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source. , When determined as the monochromatic LED light source, the tone conversion characteristics near the highlight of the acquired image signal are hardened, the color of the monochromatic LED light source is specified, and the region corresponding to the monochromatic LED light source The method includes a step of interpolating the color of a region different from the color of the specified single-color LED light source with the color of the peripheral portion thereof.

  A program according to a fifteenth aspect is characterized by realizing the imaging method according to any one of the ninth to fourteenth aspects.

  According to the present invention, when an LED light source is detected, an appropriate number of divided areas are determined and divided photometry is performed, so that divided photometry in an irradiation area (divided area) of an LED light source with strong directivity is performed. Thus, the dynamic range expansion process can be performed so that the portion irradiated by the LED light source does not blow out white. In addition, when an LED light source is detected, the gradation conversion characteristics near the highlight are softened or hardened compared to the gradation conversion characteristics of a normal scene that does not include the LED light source. Many gradations can be assigned or the color around the highlight can be reduced.

1 is a block diagram showing a first embodiment of an imaging apparatus according to the present invention. The figure which shows the structural example of the image pick-up element of the imaging device which concerns on this invention The figure which shows the color filter arrangement | sequence of the image of A surface read from an image pick-up element, and the image of B surface The graph which shows the signal level of the image data after the composition combined according to each D range The graph which shows the signal level of the image data after carrying out the gradation conversion further about the image data of six D ranges The flowchart which shows the imaging method by the imaging device shown in FIG. Graph showing spectral distribution of white LED The block diagram which shows 2nd Embodiment of the imaging device which concerns on this invention The flowchart which shows the imaging method by the imaging device shown in FIG. The block diagram which shows 3rd Embodiment of the imaging device which concerns on this invention Graph showing input / output characteristics of three types of gradation conversion LUTs with different gradation conversions in the highlight portion The flowchart which shows the imaging method by the imaging device shown in FIG.

  Embodiments of an imaging apparatus, an imaging method, and a program according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
<Imaging device>
FIG. 1 is a block diagram showing a first embodiment of an imaging apparatus according to the present invention.

  As shown in FIG. 1, the imaging apparatus 1 mainly includes an imaging unit 10, a central processing unit (CPU) 20, an operation unit 30, a light source determination unit 32, a D range control unit 34, a display unit (LCD) 46, and the like. Digital camera.

  The imaging unit 10 includes an optical unit 11, an imaging element 12 (hereinafter referred to as “CCD”) such as a CCD image sensor and a C-MOS image sensor, an analog signal processing unit 13, an A / D conversion unit 14, and a digital The signal processing unit 15 includes a unit driving unit 16 and a CCD driving unit 17 that drive the optical unit 11 and the CCD 12, respectively.

  The optical unit 11 includes a photographing lens, a diaphragm, a mechanical shutter, and the like, and the photographing lens (focus lens), the diaphragm, and the mechanical shutter are driven and controlled via a unit driving unit 16 according to a command from the CPU 20.

  As shown in FIG. 2, the CCD 12 is a two-dimensional color image sensor in which a large number of light receiving elements (photodiodes) are arranged in the horizontal direction (row direction) and the vertical direction (column direction) with a constant arrangement period.

  The configuration shown in FIG. 2 is a pixel array called “super CCD honeycomb EXR” developed by the present applicant, and the center points of the geometric shapes of the light receiving elements are alternately arranged in the row direction and the column direction. They are arranged with a shift of half the pixel pitch (1/2 pitch).

  Each light receiving element has an octagonal light receiving surface, and red (R), green (G), and blue (B) primary color filters are arranged corresponding to each light receiving element. As shown in FIG. 2, a row of RGRG... Is arranged in the next stage of the row of rgrg... In the horizontal direction, a line of gbgb... Is arranged in the next stage, and a line of GBGB.

  Further, an image obtained from the light receiving element group represented by uppercase RGB (A surface image) and an image obtained from the light receiving element group represented by lowercase rgb (B surface image) drive the CCD 12. It is possible to read out simultaneously by the driving sequence to be performed and to read out separately.

