JP2004222182A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a noise amount of a final image from increasing by picked up image data with a bad S/N due to low sensitivity pixels. <P>SOLUTION: A digital camera is provided with a solid-state image pickup element having the low sensitivity pixels and high sensitivity pixels, an exposure time determining means for determining whether an exposure period of time for photographing is equal to or greater than a prescribed threshold, and a control means for outputting image data read from the high sensitivity pixels when the exposure time determining means determines that photographing is performed for an exposure period of time that is equal to or greater than the prescribed threshold and for combining the image data read from the high sensitivity pixels with image data read from the low sensitivity pixels to output the combined image data when the exposure time determining means determines that photographing is performed for an exposure period of time which is less than the prescribed threshold. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera equipped with a solid-state imaging device having both low-sensitivity pixels and high-sensitivity pixels.
[0002]
[Prior art]
In digital cameras such as digital still cameras and digital video cameras, the saturation amount of charge accumulated in the photodiodes that make up each pixel of the solid-state image sensor decreases as the number of pixels increases, that is, the photodiodes become smaller. Has a drawback that the dynamic range becomes narrow.
[0003]
In order to overcome this drawback, for example, in the conventional technique described in Japanese Patent Application Laid-Open No. 2001-8104, a solid-state image sensor is provided with two types of pixels, a high-sensitivity pixel and a low-sensitivity pixel, and a captured image obtained from the high-sensitivity pixel. The dynamic range of the captured image is expanded by combining the data and the captured image data obtained from the low sensitivity pixels.
[0004]
In addition, when the number of pixels of a solid-state image sensor is increased as in recent years, an image equivalent to a silver salt camera is picked up. For this reason, captured image data output from the solid-state image sensor is RAW data (raw data of captured image data output from the solid-state image sensor) is stored in the memory without being processed without white balance correction, gamma correction, JPEG compression, etc., and this image data is read by a personal computer or the like. There is an increasing demand for users to perform white balance correction, gamma correction, color tone correction, etc. according to their own preferences. For this reason, digital cameras record image data as RAW data as described in JP-A-11-261933 (Patent Document 2) and JP-A-2001-2231979 (Patent Document 3). Is increasing.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-8104 [Patent Document 2]
JP-A-11-261933 [Patent Document 3]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-223979
[Problems to be solved by the invention]
Conventional digital cameras that capture low-sensitivity image data with low-sensitivity pixels and high-sensitivity image data with high-sensitivity pixels uniformly synthesize and output low-sensitivity image data and high-sensitivity image data. End up. For this reason, for example, in the case of a shooting situation where long exposure shooting is performed at night, that is, in a shooting situation where even a high-sensitivity pixel has a small amount of signal charge accumulation, the low-sensitivity pixel has almost no signal charge accumulation amount. There are cases where almost all of the charge is due to noise. Even in such a case, there is a problem that when the image data of the high sensitivity pixel and the image data of the low sensitivity pixel are combined and output, the combined image becomes a very noisy image.
[0007]
In addition, when the captured image data is output to the memory as RAW data and recorded, both low-sensitivity image data and high-sensitivity image data are recorded, or the low-sensitivity captured image data and high-sensitivity image data are recorded with a digital camera. Sensitive captured image data is combined and the combined captured image data is output to the memory and recorded. However, when the captured image data is output to the memory and recorded as RAW data, the low-sensitivity pixels are accumulated as described above. If there is a high probability that the electric charge is almost noise, recording low-sensitivity captured image data in the memory wastes memory capacity, and recording the combined captured image data in the memory increases the noise in the image. There is a problem of end.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a digital camera that can always output image data with good image quality regardless of shooting conditions when both image data by low sensitivity pixels and image data by high sensitivity pixels are imaged. It is in.
