WO2010146748A1 - 撮像装置 - Google Patents
撮像装置 Download PDFInfo
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- WO2010146748A1 WO2010146748A1 PCT/JP2010/001851 JP2010001851W WO2010146748A1 WO 2010146748 A1 WO2010146748 A1 WO 2010146748A1 JP 2010001851 W JP2010001851 W JP 2010001851W WO 2010146748 A1 WO2010146748 A1 WO 2010146748A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/741—Circuitry for compensating brightness variation in the scene by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
- H04N25/571—Control of the dynamic range involving a non-linear response
- H04N25/575—Control of the dynamic range involving a non-linear response with a response composed of multiple slopes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/76—Circuitry for compensating brightness variation in the scene by influencing the image signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
- H04N25/571—Control of the dynamic range involving a non-linear response
- H04N25/573—Control of the dynamic range involving a non-linear response the logarithmic type
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/68—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to defects
- H04N25/683—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to defects by defect estimation performed on the scene signal, e.g. real time or on the fly detection
Definitions
- the present invention relates to an image pickup apparatus including an image pickup element including a plurality of pixels having different photoelectric conversion characteristics at an inflection point.
- linear characteristics linear photoelectric conversion characteristics
- log characteristics logarithmic photoelectric conversion characteristics
- FIG. 5 is a graph showing the linear log characteristics, where the vertical axis indicates the pixel value and the horizontal axis indicates the luminance in logarithm.
- the photoelectric conversion characteristic of a certain pixel PX1 is indicated by a graph G1
- the photoelectric conversion characteristic of another certain pixel PX2 is indicated by a graph G2.
- the area indicated by D1 is a linear area having linear characteristics
- the area indicated by D2 is a log area having log characteristics.
- the pixel data read by the pixels having linear log characteristics is converted into linear characteristics or log characteristics by photoelectric conversion characteristics as preprocessing for performing various image processing by an image processing circuit provided on the output side of the image sensor. Processing to unify is performed.
- the pixel data belonging to the linear area D1 shown in FIG. 5 is subjected to various image processing with the same values, and the pixel data belonging to the log area D2 is converted to linear characteristics.
- Various image processing is performed with the obtained values.
- the inflection point (which may be described as an inflection point) P1 which is the start level of the log area D2, generally varies from pixel to pixel.
- the dynamic range DL1 when the dynamic range DL1 is set based on the pixel PX2 having a low pixel value at the inflection point P1, the pixel PX1 having a high pixel value at the inflection point P1 is set. In the photoelectric conversion characteristics, many saturated regions SD are generated on the high luminance side. Therefore, the dynamic range of the image sensor is determined based on a pixel having a high pixel value at the inflection point P1.
- the range of the dynamic range DL2 set based on the pixel PX1 having a high pixel value at the inflection point P1 is the dynamic range set based on the pixel PX2 having a low pixel value at the inflection point. It can be seen that it is much narrower than the range DL1.
- the dynamic range is set on the basis of the pixel PXn whose pixel value at the inflection point P1 is somewhat high, and a pixel with a pixel value at the inflection point P1 higher than the pixel PXn is defective. It was treated as a pixel.
- Patent Document 1 exists as a prior art related to the present application.
- a pixel having a high pixel value at the inflection point is regarded as a defective pixel, and interpolation processing using uniform neighboring pixels is performed regardless of the pixel value. Therefore, there has been a problem that the resolution of the image captured by the image sensor is lowered. Further, when a pixel having a low pixel value at the inflection point P1 is adopted as the pixel PXn in order to expand the dynamic range, the number of defective pixels increases, the number of pixels subjected to interpolation processing increases, and further resolution is increased. Will be reduced.
- An object of the present invention is to provide an imaging device capable of suppressing a decrease in resolution and simultaneously expanding a dynamic range.
- An imaging apparatus performs an imaging element including a plurality of pixels having different photoelectric conversion characteristics at an inflection point, and performs predetermined characteristic conversion processing on pixel data read by each pixel. And a characteristic converter that converts the photoelectric conversion characteristic of each pixel data into a predetermined reference photoelectric conversion characteristic, wherein the characteristic converter is an inflection of a target pixel that is one pixel among the plurality of pixels.
- the photoelectric conversion characteristics of the pixel data read by the target pixel are converted into the reference photoelectric conversion characteristics, and the target The pixel of the pixel of interest that has undergone the characteristic conversion process when the pixel value of the inflection point is equal to or less than the threshold value of the inflection point or the pixel value of pixel data read by the pixel of interest is equal to or less than the pixel threshold value
- the photoelectric conversion characteristic of the pixel data read by the target pixel is converted into the reference photoelectric conversion characteristic.