  That is, by applying a readout pulse to the readout electrode V1 connected to the light receiving element group of the image on the B surface of the CCD 12, the charge accumulated in the light receiving element group on the B surface can be read out to the vertical transfer path. Similarly, the charge accumulated in the light receiving element group on the A surface is read out to the vertical transfer path by applying a read pulse to the read electrode V3 connected to the light receiving element group on the A surface image of the image CCD 12. Can do. Furthermore, by simultaneously applying a read pulse to the read electrodes V1 and V3, the charges accumulated in the light receiving element groups on the B surface and the A surface can be read out to the vertical transfer paths, respectively.

  A vertical transfer path (VCCD) is formed on the right side of the light receiving element group on the A surface and on the right side of the light receiving element group on the B surface. The vertical transfer path meanders in a zigzag manner and extends in the vertical direction while avoiding the light receiving elements close to each column of the light receiving elements. The charges read on the vertical transfer path by the read pulse are transferred along the vertical transfer path by the four-phase drive pulses (φ1, φ2, φ3, φ4) applied from the CCD drive unit 17 to the electrodes V1 to V4. . Further, the CCD 12 has a so-called electronic shutter function that can sweep out charges accumulated by a shutter gate pulse applied from the CCD drive unit 17 and thereby control charge accumulation time (shutter speed). In particular, the shutter speed can be individually controlled for the light receiving element group on the A surface and the light receiving element group on the B surface.

  At the lower end of the vertical transfer path (the most downstream side of the vertical transfer path), a horizontal transfer path (HCCD) for transferring the charges transferred from the vertical transfer path in the horizontal direction is provided.

  The horizontal transfer path is composed of a transfer CCD of two-phase or four-phase drive, and a voltage signal (CCD output) corresponding to the electric charge accumulated in each light receiving element from the output unit connected to the last stage of the horizontal transfer path. Signal) is output.

  FIGS. 3A and 3B show two images, an A-side image and a B-side image, read from the CCD 12, respectively.

  As is clear from FIGS. 3A and 3B, the A-side image and the B-side image have the same color filter array (Bayer array).

  Further, the CCD output when simultaneously reading out the image on the A side and the image on the B side from the CCD 12 is the output of the line GgBbGgBb... In which the two rows GBGB... And gbgb. And the output of the line GgRrGgRr... In which two lines of the lines grgr... Are integrated are output alternately.

  Note that the light receiving element group represented by uppercase RGB constituting the image of the A side and the light receiving element group represented by lowercase rgb constituting the image of the B surface are distinguished by uppercase and lowercase letters for convenience. However, the A-side image and the B-side image when the exposure time is the same and are read simultaneously can be regarded as the same image.

  This CCD 12 is provided with a cyan (C) color filter in place of a part of G in the GBGB... Line, and in the same way, in place of a part of g in the gbgb. The color filter (c) is arranged. The CCD output of the pixels in which the cyan (C) and (c) color filters are arranged is used to detect a white light emitting diode (white LED) light source, as will be described later.

  Returning to FIG. 1, the voltage signal output from the CCD 12 is subjected to analog processing such as correlated double sampling and amplification by the analog signal processing unit 13, and then converted into A / R as R, G, and B signals for each pixel. It is added to the D converter 14. The A / D converter 14 converts analog R, G, and B signals that are sequentially added to digital R, G, and B signals, respectively. These digital R, G, and B signals are output to the digital signal processing unit 15.

  The digital signal processing unit 15 includes a white balance correction circuit, a gamma correction circuit, and a synchronization circuit (a processing circuit that interpolates a spatial shift of the color signal associated with the color filter array of the single CCD and converts the color signal into a simultaneous type. ), Luminance / color difference signal generation circuit, contour correction circuit, color correction circuit, etc., and in accordance with a command from the CPU 20, required signal processing is performed on the digital R, G, B signals input from the A / D converter 14. Thus, image data (YUV data) composed of luminance data (Y data) and color difference data (Cr, Cb data) is generated. The image data generated by the digital signal processing unit 15 is output to the compression / decompression processing circuit 42.

  The CPU 20 is a part that performs overall control of the entire apparatus in accordance with an operation input from the operation unit 30 and a predetermined program, and is a calculation unit that performs various calculations such as automatic exposure (AE) calculation, auto white balance (AWB) gain calculation, and the like. Function as.

  A random access memory (RAM) 38 and a read only memory (ROM) 40 are connected to the CPU 20 via a bus 48 and a memory interface 36. The RAM 38 is used as a program development area and a calculation work area for the CPU 20, and is also used as a temporary storage area for image data. The ROM 40 stores programs executed by the CPU 20, various data necessary for control, various constants / information related to the imaging operation, and the like.