[0009]
[Means for Solving the Problems]
A digital camera that achieves the above object includes a solid-state imaging device having a low-sensitivity pixel and a high-sensitivity pixel, an exposure time determination unit that determines whether or not an exposure time of shooting is equal to or greater than a predetermined threshold, and the exposure time determination unit When it is determined that shooting is performed with an exposure time that is equal to or greater than the predetermined threshold, the image data read from the high-sensitivity pixel is output, and the exposure time determination unit performs shooting with an exposure time that does not satisfy the predetermined threshold. When it is determined to be performed, the image processing apparatus includes a control unit that synthesizes and outputs the image data read from the low sensitivity pixel to the image data read from the high sensitivity pixel.
[0010]
With this configuration, the imaged image data from the low-sensitivity pixels is not used at the time of shooting when the accumulated charge amount of the low-sensitivity pixels is very small, so that noise in the image can be reduced even when a dark scene is shot.
[0011]
The above-described digital camera includes a solid-state imaging device having a low-sensitivity pixel and a high-sensitivity pixel, an exposure time determination unit that determines whether or not an exposure time for shooting is equal to or greater than a predetermined threshold, and the exposure time determination unit includes: When it is determined that shooting is performed with an exposure time equal to or greater than the predetermined threshold, the image data read from the high-sensitivity pixel is output as RAW data, and the exposure time determination means has an exposure time less than the predetermined threshold. When it is determined that shooting is performed, the image processing apparatus includes a control unit that outputs the image data read from the high sensitivity pixel and the image data read from the low sensitivity pixel as RAW data. .
[0012]
With this configuration, when it is estimated that the amount of noise mixed in the image data obtained from the low-sensitivity pixels is large, only the image data obtained from the high-sensitivity pixels is output as RAW data. Even in shooting, noise in the image can be reduced.
[0013]
The control unit of the digital camera discards the image data read from the low sensitivity pixel when the exposure time determination unit determines that shooting is performed with an exposure time that is equal to or greater than the predetermined threshold, or from the low sensitivity pixel. The image data reading is stopped.
[0014]
With this configuration, when the exposure time is equal to or greater than the predetermined threshold, captured image data of low-sensitivity pixels that are not used may be discarded after being read out or may not be read out.
[0015]
Instead of the exposure time determining means of the digital camera, there is provided a setting sensitivity determining means for determining whether or not the sensitivity setting is equal to or higher than a predetermined sensitivity.
[0016]
With this configuration, use or non-use of captured image data by low-sensitivity pixels can be selected by sensitivity setting (either manual setting or auto setting may be used).
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a configuration diagram of a digital still camera according to an embodiment of the present invention. In this embodiment, a digital still camera will be described as an example. However, the present invention can also be applied to other types of digital cameras such as a camera mounted on a small electronic device such as a digital video camera or a mobile phone.
[0019]
The digital still camera shown in FIG. 1 includes a photographic lens 10, a solid-state image sensor 11, a diaphragm 12 provided between them, an infrared cut filter 13, and an optical low-pass filter 14. The CPU 15 that controls the entire digital still camera controls the light emitting unit 16 and the light receiving unit 17 for flash, controls the lens driving unit 18 to adjust the position of the photographing lens 10 to the focus position, and stops the aperture driving unit. The opening amount of the diaphragm 12 is controlled via 19 to adjust the exposure amount to an appropriate exposure amount.
[0020]
Further, the CPU 15 drives the solid-state image sensor 11 via the image sensor driving unit 20 and outputs the subject image captured through the photographing lens 10 as a color signal. In addition, a user instruction signal is input to the CPU 15 through the operation unit 21, and the CPU 15 performs various controls according to the instruction.
[0021]
The electric control system of the digital still camera includes an analog signal processing unit 22 connected to the output of the solid-state imaging device 11, and an A / D conversion that converts RGB color signals output from the analog signal processing unit 22 into digital signals. The circuit 23 is provided and these are controlled by the CPU 15.