- FIG. 1 is a block diagram of an imaging apparatus according to Embodiment 1 of the present invention.
- FIG. 2 is a block diagram illustrating a detailed configuration of an image processing unit illustrated in FIG. 1. It is the schematic diagram which showed an example of the data structure of a lookup table. It is the graph which showed the photoelectric conversion characteristic of the pixel in which the pixel value of an inflection point exceeds an inflection point threshold value. It is the graph which showed the linear log characteristic.
- FIG. 1 shows a block diagram of an imaging apparatus according to Embodiment 1 of the present invention.
- the imaging apparatus is composed of a digital camera, and includes a lens unit 2, an imaging sensor 3 (an example of an imaging element), an amplifier 4, an A / D conversion unit 5, an image processing unit 6, an image memory 7, and a control.
- the lens unit 2 includes an optical lens system that captures an optical image of a subject and guides it to the image sensor 3.
- the optical lens system for example, a zoom lens, a focus lens, other fixed lens blocks, and the like arranged in series along the optical axis L of the optical image of the subject can be employed.
- the lens unit 2 includes a diaphragm (not shown) for adjusting the amount of transmitted light, a shutter (not shown), and the like, and the driving of the diaphragm and the shutter is controlled under the control of the control unit 8.
- the imaging sensor 3 includes a plurality of pixels arranged in a matrix of predetermined rows ⁇ predetermined columns and having different photoelectric conversion characteristics at an inflection point, and photoelectrically converts a light image formed in the lens unit 2.
- Image data composed of pixel values of R (red), G (green), and B (blue) color components having a level corresponding to the amount of light is generated and output to the amplifier 4.
- the image sensor 3 an image sensor such as a CMOS image sensor, a VMIS (Threshold Voltage Modulation Image Sensor) image sensor, or a CCD image sensor may be employed.
- an image sensor in which pixels of each color component are arranged in, for example, an RGB Bayer array is employed as the image sensor 3. That is, the imaging sensor 3 is an imaging sensor in which a plurality of types of pixels for reading pixel data having different color components are repeatedly arranged in a fixed pattern.
- the arrangement direction of the pixels in each row is the horizontal direction
- the arrangement direction of the pixels in each column is the vertical direction.
- the imaging sensor 3 sequentially outputs pixel data read by each pixel so as to perform raster scanning from the upper left pixel toward the lower right pixel, for example.
- each pixel has a low-luminance side photoelectric conversion characteristic as a linear characteristic, and a high-luminance side photoelectric conversion characteristic as a log characteristic. Further, as shown in FIG. 5, the boundary between the linear characteristic and the log characteristic is the inflection point P1. Further, the pixel value of the inflection point P1 is described as a bending start level S.
- the amplifier 4 includes, for example, an AGC (auto gain control) circuit and a CDS (correlated double sampling) circuit, and amplifies the image data output from the imaging sensor 3.
- the A / D converter 5 converts the R, G, and B color image data amplified by the amplifier 4 into R, G, and B digital image data.
- pixel data received by each pixel of the image sensor 3 is converted into pixel data having, for example, a 12-bit gradation value.
- the image processing unit 6 performs image processing as will be described later.
- the image memory 7 is composed of, for example, a RAM (Random Access Memory), and stores image data subjected to image processing by the image processing unit 6.
- the control unit 8 includes a ROM that stores various control programs, a RAM that temporarily stores data, a central processing unit (CPU) that reads and executes control programs from the ROM, and the like. To manage.
- the monitor unit 9 employs, for example, a color liquid crystal display disposed on the back surface of the housing of the imaging apparatus, and displays on the monitor an image taken by the imaging sensor 3 or an image stored in the image memory 7.
- the operation unit 10 includes various operation switch groups such as a power switch, a release switch, a mode setting switch for setting various shooting modes, and a menu selection switch.
- the release switch When the release switch is pressed, the subject is imaged by the imaging operation, that is, the imaging sensor 3, predetermined image processing is performed on the image data obtained by this imaging, and the image data is recorded in the image memory 7 or the like. A series of shooting operations are executed. Note that the image data is not stored in the image memory 7 or the like, but is output as a digital signal from the image processing unit 6, or is D / A converted and output as an analog signal such as NTSC. Also good.
- FIG. 2 is a block diagram showing a detailed configuration of the image processing unit 6 shown in FIG.