  The operation unit 30 includes a shutter button, a mode selection switch for selecting a shooting mode and a playback mode, a menu button for displaying a menu screen on the LCD 46, a multi-function cross key for selecting a desired item from the menu screen, and the like. It is. An output signal from the operation unit 30 is input to the CPU 20 via the bus 48, and the CPU 20 performs appropriate processing such as shooting and reproduction based on the input signal from the operation unit 30.

  The imaging apparatus 1 includes a flash device 24 for irradiating a subject with flash light. The flash device 24 receives power from the charging unit 22 in response to a light emission command from the CPU 20 and irradiates flash light.

  The imaging unit 10 performs an imaging operation or the like according to a command from the CPU 20, and the image data (luminance signal Y, color difference signals Cr, Cb) processed by the digital signal processing unit 15 is given to the compression / decompression processing circuit 42, where Thus, compression is performed according to a predetermined compression format (for example, JPEG method). The compressed image data is recorded in the memory card 28 via the external memory I / F 26 in the format of an image file (for example, a JPEG file).

  In addition, a through image (live view image) is displayed on the LCD 46 during imaging preparation by an image signal applied via the LCD interface 44, and a JPEG file recorded on the memory card 28 in the playback mode is read out. , The image is displayed. The compressed image data stored in the JPEG file is decompressed by the compression / decompression processing circuit 42 and output to the LCD 46.

  In this embodiment, the light source discriminating unit 32 is a part that discriminates the presence or absence of an LED light source (white LED light source, monochromatic LED light source), but other light sources (sunlight (shade, cloudy, sunny), tungsten bulb, A fluorescent lamp (daylight color, day white-white, warm white) may also be identified. The determined type of light source is used to calculate the AWB gain. The LED light source discrimination result is used to select the type of divided area (divided area obtained by dividing one screen into a plurality of areas) for performing divided photometry.

  For example, as a divided area for performing divided photometry, etc., one screen is divided into 64 (= 8 × 8), the divided number A is divided into “small”, and one screen is divided into 256 (= 16 × 16). In the case where the CPU 20 has the division area B with the division number “medium” and the division area C with the division number “large” for dividing one screen into 4096 (= 64 × 64), the CPU 20 causes the light source determination unit 32 to Is detected, a divided area B is set. If a monochromatic LED light source is detected, a divided area C is set. If no LED light source is detected, the divided area A is set.

  When the divided areas are set as described above, the CPU 20 sets the integrated values for each color signal of the R, G, and B signals and the luminance signal (or G signal) obtained from the R, G, and B signals for each divided area. Based on the integrated value, the average luminance value of each divided area is obtained, and the luminance value of each divided area (average luminance value) is multiplied by the weighting coefficient for each divided area to perform weighted averaging to obtain subject brightness (subject brightness). And an exposure value (photographing EV value) suitable for photographing is calculated. This is a weighting factor for each divided area, and differs depending on the center-weighted metering method, the average metering method, and the like.

  Further, the CPU 20 determines the dynamic range (D range) based on the luminance distribution measured for each divided region or the luminance of the divided region having the highest luminance.

  The D range control unit 34 is a part that performs D range expansion processing and the like based on the D range determined by the CPU 20. The D range control unit 34 may be provided as a part of the digital signal processing unit 15.

  Next, the D range expansion process by the D range control unit 34 will be described.

  In response to an instruction from the CPU 20, a high-sensitivity image with a narrow D range and a low-sensitivity image with a wide D range (an image darker than the high-sensitivity image) are simultaneously captured by the imaging unit 10. These high-sensitivity images and low-sensitivity images can be acquired by making the shutter speeds of the A-side light-receiving element group different from the B-side light-receiving element group as described with reference to FIGS. .

  The D range control unit 34 performs gradation conversion on each of the high sensitivity image and the low sensitivity image based on the D range determined by the CPU 20 and then adds them. For example, as shown in FIG. 4, the maximum value of the signal level of the combined image data synthesized according to the width of each D range (100%, 130%, 170%, 230%, 300%, 400%) Are matched with each other and the signal level is smoothly changed from the luminance 0 to the maximum luminance of each D range. That is, the gradation conversion between the high-sensitivity image and the low-sensitivity image is performed so that the synthesis result shown in FIG. 4 is obtained.