[0022]
Further, the electric control system of this digital still camera includes a memory control unit 25 connected to the main memory 24, a digital signal processing unit 26 described later in detail, and compresses the captured image into a JPEG image and decompresses the compressed image. Mounted on the back side of the camera, the compression / decompression processing unit 27, the integration unit 28 for integrating the photometric data and adjusting the white balance gain, the external memory control unit 30 to which the removable recording medium 29 is connected. And a display control unit 32 to which the liquid crystal display unit 31 is connected. These are connected to each other by a control bus 33 and a data bus 34, and are controlled by a command from the CPU 15.
[0023]
The digital signal processing unit 26, the analog signal processing unit 22, the A / D conversion circuit 23, and the like shown in FIG. 1 can be mounted on the digital still camera as separate circuits. It is preferable to manufacture on the same semiconductor substrate using LSI manufacturing technology to form one solid-state imaging device.
[0024]
FIG. 2 is a pixel arrangement diagram of the solid-state imaging device 11 used in the present embodiment. The pixel 1 in the CCD portion that captures an image with a wide dynamic range has a pixel arrangement described in, for example, Japanese Patent Laid-Open No. 10-136391, and each pixel in the odd row is horizontally aligned with each pixel in the even row. A vertical transfer path (not shown) that is arranged with a ½ pitch shift and transfers signal charges read from each pixel in the vertical direction is meandered so as to avoid each pixel in the vertical direction. ing.
[0025]
In the illustrated example, each pixel 1 according to the present embodiment includes a low-sensitivity pixel (sub-pixel) 2 that occupies about 1/5 of the area of the pixel 1 and a high-sensitivity pixel (subpixel) that occupies the remaining about 4/5. Main signal) 3 so that the signal charge of each low-sensitivity pixel 2 and the signal charge of each high-sensitivity pixel 3 can be distinguished and transferred to the vertical transfer path. . It should be noted that the ratio and the position at which the pixel 1 is divided are determined by design, and FIG. 2 is merely an example.
[0026]
The solid-state imaging device 11 has been described by taking a CCD having a honeycomb pixel arrangement as shown in FIG. 2 as an example, but may be a Bayer CCD or a CMOS sensor.
[0027]
The digital camera of the present embodiment has a captured image data output mode, a completed image output mode and a RAW data output mode, and the completed image output mode includes a composite image output mode and a non-synthesized image output mode. The RAW data output mode includes a low sensitivity image data output mode and a low sensitivity image data non-output mode.
[0028]
The composite image output mode of the completed image output mode is a low-sensitivity image data (image data obtained by the low-sensitivity pixel 2) obtained by one imaging and a high-sensitivity image data (obtained by the high-sensitivity pixel 3). As will be described later in detail, the image data) is synthesized to generate a completed image, which is output and recorded on the recording medium 29.
[0029]
The non-composite image output mode of the completed image output mode means that the low-sensitivity image data read from the low-sensitivity pixels is discarded or the image data is not read from the low-sensitivity pixels (in the description of the following embodiment, An example of discarding will be described.) In this mode, a completed image is generated and output only from high-sensitivity image data, and is recorded on the recording medium 29.
[0030]
The low-sensitivity image data output mode of the RAW data output mode is a mode in which both low-sensitivity image data and high-sensitivity image data are output as RAW data and recorded on the recording medium 29.
[0031]
The low-sensitivity image data non-output mode of the RAW data output mode means that the low-sensitivity image data read from the low-sensitivity pixels is discarded or the image data is not read from the low-sensitivity pixels (description of the following embodiment) Now, an example of discarding will be described.) In this mode, only high-sensitivity image data is output as RAW data and recorded on the recording medium 29.
[0032]
Whether the output mode of the image data is the completed image output mode or the RAW data output mode is determined by the user inputting an instruction from the operation unit 21 to select the composite image output mode or the non-composite image output mode. Alternatively, the CPU 15 determines and selects whether to use the low-sensitivity image data output mode or the low-sensitivity image data non-output mode according to shooting conditions such as the shutter speed, exposure amount, and shooting mode.
