JP4029206B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus such as an electronic camera that images a subject and records electronic image data.
[0002]
[Prior art]
The subject image that has passed through the photographic lens is captured by a CCD or the like, and an image processing device that outputs image data and an image processing such as white balance adjustment and γ correction are performed by adjusting an amplification gain for the image data output from the image capturing device. An electronic camera including an image processing circuit is known. The image processing circuit calculates parameters such as R gain and B gain for white balance adjustment, or gradation curve for γ correction based on image data output from the imaging device, using a predetermined algorithm. Is done.
[0003]
[Problems to be solved by the invention]
In the conventional electronic camera, the white balance adjustment coefficient is calculated so that the average value of the color information of the captured main subject and the background becomes an achromatic color such as white or gray, and the calculated adjustment coefficient is used for image data. White balance adjustment is performed. Generally, when the light source that illuminates the subject changes, the color of the subject appears to change. For example, it becomes a reddish color under sunlight in the morning and evening, and a greenish color under fluorescent light. When conventional white balance adjustment is performed in such a case, there is a possibility that so-called color feria may be generated by correction with complementary colors for red and green, respectively. As a result, white balance adjustment failure tends to occur.
[0004]
The present invention provides an imaging apparatus such as an electronic camera that estimates the type of light source and performs white balance adjustment to prevent color failure.
[0005]
[Means for Solving the Problems]
The invention of claim 1 is applied to an image pickup apparatus, an image pickup means for picking up a subject image passing through a photographing lens and outputting an image pickup signal, a chromaticity detection means for detecting the chromaticity of the subject, and a chromaticity detection means. Light source estimation means for estimating the type of light source that illuminates the subject using the chromaticity detected by the above, gain calculation means for calculating gain using color temperature information corresponding to the light source estimated by the light source estimation means, A gain adjusting means for performing gain adjustment by applying a gain calculated by the gain calculating means to the imaging signal output from the imaging means; and whether the luminance for each predetermined area obtained by dividing the subject is higher than a second predetermined value A second luminance determining unit that determines whether or not the light source estimating unit uses the chromaticity detected in the region for each region when the second luminance determining unit determines that the luminance is high. Multiple The color used when the type of light source is estimated, and one type of sunlight is regarded as the light source of the subject in accordance with the number of light sources estimated in each region, and the gain calculation means uses the light source estimation means as the light source of the subject. An average of degrees is calculated, and gain is calculated using color temperature information corresponding to the calculated average value.
According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, the chromaticity detection means detects the chromaticity of the subject based on the imaging signal output from the imaging means.
According to a third aspect of the present invention, in the imaging apparatus according to the first aspect, the chromaticity detection unit includes a chromaticity detection imaging unit that images a subject and outputs a chromaticity detection imaging signal separately from the imaging unit. The chromaticity of the subject is detected based on the chromaticity detection imaging signal output from the chromaticity detection imaging means.
According to a fourth aspect of the present invention, in the imaging apparatus according to any one of the first to third aspects, the light source estimation means includes a plurality of pieces of chromaticity information given in advance corresponding to a plurality of predetermined light sources. From this, the light source corresponding to the chromaticity information substantially coincident with the chromaticity detected by the chromaticity detecting means is estimated.
The invention of claim 5 is the imaging device according to claim 4,
The plurality of predetermined light sources are sunlight at a predetermined plurality of color temperatures and a plurality of predetermined types of fluorescent lamps, and the chromaticity information is substantially achromatic under illumination by the respective sunlight and each fluorescent lamp. As shown, it is given discretely.
The invention of claim 6 is the imaging device according to any one of claims 1 to 5,
First luminance determination means for determining whether the luminance for each predetermined area obtained by dividing the object scene is higher than a first predetermined value, and the chromaticity detection means for the color of the subject for each predetermined area The light source estimating means estimates the types of a plurality of light sources using the chromaticity detected in the area for each area determined to have high brightness by the first brightness determining means, According to the estimated number of light sources, one type of light source is regarded as the light source of the subject, and the gain calculating means calculates the average of the chromaticities used when the light source estimating means regards the light source of the subject, and calculates the average value The gain is calculated using the color temperature information corresponding to.
According to a seventh aspect of the present invention, in the image pickup apparatus according to the first aspect, the gain calculating means determines a predetermined color when sunlight having any color temperature is not regarded as a light source of the subject by the light source estimating means. The gain is calculated using temperature information.
According to an eighth aspect of the present invention, in the imaging device according to any one of the first to seventh aspects, the gain calculating means includes a light source that illuminates the subject and an LUT that outputs gain using the color temperature information as an argument. It is a feature.
Claim 9 The invention of claim 1 to claim 1 8 The imaging device according to any one of the above, wherein the imaging device is an electronic camera.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
-First embodiment-
The first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a single-lens reflex electronic still camera according to an embodiment of the present invention. In FIG. 1, the electronic still camera includes a camera body 70, a finder device 80 that is attached to and detached from the camera body 70, and an interchangeable lens 90 that includes a lens 91 and a diaphragm 92 and is attached to and detached from the camera body 70. The subject light that has passed through the interchangeable lens 90 and entered the camera body 70 is guided to the finder device 80 by the quick return mirror 71 located at the position indicated by the dotted line before being released, and forms an image on the finder mat 81, and the focus detection device. An image is also formed on 36. The subject light imaged on the finder mat 81 is further guided to the eyepiece lens 83 by the pentaprism 82, and is also guided to the color sensor 86 through the prism 84 and the imaging lens 85. Is imaged. After the release, the quick return mirror 71 rotates to the position indicated by the solid line, and the subject light forms an image on the imaging device 73 for photographing via the shutter 72. The color sensor 86 is disposed at a position conjugate with the imaging device 73 with respect to the photographing lens 91.