- the image processing unit 6 includes a black variation correction unit 61, a defect correction unit 62, a Bayer interpolation unit 63, a characteristic conversion unit 64, a gradation conversion unit 65, and a tone curve correction unit 66.
- the black variation correcting unit 61 corrects variations in the black level of each pixel constituting the imaging sensor 3.
- the defect correcting unit 62 performs an interpolation process for interpolating pixel data read by a defective pixel that can output only a pixel value equal to or less than a predetermined reference value, using pixel values of surrounding pixels.
- linear interpolation or spline interpolation can be adopted as the interpolation processing.
- the Bayer interpolation unit 63 executes Bayer interpolation, which is an interpolation process for interpolating missing pixels in each color component that occurs because the pixels constituting the image sensor 3 are in a Bayer array. As a result, image data representing one image is represented by three image data corresponding to the three color components R, G, and B. If the image sensor 3 is a monochrome image sensor, the Bayer interpolation unit 63 may be omitted.
- the characteristic conversion unit 64 includes an inflection point variation correction unit 641, an inflection point interpolation unit 642, and a memory unit 643, and converts the photoelectric conversion characteristics of each pixel data into predetermined reference photoelectric conversion characteristics. Since the Bayer interpolation unit 63 outputs three pieces of image data corresponding to the R, G, and B color components, the characteristic conversion unit 64 outputs each of the three pieces of image data corresponding to each color component. Then, the following processing is executed.
- the characteristic conversion unit 64 adopts a linear characteristic as the reference photoelectric conversion characteristic, and converts the log characteristic into the linear characteristic, thereby executing a unified process of the photoelectric conversion characteristic.
- the inflection point variation correcting unit 641 unifies the photoelectric conversion characteristics of each pixel data into linear characteristics by executing a predetermined characteristic conversion process on the pixel data read by each pixel.
- the inflection point variation correcting unit 641 compares the pixel value d of the pixel data read by each pixel with the value of the bending start level S predetermined for each pixel, thereby obtaining the pixel data. Determines whether the pixel data is linear characteristic pixel data or log characteristic pixel data. If the pixel data is linear characteristic pixel data, the pixel value d is directly output as the pixel value d ′, and the log characteristic pixel data is output. If it is, the characteristic conversion process is executed on the pixel value d, and the obtained pixel value d ′ is output.
- the inflection point variation correcting unit 641 determines that the pixel data is pixel data with linear characteristics, In the case of S ⁇ d, it is determined that the pixel data is log characteristic pixel data.
- the inflection point variation correcting unit 641 uses the look-up table T in which the correspondence when the pixel value of the log area D2 is converted to the pixel value of the linear characteristic is determined in advance to obtain the pixel data of the log characteristic. What is necessary is just to convert into a linear characteristic.
- the lookup table T is a lookup table common to all pixels.
- FIG. 3 is a schematic diagram showing an example of the data structure of the lookup table T.
- the look-up table T is composed of n (n is an integer) cells with addresses “0” to “n ⁇ 1”. Each address corresponds to a relative value of the pixel value d with respect to the bending start level S, that is, d ⁇ S. Each cell stores values d1 to dn after conversion when a value obtained by subtracting the bending start level S from the pixel value d in the log area D2 is converted into linear characteristics.
- the lookup table T stores values obtained by converting each pixel value d belonging to the log area D2 shown in FIG. 5 so as to be on the extension line L1 of the linear area D1.
- the inflection point variation correction unit 641 has a dS address that is a value obtained by subtracting the bending start level S from the pixel value d of the pixel data.
- the log characteristic is converted into a linear characteristic by outputting the value of the lookup table T stored in the above as a value after conversion.
- each address of the lookup table T is made to correspond to dS is because the variation of the bending start level S of each pixel is taken into consideration. That is, in the present embodiment, the photoelectric conversion characteristics of the log area D2 of each pixel are assumed to have substantially the same waveform although the bending start level S varies. Therefore, by making each address of the lookup table T correspond to dS instead of d, this lookup table T can be applied to all pixels.
- the inflection point variation correcting unit 641 can specify the pixel that has read the pixel data input from this order because the pixel data constituting one piece of image data is input in a predetermined order. Thereby, the bending start level S predetermined for each pixel can be specified.
- the inflection point interpolation unit 642 has a bending start level S of a pixel of interest, which is one pixel among a plurality of pixels, larger than a predetermined inflection point threshold and is read by the pixel of interest.