  When the D range is 100%, only the high sensitivity image data is used without synthesizing the high sensitivity image data and the low sensitivity image data, and gradation conversion of the high sensitivity image data is not performed. Further, here, the subject luminance giving the level at the time when the high-sensitivity image data is saturated is set to 100%. Further, the image data that has been subjected to the D-range expansion processing or the like as described above is then gamma corrected. FIG. 5 shows the signal level of the image data after the gamma correction is performed on the image data that has undergone the D range expansion processing.

  In addition, the D range expansion processing is not limited to the above-described embodiment. For example, the exposure value is corrected so that the exposure value is underexposed by a predetermined exposure correction value from the appropriate exposure value, and further compared with a normal gradation conversion curve. The D range can be expanded by performing a gamma conversion process using a gradation conversion curve in which the high luminance side is flat (the inclination is small) and the halftone is greatly raised.

<Imaging method>
FIG. 6 is a flowchart showing an imaging method by the imaging apparatus 1 shown in FIG.

  When the shooting mode is set, a shooting standby state is set, and the CPU 20 causes the imaging unit 10 to continuously capture an image of the subject at a predetermined frame rate, obtains image signals for continuous through images, and displays through images. The image is displayed on the LCD 46 (step S10). The light source determination unit 32 determines the presence or absence of an LED light source based on the image signal for the through image (step S12). The determination of the LED light source is performed as follows.

  Many LED light sources blink, and the luminance difference of blinking is larger than that of a fluorescent lamp. Since blinking depends on the frequency of the AC power supply, the frequency is 50 Hz or 60 Hz. Hereinafter, this blinking is referred to as “flicker”. In order to detect flicker, it is preferable that the frame frequency or the shutter timing is not an integral multiple of the frequency of 50 Hz or 60 Hz, and the shutter speed is sufficiently shorter than one frame period.

  One screen is divided into LED light source detection sizes (the size is arbitrary), and an average luminance is calculated for each divided region with respect to continuously acquired image signals. Then, flicker is detected from the difference value of the average luminance calculated from the image signals before and after the same divided area. Further, the maximum luminance difference of flicker is detected, and when the luminance difference exceeds a predetermined threshold (threshold for distinguishing from an incandescent lamp or a fluorescent lamp), it is detected as an LED light source. Note that incandescent lamps and fluorescent lamps do not have the luminance response in time for the voltage change of the AC power supply, but the LED has a very fast luminance response (about 10 nanoseconds) compared to other artificial light sources, so the maximum voltage The luminance responds to the minimum, and the difference value increases.

  In step S12, when the LED light source is not detected, the process proceeds to step S14. When the LED light source is detected, the process proceeds to step S16.

  In step S16, it is determined whether the LED light source detected in step S12 is a white LED light source or a monochromatic LED light source.

  Whether the light source is a white LED light source or a monochromatic LED light source is determined by the spectral characteristics of the LED light source. The white LED has a spectral distribution as shown in FIG. 7, and the spectral intensity near 480 nm is extremely low. Therefore, the ratio between the color signal corresponding to the pixel of the color filter (cyan color filter) having sensitivity near 480 nm and the color signal corresponding to the pixel of the color filter (blue color filter) having sensitivity near 450 nm is If the predetermined threshold value is exceeded, it is determined as a white LED light source.

  In step S18, the integrated value of the color signals of the pixels of the cyan color filter in the region where the LED light source is detected in step S12 in the through image, and the blue color filter at a position corresponding to the cyan color filter. In step S16, it is determined whether or not the LED light source is a white LED light source based on the ratio of the integrated values obtained in step S18.

  If it is determined in step S16 that the light source is a white LED light source, the process proceeds to step S20. If it is determined that the light source is not a white LED light source (monochromatic LED light source), the process proceeds to step S22.

  In steps S14, S20, and S22, divided areas for performing divided photometry are set. That is, in step S14, the 8 × 8 division number “small” division region A is set as described above, and in step S20, the 16 × 16 division number “medium” division region B is set, and step S22. Then, a division area B having a division number “large” of 64 × 64 is set.

  As the number of divisions increases, one divided region becomes smaller. Since the LED light source has strong directivity, if the divided area is large, it is averaged at the time of divided photometry, and the luminance of the area corresponding to the LED light source cannot be accurately detected. On the other hand, by setting the divided areas B and C having a large number of divisions, the luminance by the LED light source can be divided and measured with high accuracy.