[0033]
FIG. 3 is a diagram for explaining the operation of the digital still camera described above. An analog high-sensitivity image signal H output from the high-sensitivity pixel 3 of the solid-state image sensor 11 is converted into, for example, 10-bit digital data by the A / D converter 23 and output from the low-sensitivity pixel 2 of the solid-state image sensor 11. The analog low-sensitivity image signal L is converted into, for example, 8-bit digital data by the A / D converter 23.
[0034]
When the user sets the completed image output mode with the operation unit 21, the digital signal processing unit 26 takes in the 10-bit high sensitivity image data and the 8-bit low sensitivity image data output from the A / D converter 23. In composite image output mode, both image data are combined and other image processing is performed to generate completed image data. In non-composite image output mode, low-sensitivity image data is discarded and high-sensitivity image data is used to complete the image. The external memory control unit (recording circuit) 30 generates data, for example, a JPEG-compressed completed image passed from the digital signal processing unit 26 via the compression / decompression processing unit 27 (not shown in FIG. 3) in FIG. Data is output to the recording medium 29 and recorded.
[0035]
When the user sets the RAW data output mode with the operation unit 21, the 10-bit high sensitivity image data and the 8-bit low sensitivity image data output from the A / D converter 23 are converted into the low sensitivity image data output mode. In both cases, the external memory control unit 30 outputs and records the data on the recording medium 29 as it is. In the low-sensitivity image data non-output mode, the low-sensitivity image data is discarded and only the high-sensitivity image data is directly stored on the recording medium 29. Output and record.
[0036]
FIG. 4 is a processing configuration diagram of the digital signal processing unit 26 that operates in the completed image output mode. Hereinafter, the case of the composite image output mode will be described as an example. However, in the non-composite image output mode, the low-sensitivity image data is discarded at the time of input, and a completed image is generated and output only from the high-sensitivity image data.
[0037]
The digital signal processing unit 26 employs a logarithmic addition method in which high-sensitivity image data and low-sensitivity image data are each subjected to gamma correction and then subjected to addition processing, and the high-sensitivity image output from the A / D conversion circuit 23 is used. An offset correction circuit 41a that takes an RGB color signal that is a digital signal and performs an offset process, a gain correction circuit 42a that white balances an output signal of the offset correction circuit 41a, and a gamma correction for the color signal after gain correction. A gamma correction circuit 43a for performing, an offset correction circuit 41b for performing an offset process by taking in RGB color signals which are digital signals of low-sensitivity images output from the A / D conversion circuit 23 shown in FIG. 1, and an offset correction circuit 41b The gain correction circuit 42b for white balance of the output signal and the color signal after gain correction And a gamma correction circuit 43b for performing gamma correction. When linear matrix processing or the like is performed on the signal after offset correction, it is performed between the gain correction circuits 42a and 42b and the gamma correction circuits 43a and 43b.
[0038]
The digital signal processing unit 26 further interpolates the RGB color signal after the image composition by performing an image composition process by taking both output signals of each of the gamma correction circuits 43a and 43b and performing image composition processing. Reduces noise from the RGB interpolation calculation unit 45 for obtaining RGB three-color signals, the RGB / YC conversion circuit 46 for obtaining the luminance signal Y and the color difference signals Cr and Cb from the RGB signal, and the luminance signal Y and the color difference signals Cr and Cb. A noise filter 47, a contour correction circuit 48 that performs contour correction on the luminance signal Y after noise reduction, and a color difference matrix circuit 49 that performs color correction by multiplying the color difference signals Cr and Cb by the color difference matrix. Prepare.
[0039]
The above-described image composition processing circuit 44 synthesizes the high-sensitivity image data output from the gamma correction circuit 43a and the low-sensitivity image data output from the gamma correction circuit 43b in units of pixels based on the following equation 1. Output.
[0040]
[Expression 1]
data = [high + MIN (high / th, 1) × low] × MAX [(−k × high / th) + α, p]
Here, high: data after gamma correction of high sensitivity (high output) image signal low: data after gamma correction of low sensitivity (low output) image signal p: total gain (total gain)
k: coefficient th: threshold α: value determined by the scene (≈1)
It is. Note that α = 1 may be fixed.