- the pixel value d of the pixel data is larger than the predetermined pixel threshold, the pixel data read by the neighboring pixel located in the vicinity of the target pixel is interpolated instead of the pixel value d ′ obtained by the above characteristic conversion processing.
- the photoelectric conversion characteristic of the pixel data read by the target pixel is converted into a linear characteristic.
- the inflection point interpolation unit 642 performs the inflection when the bending start level S of the target pixel is equal to or lower than the inflection point threshold value or the pixel value d of the pixel data read by the target pixel is equal to or lower than the predetermined pixel threshold value.
- the pixel value d ′ that has been subjected to the characteristic conversion processing by the point variation correcting unit 641 is directly output as the pixel value d ′′.
- the pixel value of the pixel data read by the pixel of interest is d (x, y), and the pixel whose characteristic conversion processing has been executed by the inflection point variation correction unit 641.
- the pixel value of the data is d ′ (x, y)
- the inflection point threshold value of the target pixel is Sth
- the pixel threshold value of the target pixel is Dth
- the inflection point interpolation unit 642 uses four pixels adjacent to the target pixel in the horizontal and vertical directions as neighboring pixels. Then, the average value of these four neighboring pixels is output as d ′′.
- the inflection point interpolation unit 642 may specify two pixels adjacent in the horizontal direction to the target pixel as neighboring pixels, and output an average value of the two neighboring pixels as d ′′.
- the process of the inflection point interpolation unit 642 is represented by the following algorithm.
- the Bayer interpolation unit 63 is provided in the previous stage of the characteristic conversion unit 64, but in the subsequent stage of the characteristic conversion unit 64, specifically, between the gradation conversion unit 65 and the tone curve correction unit 66. It may be provided.
- the process of the inflection point interpolation unit 642 is represented by the following algorithm.
- drb indicates a pixel value of pixel data read by a pixel (R pixel or B pixel) to which a red or blue filter is
- the inflection point interpolation unit 642 is a pixel to which a filter of the same color as the target pixel is attached, and four pixels located in the vicinity of the target pixel are set as neighboring pixels, and the average of these four neighboring pixels The value is output as d ′′.
- the target pixel is an R pixel
- four R pixels located near the R pixel in the horizontal direction and two R pixels located near the vertical direction are adjacent. It becomes a pixel.
- the target pixel is a B pixel
- the neighboring pixels are the same as in the case of an R pixel.
- the target pixel is a G pixel
- four G pixels adjacent to the G pixel on the upper right side, the lower right side, the upper left side, and the lower left side are neighboring pixels.
- the number of neighboring pixels is four as an example, and a pixel to which a filter of the same color as the pixel of interest is attached, and two pixels that are adjacent to the pixel of interest in the horizontal direction are adopted as neighboring pixels. Also good.
- the memory unit 643 is configured by a nonvolatile recording medium such as an EEPROM, for example, and stores a bending start level S predetermined for each pixel.
- the memory unit 643 stores an inflection point threshold value Sth, a pixel threshold value Dth, and a lookup table T.
- the bending start level S is a value unique to each pixel
- the inflection point threshold Sth and the pixel threshold Dth are values common to all pixels.
- FIG. 4 is a graph showing the photoelectric conversion characteristics of a pixel in which the pixel value of the inflection point P1 exceeds the inflection point threshold Sth, that is, a pixel in which the pixel value of the inflection point P1 is extremely high.
- the horizontal axis represents the luminance.
- a pixel with an extremely high inflection point P1 has a large saturation region SD on the high luminance side. Resulting in.
- the inflection point interpolation unit 642 performs characteristic conversion when the pixel value d of the pixel data read by the pixel having the bending start level S larger than the inflection point threshold Sth is larger than the pixel threshold Dth.
- the above-described interpolation process is performed instead of the process.
- the dynamic range of a pixel having an extremely high pixel value at the inflection point P1 can be expanded from DL1 to DL.
- the pixel value d of pixel data read by a pixel having an extremely high pixel value at the inflection point P1 is equal to or less than the pixel threshold value Dth
- the pixel data is converted into linear characteristics by characteristic conversion processing instead of interpolation processing. Has been. As a result, resolution reduction is prevented.
- a saturation level that is the maximum pixel value that defines the dynamic range DL may be adopted, but pixel data in the vicinity of the saturation level is not high in image reproducibility. It is preferable to use a slightly lower value.
- an average value of the bending start levels S of all the pixels constituting the image sensor 3 may be adopted, or the upper few% (for example, 10) of the distribution of the bending start levels S of all the pixels. %) May be adopted such that the bending start level S of the pixels exceeds the inflection point threshold Sth.