  Also, the reason why the number of divisions C of the monochromatic LED light source is larger than that of the white LED light source is that the white LED light source is often used as an illumination light source, whereas the monochromatic LED light source is This is because it is often a subject that is directly imaged, such as an electric signboard or illumination.

  When the divided areas are set as described above, the CPU 20 performs divided photometry based on the set divided areas, and based on the luminance distribution for each divided area or the luminance of the divided area having the highest luminance. The D range is determined (step S24). For example, as shown in FIG. 4, any one of 100%, 130%, 170%, 230%, 300%, and 400% is set as the D range.

  In a divided area corresponding to an LED light source (white LED light source, monochromatic LED light source), a divided photometric value with high luminance may be obtained. In this case, the divided range corresponding to the LED light source can be obtained by expanding the D range. The image of the region can be prevented from being saturated or difficult to be saturated.

  Thereafter, when there is an instruction input for main imaging (S2 signal corresponding to full-pressing of the two-stage shutter) (step S26), the imaging unit 10 performs the main imaging and acquires image data by the main imaging (step S28). .

  The D range control unit 34 performs D range expansion processing corresponding to the D range set in step S24 on the image data acquired by the main imaging (step S30). If the D range is set to 100%, the process for expanding the D range is not performed.

  The digital signal processing unit 15 performs image processing such as white balance correction, gamma correction, synchronization processing, YC processing, contour correction circuit, and color correction on the image data after the D range expansion processing (step S32). . Note that some image processing (for example, white balance correction) may be performed on image data before D range expansion processing.

  A final image is generated by the above processing, and the final image is compressed by the compression / decompression processing circuit 42 and then recorded on the memory card 28 via the external memory I / F 26, and the photographing process is completed (step S34). ).

  The determination of the divided area is performed based on the presence or absence of the LED light source detected based on the through image, but the divided photometry is based on the image signal captured when the S1 signal corresponding to half-pressing of the two-stage shutter is input. Do it.

[Second Embodiment]
<Imaging device>
FIG. 8 is a block diagram showing a second embodiment of the imaging apparatus according to the present invention.

  The imaging device 2 shown in FIG. 8 is different from the imaging device 1 of the first embodiment shown in FIG. 1 in that a color correction unit 50 is mainly added. In addition, the same code | symbol is attached | subjected to the part which is common in the imaging device 1 shown in FIG. 1, and the description is abbreviate | omitted.

  The imaging device 2 of the second embodiment performs the determination of the D range, the D range expansion processing, and the like in the same manner as the imaging device 1 of the first embodiment, and neatly reproduces the area corresponding to the monochromatic LED light source. A color correction unit 50 is added.

  That is, even if the D range expansion processing is performed, the monochromatic LED light source becomes a subject, and the light emitting portion is whitened and becomes whitish.

  When the light source determination unit 32 detects a single color LED light source, the color correction unit 50 specifies the color of the single color LED light source. As for the color of the monochromatic LED light source, when an area corresponding to the monochromatic LED light source is detected, R, G, and B color signals for each area (corresponding area of the divided areas C having the large number of divisions). Specify the color from Thereafter, an area corresponding to the monochromatic LED light source is identified from the actually captured image.

  When specifying the region corresponding to the single color LED light source from the captured image, the region having high brightness based on the position information of the divided region corresponding to the single color LED light source and the color of the specified single color LED light source (A region that is whitened and becomes whitish) and a peripheral region (a region having the same color as the color of the specified single-color LED light source) are specified in units of pixels.

  The color correction unit 50 performs correction for adding a color of a peripheral region to a whitish region among regions corresponding to the specified single color LED light source. In this way, the area corresponding to the single color LED light source is color-corrected so that the specified color is obtained, so that the area corresponding to the single color LED light source can be clearly reproduced.

<Imaging method>
FIG. 9 is a flowchart showing an imaging method by the imaging apparatus 2 shown in FIG. In addition, the same step number is attached | subjected to the part which is common in the flowchart corresponding to the imaging device 1 of 1st Embodiment shown in FIG. 6, The detailed description is abbreviate | omitted.

  The flowchart of FIG. 9 is different from the flowchart shown in FIG. 6 in that steps S40, S42, and S44 for performing color correction processing by the color correction unit 50 are added.