[0041]
If the data after gamma correction is 8-bit data (256 gradations), the threshold value th is designated by, for example, “219” of the value 0 to 255 and the user of the digital still camera or the designer of the digital still camera. The value to be
[0042]
FIG. 5 is a graph showing how the MIN (high / th, 1) in Equation 1 changes. As shown in FIG. 5, the first term of Equation 1 adds the low-sensitivity image data low as it is to the high-sensitivity image data high when the high-sensitivity image data high exceeds the threshold value th. When high does not reach the threshold th, it indicates that a value obtained by multiplying the ratio of the high sensitivity image data high to the threshold th by the low sensitivity image data low is added to the high sensitivity image data high.
[0043]
In the present embodiment, the addition data obtained in the first term is not used as the synthesized image data as it is, but the second term (MAX [(− k × high / th) + α, p]) is added to the first term. A value obtained by multiplying is used as composite image data. FIG. 6 is a diagram showing a change state when k = 0.2 in MAX [(− k × high / th) + α, p].
[0044]
In the second term, the coefficient “k” is preferably a value “0.2” in the solid-state imaging device 11 of the embodiment shown in FIG. When the signal charge saturation ratios of the high-sensitivity pixel 3 and the low-sensitivity pixel 2 are different as in the solid-state imaging device 11 shown in FIG. 2, the coefficient k can be conveniently obtained by the following equation 2.
[0045]
[Expression 2]
Coefficient k = 1−Sh / (Sh + Sl)
Here, Sh: signal charge saturation amount of high sensitivity pixel Sl: signal charge saturation amount of low sensitivity pixel
In the example shown in FIG. 2, the area ratio of the photodiode does not become the saturation ratio as it is, but it can be regarded as an area ratio for convenience, and when the above example is applied,
k = 1-4 / (4 + 1) = 1-0.8
= 0.2
It becomes.
[0047]
The solid-state imaging device having both high-sensitivity pixels and low-sensitivity pixels is not limited to that illustrated in FIG. 2, and for example, as shown in FIG. 7, a large number of photodiodes (not shown) formed in the same size and shape. It is conceivable to change the aperture area of the microlens provided on top of the above and provide the high-sensitivity pixel 3 and the low-sensitivity pixel 2. In this case, the saturation amount of the signal charge of the high-sensitivity pixel and the low-sensitivity pixel is the same, and thus Equation 2 cannot be applied. However, the value of the coefficient k is obtained experimentally or from the opening area of a microlens or the like. Equation 1 can be applied by obtaining the coefficient value. The value of the coefficient k is a value that is determined by the configuration of the solid-state imaging device, and is not arbitrarily changed by the user, but is set to a fixed value when the imaging apparatus is shipped.
[0048]
In Equation 1, an experimentally determined value is used as the value of the total gain p in this embodiment. p is a gain for the entire composite image data, and the dynamic range of the image can be controlled by controlling the value of p.
[0049]
The parameter value of p is variable, but the lower limit value pmin is also determined by the following equation (3).
[0050]
[Equation 3]
pmin = Sh / (Sh + Sl)
[0051]
For digital cameras that have a maximum final output when the high-sensitivity image data is output at the maximum value, the high-sensitivity image data is set so that the combined value of the high-sensitivity image data and the low-sensitivity image data becomes the maximum value. And gain operation is required for low-sensitivity image data. That is, when high-sensitivity image data and low-sensitivity image data corresponding to the saturation amount are output from the solid-state imaging device, the output value is multiplied by a gain corresponding to pmin (<1), and the final output value becomes the maximum value. Therefore, it is necessary to convert the image data.
[0052]
For example, when the saturation ratio of the high sensitivity pixel and the low sensitivity pixel is 4: 1, pmin = 4 / (4 + 1) = 0.8
Therefore, p = pmin may be set for a high-contrast shooting scene, and the total gain p is set to a value larger than pmin for a shooting scene with low contrast.