[0007]
FIG. 2 is a circuit block diagram of the electronic still camera. The CPU 21 receives a half-press signal and a full-press signal from a half-press switch 22 and a full-press switch 23 that are linked to the release button, respectively. The focus detection device 36 detects the focus adjustment state of the photographic lens 91 according to a command from the CPU 21. The lens driving device 37 drives the lens 91 to the in-focus position so that the subject light incident on the interchangeable lens 90 forms an image on the imaging element 26 of the imaging device 73. Further, the CPU 21 drives and controls the image pickup device 26 of the image pickup device 73 by driving the timing generator 24 and the driver 25. Operation timings of the analog processing circuit 27 and the A / D conversion circuit 28 are controlled by the timing generator 24.
[0008]
When the full-push switch 23 is turned on following the half-push switch 22 being turned on, the quick return mirror 71 is rotated upward, and the subject light from the interchangeable lens 90 forms an image on the light receiving surface of the image sensor 26. Is done. The image sensor 26 is a CCD, and accumulates signal charges corresponding to the brightness of the subject image. The signal charges accumulated in the image sensor 26 are swept out by the driver 25 and input to an analog signal processing circuit 27 including an AGC circuit and a CDS circuit. The input analog image signal is subjected to analog processing such as gain control and noise removal in the analog signal processing circuit 27 and then converted into a digital signal by the A / D conversion circuit 28. The digitally converted image signal is guided to, for example, an image processing CPU 29 configured as an ASIC, and image preprocessing such as white balance adjustment, contour compensation, and gamma correction described later is performed.
[0009]
The image data that has undergone image preprocessing is further subjected to format processing (image post processing) for JPEG compression, and the image data after the format processing is temporarily stored in the buffer memory 30.
[0010]
The image data stored in the buffer memory 30 is processed into display image data by the display image creation circuit 31 and displayed as a photographing result on a viewfinder 32 such as an LCD. Further, the image data stored in the buffer memory 30 is subjected to data compression at a predetermined ratio by the JPEG method by the compression circuit 33 and recorded on a recording medium (CF card) 34 such as a flash memory.
[0011]
White balance adjustment is performed by the image processing CPU 29. Of the R, G, and B color image signals output from the A / D conversion circuit 28, the R gain and the B gain for white balance adjustment are respectively multiplied to the R color and B color image signals. The white balance adjustment R gain and B gain are determined by the white balance detection circuit 35 and stored in the memory 35D.
[0012]
The white balance detection circuit 35 includes a color sensor 86 that detects the color of the subject, an A / D conversion circuit 35B that converts an analog color signal output from the color sensor 86 into a digital color signal, and a converted digital color signal. A CPU 35C that generates a white balance adjustment coefficient based on the memory 35D and a memory 35D in which a reference lookup table (LUT) is recorded. The CPU 35C determines an R gain and a B gain for white balance adjustment based on the color signal detected by the color sensor 86, and records them in the memory 35D. In the present embodiment, the CPU 35C estimates the light source that illuminates the subject using the color signal output from the color sensor 86, and determines the white balance adjustment gain according to the estimated type of the light source. Then, the image processing CPU 29 performs white balance adjustment using the white balance adjustment gain determined by the CPU 35C.
[0013]
The color sensor 86 is, for example, a single two-dimensional imaging element having 480 pixels divided into 48 columns × 10 rows as shown in FIG. On the surface of the image sensor 86, a color filter 861 is provided in which any one of R, G, and B filters is provided corresponding to 480 pixels. When the subject light is imaged by the color sensor 86 through the color filter 861, the subject light is decomposed into an R color signal, a G color signal, and a B color signal and imaged. The color signal output from the color sensor 86 includes three adjacent pixels that output R, G, and B color signals as one pixel, for example, a color signal for 160 pixels in 16 rows x 10 rows. Is output as That is, the color sensor 86 divides the imaging surface into 160 areas and outputs a color signal.
[0014]
4 and 5 are flowcharts for explaining the flow of processing for determining the white balance adjustment gain according to the present embodiment. 4 and 5 are repeatedly performed before the electronic still camera is released. In step S <b> 11 of FIG. 4, signal charges are accumulated in the color sensor 86, and the accumulated charge signals are swept out of the color sensor 86. The swept color signal is converted into a digital color signal by the A / D conversion circuit 35B and then input to the CPU 35C. In step S12, the CPU 35C, for each of R, G, and B color signals (480 signals) for 160 pixels input from the color sensor 86, ratio of R color data to G color data for each pixel, B color data. And the ratio of the G color data are calculated, and the process proceeds to step S13.
[0015]
In step S13, the CPU 35C determines whether there is data indicating an achromatic color for the calculated 160 sets of chromaticity data (RG) / G and (BG) / G. If there is achromatic color data, the CPU 35C makes a positive determination in step S13 and proceeds to step S14. If there is no achromatic color data, the CPU 35C makes a negative determination in step S13 and proceeds to step S16. FIG. 6 is a diagram illustrating an achromatic color distribution on chromaticity coordinates. In FIG. 6, the vertical axis is (RG) / G, and the horizontal axis is (BG) / G.