  In step S40, when a single color LED light source is detected, the position of the divided area of the single color LED light source and the color of the divided area are specified. As the divided area when the monochromatic LED light source is detected, the divided area C having the large number of divisions (one divided area having a small size) is set, and therefore R of the divided area where the monochromatic LED light source is detected. The color of the divided area can be specified from the integrated values of the color signals of G, B, and B.

  Step S42 is an image that is actually captured based on the image that is actually captured and the position and color information corresponding to the monochrome LED light source that is identified in Step S40 during the actual imaging when the monochrome LED light source is detected. A whitish area having high brightness from the middle and a peripheral colored area (an area having the same color as the color of the specified single-color LED light source) are specified in units of pixels.

  In step S44, the brightness data (Y data) and color difference data (Cr, Cb data) of the whitish area that is high brightness by the single color LED light source specified in step S42, and the Y data of the color of the surrounding area are obtained. Correction is made so as to replace with Cr and Cb data.

  In this way, the area corresponding to the single color LED light source is color-corrected so that the specified color is obtained, so that the area corresponding to the single color LED light source can be clearly reproduced.

[Third Embodiment]
<Imaging device>
FIG. 10 is a block diagram showing a third embodiment of the imaging apparatus according to the present invention.

  Compared with the imaging apparatus 1 of the first embodiment shown in FIG. 1, the imaging apparatus 3 shown in FIG. 10 mainly includes a gradation control unit 60 instead of the D range control unit 34 of the imaging apparatus 1. And a color interpolation unit 62 is added. In addition, the same code | symbol is attached | subjected to the part which is common in the imaging device 1 shown in FIG. 1, and the description is abbreviate | omitted.

  When the LED light source (white LED light source, single color LED light source) is detected by the light source determination unit 32, the imaging device 3 of the third embodiment changes the gradation conversion characteristics instead of performing D range expansion processing or the like. Like to do.

  That is, the gradation control unit 60 has a look-up table (LUT) that performs predetermined gradation conversion on the input R, G, and B color signals according to the level of the input signal and outputs the converted signals. As shown in FIG. 11, there are three types of gradation conversion LUTs with different gradation conversions in the highlight portion.

  In FIG. 11, the LUT indicating the gradation conversion characteristic indicated by the solid line corresponds to a normal scene in which the LED light source is not detected, and the LUT indicating the gradation conversion characteristic indicated by the dotted line is the white LED light source. The LUT corresponding to the detected scene and indicating the gradation conversion characteristic indicated by the alternate long and short dash line corresponds to the scene in which the monochromatic LED light source is detected.

  That is, the gradation control unit 60 selectively uses each of the above LUTs, and when a white LED light source is detected, the gradation conversion characteristic near the highlight is softer than the gradation conversion characteristic of the normal scene. On the other hand, when a monochromatic LED light source is detected, the tone control is performed so that the tone conversion characteristic near the highlight is harder than the tone conversion characteristic of a normal scene. .

  As a result, in a scene in which a white LED light source is detected, a large number of gradations are assigned to the vicinity of the highlight, and whiteout of an image in the vicinity of the highlight (image of the irradiation area of the white LED light) is reduced. In the scene in which the LED light source is detected, an image in the vicinity of the highlight (an image in which the monochromatic LED light source is a subject) is intentionally blown out, and color rotation is reduced.

  For example, when the monochromatic LED light source is a red LED light source, the R signal is saturated first, then the G signal is saturated, and finally the B signal is saturated. Therefore, in the central portion of the red LED light source, the R, G, and B signals are saturated and become whitish, and a yellow edge in which only the R and G signals are saturated is generated (color rotation occurs). A red portion in which the R signal is saturated is generated around it. In addition, if the color of a monochromatic LED light source is specified, the color which turns around can be specified.

  When a single color LED light source is detected, the color interpolation unit 62 specifies the color of the single color LED light source, and determines the color of the edge where the color rotation occurs as the color of the periphery (corresponding to the color of the single color LED light source). Interpolate with.

  As a result, it is possible to remove the influence of color rotation that occurs in the image corresponding to the single color LED light source.

  The gradation control unit 60 may be incorporated in the gamma correction circuit in the digital signal processing unit 15.