[0053]
The smaller the total gain p value, the wider the dynamic range, and the larger the value, the narrower the dynamic range. Specifically, in a high-contrast shooting scene (such as midsummer clear sky), p = 0.8, p = 0.86 in cloudy or shaded, p = 0.9 under indoor fluorescent lamp, and so on. The value of p is changed according to. Thereby, when the data after gamma correction is 8-bit data, the 8-bit gradation value can be used more effectively.
[0054]
Even if the user sets the value of p by specifying the type of scene using the operation unit 21 shown in FIG. 1, the digital still camera itself can change the scene of the captured image based on the detection values of various sensors. Automatic determination and automatic setting may be used. For example, the white balance gain amount is obtained from the integrated value of the photometric data obtained by the integrating unit 28. Since the scene can be automatically determined from the white balance value, the value of p can be automatically set. .
[0055]
FIG. 8 is a diagram showing how the dynamic range changes when the value of p is changed. When the total gain p is increased, the characteristic line a has a small dynamic range, and when the total gain p is decreased, the characteristic line a changes to a characteristic line B having a large dynamic range.
[0056]
As described above, in the composite image output mode of the completed image output mode of the present embodiment, the high gain image data and the low sensitivity image data are added and then multiplied by the total gain according to the shooting scene. An image with a wide dynamic range can be generated. In addition, since the logarithmic addition method is employed to combine the images after reducing the number of bits of the high-sensitivity image data and the low-sensitivity image data, the circuit scale can be reduced and the cost can be reduced.
[0057]
Although the composite image output mode in the completed image output mode has been described in detail above, in the non-composite image output mode in the completed image output mode, the low-sensitivity image data is discarded, and only the high-sensitivity image data is shown in FIG. Offset correction, gain correction, gamma correction, and RGB interpolation processing, RGB / YC conversion processing, noise reduction processing, contour correction, and color difference matrix processing are performed, and the resulting luminance signal Y and color difference signals Cr and Cb are combined. As in the image output mode, the compression / decompression processing unit 27 in FIG.
[0058]
FIG. 9 shows the CPU 15 instructing the digital signal processing unit 26 to determine whether to output image data in the composite image output mode or to output image data in the non-composite image mode in the completed image output mode. It is a flowchart which shows the determination procedure.
[0059]
First, the user of the digital still camera sets an ISO sensitivity similar to the ISO sensitivity of the silver halide film camera by using the operation unit 21 in FIG. 1 (step S1). The CPU 15 takes in the input setting data and determines whether or not the set ISO sensitivity is equal to or higher than a predetermined threshold sensitivity. For example, it is determined whether the set ISO sensitivity is ISO 1600 or more (step S2).
[0060]
If the determination result in step S2 is affirmative (YES), that is, if it is determined that the ISO sensitivity is high and the accumulated charge of the low-sensitivity pixel 2 is small and the ratio of the noise component is large, the process proceeds to step S3 and the digital signal processing unit 26 The non-composite image output mode is not executed and the low-sensitivity image data is not combined with the high-sensitivity image data.
[0061]
If the determination result in step S2 is negative (NO), that is, it is determined that the ISO sensitivity is not high and the ratio of the noise component of the accumulated charge of the low-sensitivity pixel 2 is small, the process proceeds to step S4 and is combined with the digital signal processing unit 26. An image output mode is executed to synthesize low-sensitivity image data with high-sensitivity image data.
[0062]
In step S1, the user has set the sensitivity. However, the digital still camera itself may automatically set the sensitivity.
[0063]
FIG. 10 is a flowchart showing a processing procedure instead of FIG. 9 performed when the CPU 15 is in the completed image output mode. The user of the digital still camera sets the shooting mode using the operation unit 21 in FIG. 1 (step S11). When this setting is made, the CPU 15 determines whether or not the shooting mode is the night view mode (step S12). If the determination result is negative (NO) and the night scene mode is not set, the process advances to step S13 to cause the digital signal processing unit 26 to execute the composite image output mode, and the low-sensitivity image data is combined with the high-sensitivity image data.