- the gradation conversion unit 65 performs histogram equalization processing, dynamic range compression processing, and the like on the pixel data output from the characteristic conversion unit 64.
- the histogram equalization process is a process for uniformly distributing the gray level distribution in the image. Thereby, the contrast of an image can be clarified.
- the dynamic range compression processing for example, the technique described in Masami Ogata “Image Dynamic Range Compression Technology”, Nihon Kogyo Shuppan, Image Lab, 2004, June issue can be employed.
- the tone curve correction unit 66 performs gamma correction on the image data output from the gradation conversion unit 65. Note that the pixel data output from the tone curve correction unit 66 is stored in the image memory 7 shown in FIG.
- the operation unit 10 receives an imaging command from the user, the image data captured by the imaging sensor 3 is amplified to a predetermined level by the amplifier 4 and A / D conversion is performed by the A / D conversion unit 5. Input to the image processing unit 6.
- the pixel data input to the image processing unit 6 is corrected in black level by the black variation correction unit 61, the defective pixel is interpolated by the defect correction unit 62, and Bayer interpolation is performed by the Bayer interpolation unit 63. This is input to the music point variation correction unit 641.
- the pixel data input to the inflection point variation correction unit 641 is converted into a linear characteristic by the photoelectric conversion characteristic and input to the inflection point interpolation unit 642.
- the inflection point interpolation unit 642 has a pixel value d of the target pixel, which is the pixel data output from the Bayer interpolation unit 63, and a bending start level S of the target pixel, where the bending start level S> the inflection point threshold Sth,
- the condition of pixel value d> pixel threshold Dth is satisfied, the above-described interpolation process using the pixel value d ′ of the neighboring pixel output from the inflection point variation correction unit 641 is executed, and the pixel value d ′′ is calculated. Calculate and output to the gradation conversion unit 65.
- the inflection point interpolation unit 642 has the pixel value d of the pixel of interest, which is the pixel data output from the Bayer interpolation unit 63, and the bending start level S of the pixel of interest when the bending start level S ⁇ the inflection point threshold Sth.
- the pixel value d ′ of the target pixel output from the inflection point variation correcting unit 641 is output as it is to the gradation converting unit 65 as the pixel value d ′′.
- the pixel data processed by the inflection point interpolation unit 642 is subjected to histogram equalization processing, dynamic range compression processing, and the like by the tone conversion unit 65, and gamma correction is performed by the tone curve correction unit 66 and stored in the image memory 7. Is done.
- the pixel value of the inflection point P1 of the target pixel is larger than the inflection point threshold Sth, and the pixel data read by the target pixel is larger than the pixel threshold Dth.
- the pixel data read by the target pixel is converted into linear characteristics by interpolation processing using the pixel data read by the neighboring pixels.
- pixel data whose pixel value is close to the saturation level is not preferably subjected to characteristic conversion processing as it is because an image is not accurately reproduced.
- the pixel whose dynamic range is narrow due to the high pixel value of the inflection point is the target pixel, and the pixel data read by the target pixel belongs to the saturated region or a region close thereto, the above interpolation is performed.
- the dynamic range of the target pixel can be expanded.
- Embodiment 2 Next, an imaging apparatus according to Embodiment 2 of the present invention will be described.
- the imaging apparatus according to the present embodiment is characterized in that the interpolation process is performed using pixels suitable for the interpolation process among the neighboring pixels of the first embodiment.
- the inflection point interpolation unit 642 shown in FIG. 2 is read by a pixel having a pixel value greater than the pixel threshold Dth and a bending start level S greater than the inflection point threshold Sth among neighboring pixels.
- the obtained pixel data is not used for the interpolation process.
- the inflection point interpolation unit 642 performs the following processing.
- the second line of the above algorithm shows that the bending start level S of the left neighboring pixel is the inflection point threshold value Sth or less and the pixel value d is the pixel threshold value Dth or less.
- the third line of the above algorithm indicates that the bending start level S of the right neighboring pixel is not more than the inflection point threshold value Sth and the pixel value d is not more than the pixel threshold value Dth.
- the characteristic conversion process is performed by the inflection point variation correcting unit 641 when the bending start level S is not more than the inflection point threshold Sth and the pixel value d is not more than the pixel threshold Dth only for the left neighboring pixel. It is shown that the interpolation process is performed using only the pixel data of the neighboring pixels on the left side for which.