<Imaging method>
FIG. 12 is a flowchart showing an imaging method by the imaging apparatus 3 shown in FIG. In addition, the same step number is attached | subjected to the part which is common in the flowchart corresponding to the imaging device 1 of 1st Embodiment shown in FIG. 6, The detailed description is abbreviate | omitted.

  In FIG. 12, when the LED light source is not detected, the normal gradation conversion characteristic is set as the gradation conversion characteristic (step S50), and when the white LED light source is detected, the gradation conversion near the highlight is performed. A gradation conversion characteristic in which the characteristics are softened is set (step S52), and if a monochromatic LED light source is detected, a gradation conversion characteristic in which the gradation conversion characteristics in the vicinity of the highlight are hardened is set (step S52). S54).

  In step S32 ′, various types of signal processing are performed on the actually captured image data, but gradation conversion is performed using the LUT corresponding to the gradation conversion characteristics set in steps S50, S52, or S54. . As a result, in the scene in which the white LED light source is detected, the vicinity of the highlight is softened, and by assigning many gradations, whiteout is reduced, and in the scene in which the monochromatic LED light source is detected, the vicinity of the highlight is Color tone is reduced by making the tone high and intentionally whitening.

  On the other hand, step S56 specifies a color for each position of the monochromatic LED light source when a monochromatic LED light source is detected.

  Step S58 is an image that has been actually captured based on the image that has been actually captured and the position and color information corresponding to the monochrome LED light source that has been identified in Step S40 during the actual imaging when the monochrome LED light source is detected. A whitish area having high brightness from the middle and an area with surrounding colors (an area of the same color as the color of the specified single-color LED light source, an area around the color) are identified.

  In step S60, among the image data processed in step S32 ', color interpolation processing is further performed by the color interpolation unit 62 on the image data when the monochromatic LED light source is detected. That is, in step S60, the color of the region around the color specified in step S58 is interpolated (replaced) with the color of the peripheral region (the same color as the color of the specified single-color LED light source).

  As a result, it is possible to remove the influence of color rotation that occurs in the image corresponding to the single color LED light source.

[Others]
In the first embodiment, when an LED light source is detected, it is further determined whether the LED light source is a white LED light source or a monochromatic LED light source, and different divided areas are set for each. However, regardless of the type of the LED light source, when the LED light source is detected, a divided region having a larger number of divisions may be set as compared with the case where the LED light source is not detected.

  Further, the D range determination method based on the divided photometry result in the set divided area and the D range expansion process using the determined D range are not limited to those of the first embodiment.

  Further, in the third embodiment, when a color LED light source is detected, the highlight area is hardened and color correction (color interpolation) is performed. However, the present invention is not limited to this, and color correction is not performed. May be. Even in this case, there is an effect of reducing the color rotation generated in the image corresponding to the monochromatic LED light source.

  Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1, 2, 3 ... Image pick-up device, 10 ... Image pick-up part, 11 ... Optical unit, 12 ... Image pick-up element (CCD), 15 ... Digital signal processing part, 20 ... Central processing unit (CPU), 30 ... Operation part, 32 ... Light source discriminating unit 34 ... D range control unit 50 ... color correction unit 60 ... tone control unit 62 ... color interpolation unit

Claims (15)