[0016]
In FIG. 6, a region 1 is a region indicating the chromaticity of an achromatic subject illuminated by sunlight having a color temperature of 3000K. Regions 2 to 6 are regions indicating the chromaticities of achromatic subjects illuminated by sunlight having color temperatures of 4250K, 4520K, 5120K, 6130K, and 6620K, respectively. An area 7 is an area indicating the chromaticity of an achromatic object illuminated by a three-wavelength type color rendering white fluorescent lamp (EX-W). Regions 8 and 9 indicate the chromaticity of the achromatic object illuminated by the three-wavelength color rendering daylight fluorescent lamp (EX-N) and the three-wavelength color rendering daylight fluorescent lamp (EX-D), respectively. It is an area shown. Further, regions 10 to 12 are regions indicating the chromaticity of the achromatic object illuminated by the normal white fluorescent lamp (W), the daylight white fluorescent lamp (N), and the daylight color fluorescent lamp (D), respectively. .
[0017]
The CPU 35C determines that there is achromatic color data when the calculated chromaticity data (RG) / G and (BG) / G are included in any of the regions 1 to 12 in FIG. When it is not included in any of the areas 12, it is determined that there is no achromatic color data. In step S14 of FIG. 4, the CPU 35C determines the chromaticity data for which the luminance exceeds the first threshold and is determined to be an achromatic color for each of the regions 1 to 12, that is, for each light source estimated to illuminate the subject. The number is counted to create histograms as shown in FIGS. 7 and 8, and the process proceeds to step S15. Here, the determination of the luminance is performed based on, for example, whether the G color signal exceeds the first threshold value. The first threshold is provided to determine whether the color signal detected by the color sensor 86 is a value necessary for light source estimation. 7 and 8, among the chromaticity data obtained by outputting 160 pixels of the color sensor 86, the chromaticity data that has the luminance necessary for estimating the light source and is determined to be an achromatic color is displayed for each light source. Classified and represented.
[0018]
In step S15, the CPU 35C increments the number of chromaticity data for which it is determined whether or not the color is achromatic, and proceeds to step S16. In step S <b> 16, the CPU 35 </ b> C determines whether or not an achromatic color has been determined for all 160 sets of chromaticity data output from the color sensor 86. If the number incremented in the process of step S15 has reached 160, CPU 35C makes an affirmative decision in step S16 and proceeds to step S17. If the incremented number is less than 160, the CPU 35C makes a negative decision in step S16 and returns to step S13. .
[0019]
In step S <b> 17, the CPU 35 </ b> C determines whether the luminance detected by the color sensor 86 exceeds the second threshold value. Here, the second threshold value is provided for determining that the luminance is sufficiently high, and the second threshold value is set to a value larger than the first threshold value. The CPU 35C makes an affirmative decision in step S17 when the G color signal is equal to or smaller than the second threshold value, and proceeds to step S18 in FIG. 5. If the value of the G color signal exceeds the second threshold value, the step is performed. A negative determination is made in S17 and the process proceeds to step S27.
[0020]
In step S18 of FIG. 5, the CPU 35C includes the largest number of chromaticity data among the regions (regions 1 to 12 in FIG. 6) indicating the chromaticity of the achromatic object illuminated by each type of light source. The area is selected, that is, the type of the light source is selected, and the process proceeds to step S19. Here, the CPU 35C estimates a light source that illuminates the subject by selecting a light source corresponding to a region where the number of included chromaticity data is maximum. In step S19, the CPU 35C determines whether or not there are two or more regions having the maximum value. If there are two or more regions, the CPU 35C makes a positive determination in step S19 and proceeds to step S20. Is negatively determined, and the process proceeds to step S22.
[0021]
In step S20, the CPU 35C determines whether or not the light sources corresponding to the selected areas include natural light (sunlight) and fluorescent light, that is, at least one of the areas 1 to 6 and the area It is determined whether or not any of 7 to 12 is included. The CPU 35C makes an affirmative decision in step S20 when sunlight and a fluorescent lamp are included, and proceeds to step S21. If only one of sunlight or a fluorescent lamp is included, the CPU 35C makes a negative determination in step S20 and proceeds to step S23. .
[0022]
In step S21, the CPU 35C selects a region having the maximum number of chromaticity data among the regions 7 to 12 by the fluorescent lamp, and uses all the data included in this region for R / G and B / G. The average value is calculated. In the process at step S21, the data of the areas 7 to 12 by the fluorescent lamp is used without using the data of the areas 1 to 6 by the sunlight. In addition, when there are two or more areas having the maximum value among the areas 7 to 12 by the fluorescent lamp, the priority order is (1) white fluorescent lamp, (2) daylight white fluorescent lamp, and (3) daylight color fluorescent lamp. A region is selected. When CPU 35C calculates the average value of R / G and B / G using all the data in the selected area, it proceeds to step S26.
[0023]
In step S22 which proceeds after making a negative determination in step S19 described above, the CPU 35C calculates an average value of R / G and B / G using all the data in the region including the largest number of chromaticity data. Proceed to S26.
[0024]
In step S23, which proceeds after making a negative determination in step S20 described above, the CPU 35C determines whether the region including the most chromaticity data is due to sunlight or fluorescent light. The CPU 35C makes an affirmative decision in step S23 when two or more areas are estimated to be fluorescent lamps, and proceeds to step S25. When the two or more areas are estimated to be sunlight, the step is performed. A negative determination is made in S23 and the process proceeds to step S24.