[0064]
If the determination result in step S12 is affirmative (YES), that is, in the night scene mode, the shutter speed can be used until it is late, so the process proceeds to step S14 to perform photometry, which is determined based on the photometry result. It is determined whether the shutter speed is greater than a predetermined threshold (step S15). For example, it is determined whether the shutter speed is 1 second or more.
[0065]
If the determination result in step S15 is negative (NO), that is, if the exposure amount can be taken to some extent according to the photometric result, it is expected that the accumulated charge of the low-sensitivity pixel is significant. The signal processing unit 26 is caused to execute the composite image output mode.
[0066]
If the determination result in step S15 is affirmative (YES), that is, if the shutter speed is 1 second or longer and signal charge cannot be accumulated unless exposed for a long time, the noise component amount of the accumulated charge of the low-sensitivity pixel Therefore, the process proceeds to step S16, and the digital signal processing unit 26 is not allowed to execute the non-synthesized image output mode, and the low-sensitivity image data is not synthesized with the high-sensitivity image data.
[0067]
As described above, in this embodiment, the determination as to whether or not the low-sensitivity image data and the high-sensitivity image data are to be combined is performed according to the photometry result only in the night scene mode. That is, the photometric operation in step S14 of the present embodiment is performed in order to obtain the shutter speed in the night scene mode, and the photometric operation itself is performed in other shooting modes other than the night scene mode.
[0068]
FIG. 11 is a flowchart showing a processing procedure in place of FIG. 10 performed when the CPU 15 is in the completed image output mode. First, the user of the digital still camera sets the shooting mode from the operation unit 21 in FIG. 1 (step S21). In the next step S22, the CPU 15 determines whether or not the user-set shooting mode is the manual mode or the shutter priority mode. The long shutter area (the area where the shutter speed is slower than the threshold) can be set only in a system that can intentionally operate the shutter speed. Therefore, long shutter is possible with shutter priority, but long with aperture priority. Since shutter photography is not possible, the determination in step S22 is performed. If the determination result is not the manual mode and the shutter priority mode is not selected, the process proceeds to step S23, and the digital signal processing unit 26 is caused to execute the composite image output mode.
[0069]
If the result of determination in step S22 is manual mode or shutter priority mode, then control proceeds to step S24, where it is determined whether or not the shutter speed is greater than a predetermined threshold, for example, 1 second. If the determination result is negative (NO), the process proceeds to step S23, and the digital signal processing unit 26 is caused to execute the composite image output mode.
[0070]
If the determination result in step S24 is affirmative (YES), it can be determined that a significant signal charge cannot be accumulated unless the shutter speed is increased and the exposure time is long, and the process proceeds to step S25. Then, the digital signal processing unit 26 is caused to execute the non-synthesized image output mode.
[0071]
When the night view mode, the manual shooting mode, and the shutter priority shooting mode are mixed as the shooting mode of the digital camera, the processing procedure of FIG. 11 is executed, and the processing procedure of FIG. 10 is performed before step S23. Will be executed.
[0072]
As described above with reference to FIGS. 9, 10, and 11, the CPU 15 determines the shooting situation, and if significant signal charge can be expected to be accumulated in the low sensitivity pixels, the CPU 15 increases the captured image data by the low sensitivity pixels. When combined with the sensitivity image data and significant signal charge cannot be expected to be accumulated in the low-sensitivity pixels, and it is judged that there are many noise components, the captured image data from the low-sensitivity pixels is not used for generating the completed image. Regardless of the shooting situation, it is possible to obtain a good image with less noise components.
[0073]
Even in the RAW data output mode, the CPU 15 selects the low-sensitivity image data output mode and the low-sensitivity image data non-output mode based on the shooting situation. This selection determination process is the same as that in FIG. 9, FIG. 10, and FIG. 11 described above. When the process proceeds to step S3, step S16, or step S25, the low-sensitivity image non-output mode is executed and only the high-sensitivity image data is displayed. Is output as RAW data and recorded on the recording medium 29. When the process proceeds to step S4, step S13, or step S23, the low sensitivity image data output mode is executed, and both the high sensitivity image data and the low sensitivity image data are output as RAW data and recorded on the recording medium 29. .