- the 8th line of the above algorithm shows the characteristic conversion processing by the inflection point variation correcting unit 641 when the bending start level S is not more than the inflection point threshold value Sth and the pixel value d is not more than the pixel threshold value Dth only for the right neighboring pixel. It is shown that the interpolation process is performed using only the pixel data of the neighboring pixels on the right side where the above is performed.
- the twelfth line of the algorithm is the case where the condition of the first line of the algorithm is not satisfied, that is, the bending start level S of the target pixel is equal to or lower than the inflection point threshold Sth, or the pixel value d of the target pixel is the pixel threshold Dth
- the pixel data of the pixel of interest subjected to the characteristic conversion processing by the inflection point variation correcting unit 641 is output as it is.
- two pixels that are adjacent to the target pixel in the horizontal direction are set as neighboring pixels.
- the present invention is not limited to this. The present invention can be applied even when four pixels including two pixels are adopted as neighboring pixels.
- the inflection point interpolation unit 642 reads out pixel data read by a pixel having a bending start level S larger than the inflection point threshold Sth and a pixel value d larger than the pixel threshold Dth among the four neighboring pixels. Interpolation processing may be performed using other pixel data.
- the bending start level S of the neighboring pixel on the left side is larger than the inflection point threshold value Sth and the pixel value d is larger than the pixel threshold value Dth
- the bending start level S of the further left pixel is not more than the inflection point threshold value Sth
- the bending start level S of the left neighboring pixel is greater than the inflection point threshold Sth and the pixel value d is greater than the pixel threshold Dth
- the bending start level S is equal to or less than the inflection point threshold Sth and the pixel value d. If a pixel having a pixel threshold value Dth or less is searched toward the left side and a pixel satisfying this condition is found by searching up to a predetermined number of pixels, this pixel may be adopted as a neighboring pixel.
- the right pixel, the upper pixel, the lower pixel, the upper left pixel, the upper right pixel, the lower left pixel, and the lower right pixel are also neighboring pixels in the same manner as the left pixel. Can be searched.
- the imaging apparatus when a pixel having an extremely low pixel value at the inflection point P1 is set as a target pixel, interpolation processing is performed on pixel data read by the target pixel.
- the neighboring pixels having extremely low inflection points are not used for the interpolation process, and therefore the interpolation process can be performed with high accuracy.
- the characteristic conversion unit 64 converts the log characteristic into the linear characteristic is illustrated, but the present invention is not limited to this, and the linear characteristic may be converted into the log characteristic. .
- the characteristic conversion unit 64 converts the log characteristic into the linear characteristic.
- the present invention is not limited to this, and the log characteristic and the transient characteristics of the linear characteristic and the log characteristic are not limited thereto. The present invention can be applied even when the transient characteristic indicating the characteristic is converted into the linear characteristic.
- the inflection point between the linear characteristic and the transient characteristic may be adopted as the inflection point P1, or the inflection point between the transient characteristic and the log characteristic may be adopted as the inflection point P1.
- the characteristic converter 64 may convert the linear characteristic and the transient characteristic into a log characteristic.
- An imaging device performs a predetermined characteristic conversion process on an image sensor including a plurality of pixels having different photoelectric conversion characteristics at an inflection point and pixel data read by each pixel. And a characteristic conversion unit that converts the photoelectric conversion characteristic of each pixel data into a predetermined reference photoelectric conversion characteristic, and the characteristic conversion unit is a target pixel that is one pixel among the plurality of pixels.
- the photoelectric conversion characteristic of the pixel data read by the target pixel is converted into the reference photoelectric conversion characteristic, and the previous When the pixel value of the inflection point of the target pixel is equal to or less than the inflection point threshold value or the pixel value of pixel data read by the target pixel is equal to or less than the pixel threshold value, By outputting the pixel value as it is, the photoelectric conversion characteristic of the pixel data read by the target pixel is converted into the reference photoelectric conversion characteristic.
- the inflection point pixel values of neighboring pixels are rarely extremely high, and the dynamic range of neighboring pixels is Compared to the dynamic range, the possibility is wide. Further, pixel data whose pixel value is close to the saturation level is not preferably subjected to characteristic conversion processing as it is because an image is not accurately reproduced.
- the pixel whose dynamic range is narrow due to the high pixel value of the inflection point is the target pixel, and the pixel data read by the target pixel belongs to the saturated region or a region close thereto, the above interpolation is performed.
- the dynamic range of the target pixel can be expanded.
- the photoelectric conversion characteristic of the pixel data is The reference photoelectric conversion characteristic is converted by the characteristic conversion process instead of the interpolation process.