[0025]
In step S24, for example, the CPU 35C calculates an average value of R / G and B / G using all data included in the region 3 and the region 4, and proceeds to step S26. Here, the reason why the data in the region 3 and the region 4 is selected is to calculate the average values of R / G and B / G using the data of the sunlight region where the color temperature is close to 5000K. In step S25, which proceeds after making an affirmative determination in step S23, the CPU 35C uses all the data included in the region where the number of chromaticity data is the largest among the regions 7 to 12 by the fluorescent lamp, and uses R / G and B The average value of / G is calculated. At this time, since there are two or more areas having the maximum value among the areas 7 to 12 by the fluorescent lamp, (1) white fluorescent lamp, (2) day white fluorescent lamp, and (3) daylight color fluorescent lamp in order of priority. A region is selected. When CPU 35C calculates the average value of R / G and B / G using all the data in the selected area, it proceeds to step S26.
[0026]
In step S26, the CPU 35C calculates a correlated color temperature from the memory 35D based on the calculated average values of R / G and B / G. FIG. 9 is a diagram illustrating a correlated color temperature curve, where the horizontal axis is R / G and the vertical axis is B / G. By dividing the R signal and the B signal by the G signal, the degree of the red component and the blue component in the subject color can be expressed regardless of the subject luminance. As the color temperature increases, the blue component increases, and as the color temperature decreases, the red component increases. If the correlated color temperature curve shown in FIG. 9 is stored in advance in the memory 35D as a lookup table, the CPU 35C reads the correlated color temperature from the memory 35D in accordance with the calculation result of the average values of R / G and B / G. be able to.
[0027]
The CPU 35C determines an R gain and a B gain for white balance adjustment using the obtained correlated color temperature. FIG. 10 is a diagram illustrating the relationship between the correlated color temperature, the R gain, and the B gain. The values of the R gain and the B gain are determined in advance by actual measurement so that the color of the subject illuminated by the estimated light source is closer to the color that the human eye can see and express as a function of the color temperature. These R gain and B gain values are stored in advance in the memory 35D as a look-up table, and are read from the memory 35D in accordance with the correlated color temperature. The CPU 35C determines the white balance adjustment R gain for the R data and the white balance adjustment B gain for the B data from the correlated color temperature, and stores the determined R gain and B gain in the memory 35D. The process of 5 is finished.
[0028]
On the other hand, in step S27 that proceeds with a negative determination in step S17 described above, the CPU 35C selects an area in which the number of chromaticity data is the largest among the areas 1 to 6 due to sunlight, and proceeds to step S28. In the process at step S27, the data of the areas 1 to 6 by sunlight is used without using the data of the areas 7 to 12 by the fluorescent lamp. This is because, for example, when the value of the G color signal exceeds the above-described second threshold, sunlight is regarded as the estimated light source. In step S28, the CPU 35C determines whether or not there are two or more regions having the maximum value. If there are two or more regions, the CPU 35C makes an affirmative determination in step S28 and proceeds to step S29. Is negatively determined, and the process proceeds to step S30.
[0029]
In step S29, for example, the CPU 35C calculates an average value of R / G and B / G using all chromaticity data included in the region 3 and the region 4, and proceeds to step S26 in FIG. Here, the reason why the data in the region 3 and the region 4 is selected is to calculate the average values of R / G and B / G using data close to the sunlight region having a color temperature of 5000K. The purpose of this is to perform an appropriate gain adjustment at the time of shooting a night scene, for example, by calculating the gain using predetermined color temperature information when the light source is not estimated. In step S30, which proceeds after making a negative determination in step S28, the CPU 35C calculates an average value of R / G and B / G using all the data in the region including the largest number of chromaticity data. Proceed to step S26.
[0030]
The white balance adjustment coefficient determined as described above is used at the time of white balance adjustment performed by the image processing CPU 29 for image data captured by the image sensor 26 thereafter. The white balance adjustment is used for white balance adjustment with respect to the R signal and the B signal of the entire area imaged by the image sensor 26 regardless of the detection area of 160 pixels of the color signal by the color sensor 86 used for estimating the light source. This is performed by multiplying the R gain and the B gain of each.
[0031]
The relationship between the correlated color temperature, the R gain, and the B gain shown in FIG. 10 does not necessarily match between when shooting under natural light and when shooting under fluorescent light. In this case, it is necessary to adjust the white balance adjustment gain. Generally, the color temperature of the captured RGB data is higher when shooting under fluorescent light than when shooting under natural light. This color temperature difference can be corrected by correcting the R gain and B gain values of FIG. 10 by a predetermined amount. Therefore, look-up tables storing R gain and B gain values are used for photographing under natural light (corresponding to areas 1 to 6) and for photographing under fluorescent lamps (corresponding to areas 7 to 12). 12 sets of memory 35D are prepared, and a lookup table prepared in advance is read out from the memory 35D in accordance with the estimated type of light source.
[0032]
The features of this embodiment will be summarized.
(1) Areas 1 to 12 indicating achromatic chromaticity corresponding to sunlight having a plurality of color temperatures and a plurality of types of fluorescent lamps are provided in advance on the chromaticity coordinates, and 160 colors of the color sensor 86 are provided. Chromaticity (RG) / G and (BG) / G are calculated using the signal output. An area including the largest number of 160 sets of calculated chromaticity data is selected from the 12 areas, and a light source corresponding to the area is estimated. Since chromaticity data is detected for 160 pixels from the object scene, even if the subject color is not only achromatic but also composed of chromatic colors, any region for 160 pixels is achromatic. Therefore, there is a high possibility that chromaticity data indicating the light source exists, and the type of the light source can be estimated.