[0074]
By providing this low-sensitivity image data non-output mode, the amount of data stored in the recording medium 29 can be reduced, and the recording speed can be increased. Note that the low-sensitivity image data is not recorded so that the RAW data reading device can easily determine that there is no low-sensitivity image data on the recording medium 29 and can generate a completed image from only the high-sensitivity image data by application software. The mode is preferably recorded on the recording medium 29 as tag information. This makes it possible to avoid errors in the corresponding application software.
[0075]
【The invention's effect】
According to the present invention, it is possible to always output image data with good image quality regardless of the shooting situation when both image data by low-sensitivity pixels and image data by high-sensitivity pixels are imaged.
[Brief description of the drawings]
FIG. 1 is a block diagram of a digital still camera according to an embodiment of the present invention.
FIG. 2 is a schematic surface view of the solid-state imaging device shown in FIG.
3 is an operation explanatory diagram of the digital still camera shown in FIG. 1. FIG.
4 is a processing configuration diagram of a digital signal processing unit shown in FIG. 3. FIG.
FIG. 5 is an explanatory diagram of mathematical expressions that are arithmetically processed in a composite image output mode according to an embodiment of the present invention.
FIG. 6 is an explanatory diagram of mathematical expressions that are arithmetically processed in a composite image output mode according to an embodiment of the present invention.
FIG. 7 is a pixel arrangement diagram according to another embodiment of the solid-state imaging device.
FIG. 8 is a diagram showing how the dynamic range changes.
FIG. 9 is a flowchart illustrating a processing procedure for selecting and determining a composite image output mode and a non-composite image output mode according to an embodiment of the present invention.
FIG. 10 is a flowchart showing a processing procedure according to another embodiment instead of the flowchart of FIG. 9;
FIG. 11 is a flowchart illustrating a processing procedure according to another embodiment instead of the flowchart of FIG. 10;
[Explanation of symbols]
1 pixel 2 low sensitivity pixel (sub pixel)
3 High sensitivity pixels (main pixels)
10 Lens 11 Solid-state imaging device 15 CPU
23 A / D converter 26 Digital signal processing unit 29 Recording medium 44 Image composition processing circuit

Claims (4)

A solid-state imaging device having a low-sensitivity pixel and a high-sensitivity pixel; an exposure time determination unit that determines whether or not an exposure time for shooting is equal to or greater than a predetermined threshold; and When it is determined that shooting is performed, image data read from the high-sensitivity pixel is output, and when the exposure time determination unit determines that shooting is performed with an exposure time that does not satisfy the predetermined threshold, A digital camera comprising control means for synthesizing and outputting image data read from the low-sensitivity pixels to image data read from high-sensitivity pixels. A solid-state imaging device having a low-sensitivity pixel and a high-sensitivity pixel; an exposure time determination unit that determines whether or not an exposure time for shooting is equal to or greater than a predetermined threshold; and When it is determined that shooting is performed, the image data read from the high-sensitivity pixel is output as RAW data, and the exposure time determination unit determines that shooting is performed with an exposure time less than the predetermined threshold The digital camera comprises control means for outputting the image data read from the high sensitivity pixel and the image data read from the low sensitivity pixel as RAW data. The control unit discards the image data read from the low-sensitivity pixel or reads the image data from the low-sensitivity pixel when the exposure time determination unit determines that shooting is performed with an exposure time equal to or greater than the predetermined threshold. The digital camera according to claim 1, wherein the digital camera is stopped. 4. The digital according to claim 1, further comprising a setting sensitivity determination unit that determines whether or not a sensitivity setting is equal to or higher than a predetermined sensitivity, instead of the exposure time determination unit. camera.

Images