Imaging means for imaging a subject and obtaining an image signal;
Light source detection means for detecting an LED light source;
A divided area setting means for setting a divided area obtained by dividing one screen into a plurality of divided areas having a larger number of divisions when an LED light source is detected by the light source detecting means than when no LED light source is detected. Divided region setting means for setting
Divided photometry means for integrating the image signals acquired by the imaging means for each divided area set by the divided area setting means and detecting the brightness of each of the divided areas;
Control means for controlling the dynamic range of the captured image based on the photometric result obtained by the division photometry by the division photometry means;
An imaging apparatus comprising: The light source detection means includes a determination means for determining whether the detected LED light source is a white LED light source or a monochromatic LED light source;
The division area setting unit sets a division area having a larger number of divisions than the case where it is determined as a white LED light source when the determination unit determines that the LED light source is a monochromatic LED light source. Imaging device. The light source detection means includes a determination means for determining whether the detected LED light source is a white LED light source or a monochromatic LED light source;
When the determination unit determines that the light source is a single color LED light source, the color correction processing unit is used to identify the color of the single color LED light source and correct the color corresponding to the region corresponding to the single color LED light source. The imaging apparatus according to claim 1 or 2, wherein Imaging means for imaging a subject and obtaining an image signal;
Light source detection means for detecting an LED light source;
A gradation conversion unit that performs gradation conversion of an image signal acquired by the imaging unit, and when the LED light source is detected by the light source detection unit, the gradation conversion characteristic near the highlight is softened or hardened. Gradation conversion means;
An imaging apparatus comprising: The light source detection means includes a determination means for determining whether the detected LED light source is a white LED light source or a monochromatic LED light source;
The gradation conversion means softens the gradation conversion characteristics in the vicinity of the highlight of the acquired image signal and assigns many gradations in the vicinity of the highlight when the determination means determines that the light source is a white LED light source. The imaging apparatus according to claim 4. The light source detection means includes a determination means for determining whether the detected LED light source is a white LED light source or a monochromatic LED light source;
If the gradation converting means is determined to be a monochromatic LED light source by the determining means, the gradation converting characteristics in the vicinity of the highlight of the acquired image signal are hardened,
If it is determined that the single-color LED light source is determined by the determining means, the color of the single-color LED light source is specified, and the color of an area different from the color of the specified single-color LED light source in the area corresponding to the single-color LED light source The imaging apparatus according to claim 4, further comprising color interpolation means for interpolating the image with the color of the peripheral portion thereof.   The light source detection means includes means for detecting a flicker having a predetermined frequency based on image signals continuously acquired from the imaging means, and means for detecting a luminance difference of blinking in an area where the flicker is detected. The LED light source is detected based on whether or not the flicker of the predetermined frequency is detected and whether the luminance difference of the blinking exceeds a predetermined threshold value. The imaging device according to item. The imaging means has a color imaging device having a color filter including a color filter having sensitivity at least in the vicinity of 480 nm,
The light source detecting means is a means for calculating a ratio between an integrated value of color signals corresponding to a color filter having a sensitivity near 480 nm and an integrated value of other color signals among color signals obtained from the color image sensor. 8. The imaging apparatus according to claim 1, wherein a white LED light source is detected based on whether or not the calculated ratio exceeds a predetermined threshold value. 9. Capturing a continuous image signal by continuously capturing an image of a subject by an imaging unit;
Detecting an LED light source based on the acquired image signal;
A step of setting a divided region formed by dividing one screen into a plurality of regions, and when a LED light source is detected, a step of setting a divided region having a larger number of divisions compared to a case where the LED light source is not detected;
Detecting the brightness of each of the plurality of divided areas by integrating the image signals for each of the set divided areas;
Determining a dynamic range based on the divided photometric results;
When there is an instruction input for actual imaging, the imaging means performs actual imaging and controls the dynamic range of the actual captured image to be the determined dynamic range;
An imaging method comprising:   The step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source. When the LED light source is determined to be a monochromatic LED light source, the number of divisions is larger than that in the case where the detected LED light source is determined to be a white LED light source. The imaging method according to claim 9, wherein a large number of divided areas are set.   The step of determining whether the detected LED light source is a white LED light source or a single color LED light source, and the step of specifying the color of the single color LED light source when the LED light source is determined to be a single color LED light source, are determined. The imaging method according to claim 9, further comprising a step of performing color correction so that an area corresponding to a single color LED light source has the specified color. Capturing an image of a subject with an imaging means and obtaining an image signal;
Detecting an LED light source based on the acquired image signal;
Gradation conversion of the acquired image signal, wherein when the LED light source is detected, the gradation conversion characteristics near the highlight are softened or hardened; and
An imaging method comprising:   The step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, and the step of performing the gradation conversion is a highlight of the acquired image signal when determined as the white LED light source. 13. The imaging method according to claim 12, wherein a gradation conversion characteristic in the vicinity is softened, and a large number of gradations are assigned in the vicinity of the highlight. The step of determining whether the detected LED light source is a white LED light source or a monochromatic LED light source, and the step of performing the gradation conversion is a highlight of the acquired image signal when determined as the monochromatic LED light source. Increase the gradation conversion characteristics in the vicinity,
Specifying the color of the single-color LED light source, and interpolating the color of the region different from the color of the specified single-color LED light source in the region corresponding to the single-color LED light source with the color of the peripheral portion thereof The imaging method according to claim 12 or 13, characterized in that:   The program which implement | achieves the imaging method of any one of Claim 9 to 14.

Images