- the photoelectric conversion characteristic of the pixel data read by the pixel whose inflection point pixel value is equal to or less than the inflection point threshold value is converted into the reference photoelectric conversion characteristic by the characteristic conversion process.
- the characteristic conversion unit converts the pixel data read by the neighboring pixels into the reference photoelectric conversion characteristic by the characteristic conversion process, and reads the pixel data of the neighboring pixels after conversion by the pixel of interest. It is preferable to perform the interpolation processing on the obtained pixel data.
- the interpolation processing is performed using the pixel data after conversion into the reference photoelectric conversion characteristics.
- the characteristic conversion unit reads out pixel data read by a pixel having a pixel value larger than the pixel threshold value and an inflection point larger than the inflection point threshold among the neighboring pixels, to the interpolation process. It is preferable not to use it.
- the characteristic conversion unit specifies two pixels adjacent in the horizontal direction to the target pixel as the neighboring pixels.
- two pixels adjacent in the horizontal direction that is, two pixels adjacent to the same row are used as neighboring pixels, and therefore a memory for holding pixel data read by pixels in another row And the like, and the interpolation process can be executed without waiting for the pixel data to be read from the pixels in the other rows, so that the apparatus configuration can be simplified.
- the characteristic conversion unit specifies two pixels adjacent in the horizontal direction and two pixels adjacent in the vertical direction as the neighboring pixels with respect to the target pixel.
- the interpolation process since the interpolation process is performed using four neighboring pixels, the interpolation process can be executed with high accuracy.
- a plurality of types of pixels for reading pixel data having different color components are repeatedly arranged in a fixed pattern, and the characteristic conversion unit is in the vicinity of the target pixel of the same type as the target pixel. It is preferable that the pixel located at is specified as the neighboring pixel.
- interpolation processing can be executed using a pixel that reads pixel data of the same color as the target pixel as a neighboring pixel.
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Abstract
Description
図1は、本発明の実施の形態1による撮像装置のブロック図を示している。図1に示すように撮像装置は、デジタルカメラから構成され、レンズ部2、撮像センサ3(撮像素子の一例)、アンプ4、A/D変換部5、画像処理部6、画像メモリ7、制御部8、モニタ部9、及び操作部10を備えている。
d´´(x,y)=((d´(x-1,y)+d´(x+1,y)+d´(x,y-1)+d´(x,y+1))/4
else
d´´(x,y)=d´(x,y)
上記の例では、変曲点補間部642は、注目画素に対して水平及び垂直方向に隣接する4つの画素を近傍画素としている。そして、これら4つの近傍画素の平均値がd´´として出力される。
d´´(x,y)=((d´(x-1,y)+d´(x+1,y))/2
else
d´´(x,y)=d´(x,y)
図2では、ベイヤー補間部63は、特性変換部64の前段に設けられているが、特性変換部64の後段、具体的には、階調変換部65とトーンカーブ補正部66との間に設けてもよい。
drb´´(x,y)=((drb´(x-2,y)+drb´(x+2,y)+drb´(x,y-2)+drb´(x,y+2))/4
dg´´(x,y)=((dg´(x-1,y-1)+dg´(x+1,y-1)+dg´(x-1,y+1)+dg´(x+1,y+1))/4
else
drb´´(x,y)=drb´(x,y)
dg´´(x,y)=dg´(x,y)