(2) Areas 1 to 12 are sunlight (natural light) having a color temperature of 3000K, 4250K, 4520K, 5120K, 6130K, and 6620K, and white, daylight white, daylight color ordinary fluorescent lamps, and three-wavelength color rendering properties. Since it corresponds to 12 types of light sources of fluorescent lamps, all general illumination light can be estimated. As a result, even if the light source changes, an appropriate white balance adjustment gain can be determined according to the emission line spectrum of each light source, and a high-quality color image can be obtained.
(3) When the value of the color signal of G color exceeds the second threshold value with which the luminance is sufficiently high, sunlight is regarded as an estimated light source (step S27). When the value of the G color signal is sufficiently large, the light source by sunlight is estimated even if the chromaticity data is contained most in any one of the regions 7 to 12 of the fluorescent lamp. In general, illumination light from a fluorescent lamp contains many G colors. If the scene contains many G colors, such as landscape photos under sunlight, and if the fluorescent lamp is mistakenly regarded as the light source, the color will be strongly corrected with the G complementary color when adjusting the white balance. This may cause color feria. Therefore, the above color feria can be prevented by regarding the case where the color signal of the G color exceeds the second threshold as sunlight.
(4) When the value of the G color signal is below the first threshold required for light source estimation, it is not counted as chromaticity data used for light source estimation and is not used for histogram creation. Since (Step S14), the signal level used for estimation is low and is not affected by noise, it is possible to estimate the light source that strongly illuminates the subject.
(5) Since the color sensor 86 is arranged in the viewfinder device 80, the color sensor 86 receives the white balance detection data before the mirror 71 is mirrored up by the operation of the full push switch 23, and the white color is detected. The balance adjustment gain can be determined and stored in the memory 35D. Therefore, since it is not necessary to determine the white balance adjustment gain in the shooting sequence performed by operating the full-press switch 23, the shooting processing time can be shortened compared to the case where the white balance adjustment gain is determined in the shooting sequence. it can.
(6) Since the relationship between the correlated color temperature, the R gain, and the B gain is stored in advance in the memory 35D as a lookup table, the time required for the arithmetic processing can be shortened.
[0033]
-Second Embodiment-
The configuration and circuit block diagram of the electronic still camera of the second embodiment are the same as the configuration of the electronic still camera of FIG. 1 of the first embodiment and the circuit block diagram of FIG. Similarly to the first embodiment, the color sensor 86 is a single two-dimensional imaging device having 480 pixels divided into 48 columns × 10 rows as shown in FIG. As in the first embodiment, the color sensor 86 divides the imaging surface into 160 areas and outputs a color signal.
[0034]
FIG. 11 is a diagram corresponding to FIG. 6 of the first embodiment, and represents an achromatic color distribution on the chromaticity coordinates in the second embodiment. A green region 13 is added to FIG. 6 of the first embodiment. In the second embodiment, whether the 160 sets of chromaticity data (RG) / G and (BG) / G calculated by the CPU 35C belong to the green region 13 is also counted.
[0035]
In the second embodiment, if the number of green regions 13 has the maximum value, the light source is determined to be sunlight and controlled. That is, even if one of the fluorescent lamp areas 7 to 12 has the next highest count after the green area 13, the light source is not determined to be a fluorescent lamp. And the largest thing is selected from the sunlight areas 1-6, and the selected color temperature is controlled as a light source. As a result, when a green subject is illuminated with sunlight, it is not erroneously determined to be illuminated by any fluorescent lamp.
[0036]
FIG. 12 is a flowchart illustrating white balance adjustment gain determination processing according to the second embodiment. It is a part corresponding to FIG. 5 of 1st Embodiment. Parts corresponding to FIG. 4 of the first embodiment will be described with reference to FIG.
[0037]
In step S13 of FIG. 4, the CPU 35C determines whether there is data indicating an achromatic color for the calculated 160 sets of chromaticity data (RG) / G and (BG) / G or in the green region 13. It is determined whether there is included data. When there is achromatic color data or data included in the green region 13, the CPU 35C makes a positive determination in step S13 and proceeds to step S14. When there is no achromatic color data and data included in the green region 13, the CPU 35C makes a negative determination in step S13. The process proceeds to step S16.
[0038]
In step S14 of FIG. 4, the CPU 35C counts the number of chromaticity data for each of the areas 1 to 13, creates a histogram as shown in FIGS. 7 and 8, and proceeds to step S15. In the second embodiment, the green region 13 is added to the histograms of FIGS. In step S15, the CPU 35C increments the number of chromaticity data in the corresponding area, and proceeds to step S16.
[0039]
In step S40 of FIG. 12, the CPU 35C determines whether or not the green region 13 includes the largest number of chromaticity data. If it is determined that the green area 13 includes the most chromaticity data, the process proceeds to step S41. In step S41, the CPU 35C determines whether or not there are two or more areas having the maximum value, that is, whether or not there are areas other than the green area 13. If there are two or more areas, the CPU 35C makes a positive determination in step S41. Proceeding to step S43, if less than two areas, a negative determination is made in step S41, and the process proceeds to step S42.
[0040]
In step S42, the CPU 35C calculates an average value of R / G and B / G using all data in the region including the largest number of chromaticity data, and proceeds to step S26. On the other hand, in step S43, for example, the CPU 35C calculates an average value of R / G and B / G using all data included in the region 3 and the region 4, and proceeds to step S26. Here, the reason why the data in the region 3 and the region 4 is selected is to calculate the average values of R / G and B / G using the data of the sunlight region where the color temperature is close to 5000K.
[0041]
In this way, in the second embodiment, a histogram is created by counting even when green is emitted when irradiated with sunlight. If the number of green regions 13 has the maximum value, the light source is determined to be sunlight and controlled. As a result, when a green subject is illuminated with sunlight, it is not erroneously determined to be illuminated by any fluorescent lamp.
[0042]
-Third embodiment-
The configuration and circuit block diagram of the electronic still camera of the third embodiment are the same as the configuration of the electronic still camera of FIG. 1 of the first embodiment and the circuit block diagram of FIG. Similarly to the first embodiment, the color sensor 86 is a single two-dimensional imaging device having 480 pixels divided into 48 columns × 10 rows as shown in FIG. As in the first embodiment, the color sensor 86 divides the imaging surface into 160 areas and outputs a color signal.
[0043]
FIGS. 13 to 15 are diagrams corresponding to FIG. 6 of the first embodiment or FIG. 11 of the second embodiment, and represent the achromatic color distribution on the chromaticity coordinates in the third embodiment. FIG. In the third embodiment, the region used for determining as an achromatic color is selected according to the luminance.
[0044]
FIG. 13 is a diagram showing the achromatic color distribution 1 on the chromaticity coordinates when the luminance Bv ≧ 7 or Bv ≦ 0. With respect to FIG. 11 of the second embodiment, region 1 and region 6 to region 13 are not set, and only region 2 to region 5 are set. This is because when the brightness Bv is brighter than 7 or when the brightness Bv is darker than 0, it is not necessary to consider a low color temperature or a high color temperature. That is, it is considered to be a scene similar to a night view or a scene directly exposed to sunlight. Further, since it is considered that a flash or the like is used even under a fluorescent lamp with low brightness, it is considered that the possibility of fluorescent lamp illumination is low.
[0045]
FIG. 14 is a diagram illustrating the achromatic color distribution 2 on the chromaticity coordinates when the luminance is 0 <Bv <4. It is the same as FIG. 11 of 2nd Embodiment, and the area | region 1-the area | region 13 are set. When the luminance is 0 <Bv <4, it is necessary to deal with all kinds of lighting such as sunlight, fluorescent lamps, light bulbs, and dusk. Also, only in this luminance range, as in the second embodiment, the green region 13 is set so that the green light under sunlight and the fluorescent lamp are not mistaken.
[0046]
FIG. 15 is a diagram illustrating the achromatic color distribution 3 on the chromaticity coordinates when the luminance is 4 ≦ Bv <7. With respect to FIG. 11 of the second embodiment, the areas 7 to 13 are not set and the areas 1 to 6 are set. In the case of luminance 4 ≦ Bv <7, the possibility of artificial light from fluorescent lamps and light bulbs is considered to be low. However, since illumination with low color temperature and high color temperature is possible, when luminance Bv ≧ 7 or Bv ≦ 0, Compared with the number of areas.
[0047]
FIG. 16 is a flowchart for explaining the flow of processing for determining the white balance adjustment gain according to the third embodiment. FIG. 5 is a part of a flowchart corresponding to FIG. 4 of the first embodiment and the second embodiment. The only difference from the flowchart of FIG. 4 is that step S40 is added after step S12. Since other steps are common, description thereof is omitted. Moreover, since it is common to the flowchart of FIG. 12 of the second embodiment, the description thereof is omitted.
[0048]
In step S40, the setting of the area determined as an achromatic color is changed according to the luminance Bv. When the brightness Bv ≧ 7 or Bv ≦ 0, the regions 2 to 5 are used. When the luminance is 0 <Bv <4, the regions 1 to 13 are used. When luminance 4 ≦ Bv <7, regions 1 to 6 are used.
[0049]
In this way, by limiting the area determined as an achromatic color according to the luminance, it is possible to prevent erroneous calculation of the color temperature due to the color feria. Note that the area selected in accordance with the luminance need not be limited to the above contents. Different cases may occur depending on various conditions and experimental results.
[0050]
In the above description, a single-lens reflex electronic still camera has been described. However, the present invention can also be applied to an electronic still camera that is not a single-lens reflex camera. In this case, subject images are separately formed on the image sensor 26 and the color sensor 86 using a beam splitter, a half mirror, or the like. The present invention can also be applied to a video camera that captures a moving image.
[0051]
In the above description, the image sensor 26 and the color sensor 86 are provided separately, but the image sensor 26 may also be used as a color sensor. In this case, the white balance adjustment gain is determined using the data imaged by the imaging device 26 as described above. Then, white balance adjustment is performed on the subject image data captured when the release operation is performed, using the white balance adjustment gain.
[0052]
The color sensor 86 described above is a two-dimensional image sensor having 480 pixels divided into 48 columns × 10 rows, and an RGB color filter 861 is provided to output color signals for 160 pixels. The pixel configuration does not have to be this.
[0053]
In the above description, the electronic camera has been described. However, the present invention is not limited to the electronic camera. For example, the present invention can be applied to a mobile phone with a CCD camera, a personal computer with a CCD camera, and the like. In other words, the present invention can be applied to any imaging device having an imaging element.