但し、drbは、ベイヤー配列において、赤又は青のフィルターが取り付けられた画素(R画素又はB画素)により読み取られた画素データの画素値を示し、dgは、緑のフィルターが取り付けられた画素(G画素)により読み取られた画素データの画素値を示す。
次に、本発明の実施の形態2による撮像装置について説明する。本実施の形態の撮像装置は、実施の形態1の近傍画素の中から、補間処理に適した画素を用いて補間処理を行うことを特徴とする。
1: if(S(x,y)>Sth&d(x,y)>Dth){
2: if(S(x-1,y)≦Sth&d(x-1,y)≦Dth{
3: if(S(x+1,y)≦Sth&d(x+1,y)≦Dth
4: d´´(x,y)=(d´(x-1,y)+d´(x+1,y))/2
5: else
6: d´´(x,y)=d´(x-1,y)
7: }else{
8: if(S(x+1,y)≦Sth&d(x+1,y)≦Dth)
9: d´´(x,y)=((d´(x+1,y)
10: }
11:}else
12: d´´(x,y)=d´(x,y)
上記アルゴリズムの1行目は、注目画素の屈曲開始レベルSが変曲点閾値Sthより大きく、かつ、画素値dが画素閾値Dthより大きいことを示している。
Claims (6)
- 変曲点を境に異なる光電変換特性を有する複数の画素を備える撮像素子と、
各画素で読み取られた画素データに、所定の特性変換処理を実行することで、各画素データの光電変換特性を所定の基準光電変換特性に変換する特性変換部とを備え、
前記特性変換部は、
前記複数の画素のうち、ある1つの画素である注目画素の変曲点の画素値が所定の変曲点閾値より大きく、かつ、前記注目画素により読み取られた画素データの画素値が所定の画素閾値より大きい場合、前記特性変換処理に代えて、前記注目画素の近傍に位置する近傍画素により読み取られた画素データを用いた補間処理を行うことで、前記注目画素により読み取られた画素データの光電変換特性を前記基準光電変換特性に変換し、
前記注目画素の変曲点の画素値が前記変曲点閾値以下、又は前記注目画素により読み取られた画素データの画素値が前記画素閾値以下の場合、前記特性変換処理が実行された前記注目画素の画素値をそのまま出力することで、前記注目画素により読み取られた画素データの光電変換特性を前記基準光電変換特性に変換することを特徴とする撮像装置。 - 前記特性変換部は、前記近傍画素により読み取られた画素データを前記特性変換処理により前記基準光電変換特性に変換し、変換後の近傍画素の画素データを用いて、前記注目画素により読み取られた画素データに前記補間処理を実行することを特徴とする請求項1記載の撮像装置。
- 前記特性変換部は、前記近傍画素のうち、画素値が前記画素閾値より大きく、かつ、変曲点が前記変曲点閾値より大きい画素により読み取られた画素データは、前記補間処理に使用しないことを特徴とする請求項1又は2記載の撮像装置。
- 前記特性変換部は、前記注目画素に対して水平方向に隣接する2つの画素を前記近傍画素として特定することを特徴とする請求項1~3のいずれかに記載の撮像装置。
- 前記特性変換部は、前記注目画素に対して水平方向に隣接する2つの画素及び垂直方向に隣接する2つの画素を前記近傍画素として特定することを特徴とする請求項1~3のいずれかに記載の撮像装置。
- 前記撮像素子は、それぞれ色成分が異なる画素データを読み取るための複数種類の画素が一定のパターンで繰り返し配列され、
前記特性変換部は、前記注目画素と同一種類の前記注目画素の近傍に位置する画素を前記近傍画素として特定することを特徴とする請求項1~5のいずれかに記載の撮像装置。
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EP10789133.5A EP2445198A4 (en) | 2009-06-15 | 2010-03-16 | IMAGE CAPTURE APPARATUS |
US13/378,669 US20120092539A1 (en) | 2009-06-15 | 2010-03-16 | Image Pickup Apparatus |
JP2010524278A JP4586942B1 (ja) | 2009-06-15 | 2010-03-16 | 撮像装置 |
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JP2011024246A (ja) * | 2009-06-15 | 2011-02-03 | Konica Minolta Opto Inc | 撮像装置 |
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EP2445199A4 (en) * | 2009-06-15 | 2014-04-30 | Konica Minolta Opto Inc | IMAGE CAPTURE APPARATUS |
WO2012117616A1 (ja) * | 2011-02-28 | 2012-09-07 | 富士フイルム株式会社 | 撮像装置及び欠陥画素補正方法 |
WO2012150660A1 (ja) * | 2011-05-02 | 2012-11-08 | コニカミノルタアドバンストレイヤー株式会社 | 撮像装置 |
US9892487B1 (en) * | 2016-11-28 | 2018-02-13 | Sony Corporation | Method and apparatus for combining pixel values in array including linear pixels and logarithmic pixels |
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- 2010-03-16 JP JP2010524278A patent/JP4586942B1/ja not_active Expired - Fee Related
- 2010-03-16 EP EP10789133.5A patent/EP2445198A4/en not_active Withdrawn
- 2010-03-16 WO PCT/JP2010/001851 patent/WO2010146748A1/ja active Application Filing
- 2010-03-16 US US13/378,669 patent/US20120092539A1/en not_active Abandoned
- 2010-09-08 JP JP2010200539A patent/JP2011024246A/ja active Pending
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JPWO2010146748A1 (ja) | 2012-11-29 |
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US20120092539A1 (en) | 2012-04-19 |
EP2445198A4 (en) | 2014-05-14 |
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