[0054]
Furthermore, a computer such as a personal computer may acquire an image signal (image data) before image processing from the image sensor as it is and perform the above-described processing by a program in the computer. In this case, the acquired image pickup signal (image data) is appropriately divided so that an image pickup signal equivalent to the image pickup signal acquired by the color sensor 86 described above is acquired. At this time, it is only necessary to appropriately select the pixels in the divided area or to obtain an average value. An imaging signal (image data) is acquired from the imaging device via an interface cable or wirelessly, or via a recording medium such as a memory card or a CD.
[0055]
When processing in a personal computer or the like, a program related to the above-described processing can be provided through a recording medium such as a CD-ROM or a data signal such as the Internet. FIG. 17 is a diagram showing this state. The personal computer 100 receives a program via the CD-ROM 104. The personal computer 100 has a connection function with the communication line 101. The computer 102 is a server computer that provides the program, and stores the program in a recording medium such as the hard disk 103. The communication line 101 is a communication line such as the Internet or personal computer communication, or a dedicated communication line. The computer 102 reads the program using the hard disk 103 and transmits the program to the personal computer 100 via the communication line 101. That is, the program is embodyed as a data signal on a carrier wave and transmitted via the communication line 101. Thus, the program can be supplied as a computer-readable computer program product in various forms such as a recording medium and a carrier wave.
[0056]
The correspondence between each constituent element in the claims and each constituent element in the embodiment of the invention will be described. The interchangeable lens 90 is the photographing lens, the color signal is the imaging signal, and the imaging device 73 (the color sensor 86). The imaging means includes (RG) / G and (BG) / G as chromaticity, and the CPU 35C serves as chromaticity detection means, light source estimation means, first luminance determination means, and second luminance determination means. , CPU 35C and memory 35D are gain calculation means, sunlight (natural light) having color temperatures of 3000K, 4250K, 4520K, 5120K, 6130K, and 6620K, and white, daylight white, daylight color ordinary fluorescent lamps, and white and daylight white, respectively. A daylight color three-wavelength color rendering fluorescent lamp, the correlated color temperature curve represented on the R / GB / G coordinates, and the gain for adjusting the correlated color temperature and white balance The relationship is the color temperature information, the image processing CPU 29 is the gain adjustment means, the achromatic color distribution on the chromaticity coordinates is the chromaticity information, each of 160 pixels of the color sensor 86 is in a predetermined area, and the first threshold is The second threshold corresponds to the first predetermined value, and the second threshold corresponds to the second predetermined value.
[0057]
【The invention's effect】
As described above in detail, the present invention has the following effects.
(1) Claims 1 to 9 According to the invention described in the above, it is possible to estimate a light source that illuminates the subject based on an imaging signal output by imaging the subject and perform image processing based on the type of the light source, so that a high-quality image can be obtained. Become.
(2) In the imaging device according to the first to eighth aspects of the present invention, the chromaticity of the subject is detected using an imaging signal output by imaging the subject, and a light source that illuminates the subject using the chromaticity is provided. Then, gain adjustment is performed on the image signal with the gain calculated based on the color temperature information corresponding to the estimated light source. Therefore, even if the light source that illuminates the subject changes, gain adjustment is performed with the color temperature information corresponding to the estimated light source. As a result, appropriate white balance adjustment can be performed, and a high-quality image can be obtained. Become.
(3) In the inventions according to claims 1 to 8, a plurality of chromaticity information is given in advance corresponding to a plurality of predetermined light sources, and a light source corresponding to the chromaticity information substantially matching the detected chromaticity of the subject is provided. Since the estimation is performed, the estimation process can be simplified as compared with the case of estimating the light source so as to be strictly matched.
(4) In particular, in the invention described in claim 5, since chromaticity information is provided corresponding to sunlight at a plurality of color temperatures and a plurality of types of fluorescent lamps, the light source used during normal photographing is used. All can be estimated. In addition, since the chromaticity information of almost achromatic colors is given discretely, the achromatic part of the subject is used for light source estimation, so that the subject color (chromatic part) affects the light source estimation. There is no.
(5) In particular, in the invention described in claim 6, the chromaticity is detected for each predetermined region obtained by dividing the object scene, and the number of light sources estimated for each region (for example, the largest number) (Estimated) After considering one type of light source as the light source of the subject, for example, the gain is calculated with the color temperature information corresponding to the average value of the chromaticity used when estimating the many estimated light sources. did. Therefore, even when the subject color is not only an achromatic color but also a chromatic color, the chromaticity indicating an achromatic color is detected in any region, so that the type of the light source can be estimated. Further, since the chromaticity detected in the region having a luminance higher than the first predetermined value is used, the light source that illuminates the subject can be correctly estimated.
(6) In particular, in the inventions according to claims 1 to 8, when a luminance higher than the second predetermined value is detected, one type is used instead of a fluorescent lamp depending on the number of light sources estimated for each region. The gain is calculated using the color temperature information corresponding to the average value of the chromaticity used when estimating the estimated sunlight. Therefore, for example, when a subject contains a lot of G color as in landscape photography under bright sunlight, color feria is prevented by regarding it as sunlight instead of a fluorescent lamp with a large G color component. be able to.
(7) In particular, in the invention described in claim 7, since the gain is calculated using predetermined color temperature information determined in advance when the light source is not estimated, for example, a white balance appropriate for shooting night scenes or the like. Adjustments can be made.
(8) In particular, in the invention described in claim 8, since the look-up table for outputting the gain with the light source and color temperature information as arguments is provided, the gain determination processing time can be shortened compared with the arithmetic processing. it can.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a first embodiment of a single-lens reflex electronic still camera.
FIG. 2 is a block diagram showing a first embodiment of a signal processing system of a single-lens reflex electronic still camera.
FIG. 3 is a diagram illustrating a filter arrangement of the color sensor according to the first embodiment.
FIG. 4 is a flowchart showing white balance adjustment gain determination processing according to the first embodiment;
FIG. 5 is a flowchart illustrating white balance adjustment gain determination processing according to the first embodiment;
FIG. 6 is a diagram illustrating an achromatic color distribution on chromaticity coordinates according to the first embodiment.
FIG. 7 is a diagram illustrating a histogram for each region according to the first embodiment;
FIG. 8 is a diagram illustrating a histogram for each region according to the first embodiment;
FIG. 9 is a diagram of a correlated color temperature curve represented on R / GB / G coordinates according to the first embodiment.
FIG. 10 is a diagram illustrating a relationship between a correlated color temperature and a white balance adjustment gain according to the first embodiment.
FIG. 11 is a diagram illustrating an achromatic color distribution on chromaticity coordinates in the second embodiment.
FIG. 12 is a flowchart illustrating white balance adjustment gain determination processing according to the second embodiment;
FIG. 13 is a diagram illustrating an achromatic color distribution 1 on chromaticity coordinates in the third embodiment.
FIG. 14 is a diagram illustrating an achromatic color distribution 2 on chromaticity coordinates in the third embodiment.
FIG. 15 is a diagram illustrating an achromatic color distribution 3 on chromaticity coordinates in the third embodiment.
FIG. 16 is a flowchart illustrating a flow of processing for determining a white balance adjustment gain according to the third embodiment;
FIG. 17 is a diagram illustrating a state in which a program is provided through a recording medium such as a CD-ROM or a data signal such as the Internet.
[Explanation of symbols]
21, 35C ... CPU, 22 ... half-press switch,
23 ... Full press switch, 26 ... Image sensor,
28, 35B ... A / D conversion circuit, 29 ... Image processing CPU,
32 ... Viewfinder, 33 ... JPEG compression circuit,
35 ... White balance detection circuit, 35D ... Memory,
73 ... Imaging device, 86 ... Color sensor,
90 ... Interchangeable lens, 861 ... Color filter

Claims (9)

An image pickup means for picking up an image of a subject passing through the taking lens and outputting an image pickup signal;
Chromaticity detection means for detecting the chromaticity of the subject;
Light source estimation means for estimating the type of light source that illuminates the subject using chromaticity detected by the chromaticity detection means;
Gain calculating means for calculating gain using color temperature information corresponding to the light source estimated by the light source estimating means;
Gain adjustment means for performing gain adjustment by applying a gain calculated by the gain calculation means to the imaging signal output from the imaging means;
A second luminance determining means for determining whether or not the luminance for each predetermined area obtained by dividing the subject is higher than a second predetermined value;
The light source estimation unit estimates the types of the plurality of light sources using the chromaticity detected in each region for each region, when the second luminance determination unit determines that the luminance is high. Depending on the number of light sources estimated in the area, one type of sunlight is considered as the light source of the subject,
The gain calculating unit calculates an average of chromaticity used when the light source estimating unit considers the light source of the subject, and calculates a gain using color temperature information corresponding to the calculated average value. An imaging device. The imaging apparatus according to claim 1,
The chromaticity detection unit detects the chromaticity of the subject based on the imaging signal output from the imaging unit. The imaging apparatus according to claim 1,
The chromaticity detection unit includes a chromaticity detection imaging unit that images the subject and outputs a chromaticity detection imaging signal separately from the imaging unit, and is output from the chromaticity detection imaging unit. An image pickup apparatus that detects chromaticity of the subject based on an image pickup signal for chromaticity detection. The imaging device according to any one of claims 1 to 3,
The light source estimation means corresponds to chromaticity information that substantially matches the chromaticity detected by the chromaticity detection means from among a plurality of chromaticity information given in advance corresponding to a plurality of predetermined light sources. An imaging device characterized by estimating a light source. The imaging apparatus according to claim 4,
The plurality of predetermined light sources are sunlight at a predetermined plurality of color temperatures, and a predetermined plurality of types of fluorescent lamps,
The imaging apparatus according to claim 1, wherein the chromaticity information is discretely given so as to show a substantially achromatic color under illumination by each of the sunlight and each of the fluorescent lamps. In the imaging device according to any one of claims 1 to 5,
A first luminance determining means for determining whether or not the luminance for each predetermined area obtained by dividing the object scene is higher than a first predetermined value;
The chromaticity detection means detects the chromaticity of the subject for each of the predetermined areas,
The light source estimation unit estimates the types of the plurality of light sources using the chromaticity detected in the region for each region determined to have high luminance by the first luminance determination unit, and is estimated in each region. Depending on the number of light sources, one type of light source is considered as the light source of the subject,
The gain calculating unit calculates an average of chromaticity used when the light source estimating unit considers the light source of the subject, and calculates a gain using color temperature information corresponding to the calculated average value. An imaging device. The imaging apparatus according to claim 1,
The gain calculating means calculates a gain using predetermined color temperature information determined in advance when sunlight of any color temperature is not regarded as the light source of the subject by the light source estimating means. Imaging device. In the imaging device according to any one of claims 1 to 7,
The imaging apparatus, wherein the gain calculating means includes a light source that illuminates the subject and an LUT that outputs the gain using the color temperature information as an argument. In the imaging device according to any one of claims 1 to 8 ,
The imaging apparatus is an electronic camera.

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