JPH10294912A - Method and device for extending dynamic range of picture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the change of a density level natural without generating the pseudo contour of pictures by using an exposure coefficient and correcting the picture data of a different exposure to the picture data to be a reference. SOLUTION: In memories M1-M3, the picture data respectively image-picked up by an intermediate exposure, a large exposure and a small exposure are stored. When it is judged in a judgment circuit 16 that the picture data are present on the outside of the stipulated range of a dynamic range for the density level of the picture data stored in the memory M1, respective arithmetic units 17 and 18 use the picture data of the memory M1 and the picture data of the memories M2 and M3 and compute and obtain a density level difference and the exposure coefficient. The obtained density level and exposure coefficient are supplied to density conversion circuits 24 and 25, the density level on the outside of the stipulated range among the picture data stored in the memory M1 is converted the picture data after correction and the dynamic range is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for extending the dynamic range of an image, and detects not only an image but also a physical quantity, for example, an amplitude of an electric signal such as a voltage or current, and a physical quantity such as temperature and humidity. A method and apparatus for extending the dynamic range of a detector.

[0002]

To extend the dynamic range of the Prior Art Image is essential for image processing an outdoor scene, for example, by a camera, the order to image one of the subject including a sunlit and shade outdoors, 10 ³ to 10 Requires a dynamic range of ⁴ orders. However existing CCD (charge storage device) camera has a dynamic range of 10 ^2, it is impossible to obtain a clear image.

A typical prior art is disclosed in, for example,
As disclosed in JP-A-174470 and JP-A-6-105224, images having different exposure amounts depending on the aperture and shutter speed of a camera for imaging a subject or the charge storage time of a CCD (charge storage element) are simply fitted. It has a configuration to combine the data. As shown in FIG.
According to this prior art, when the horizontal axis sets the coordinates of the pixels in the horizontal direction of the image in which the subject is photographed, the exposure amount range P1 at an intermediate exposure amount and the exposure amount range P2 larger than that are set.
And an image obtained in a range P3 of an exposure amount smaller than the intermediate exposure amount has a characteristic L1 indicated in relation to the density level on the vertical axis.
To L3 are obtained. These characteristics L1 to L3
Depends on the amount of exposure and the characteristics of the camera.

[0004] In this prior art, there is a problem that pseudo contours 1 and 2 are generated due to a density difference between the images by fitting large and small exposure images into images with an intermediate exposure amount.

Another prior art is JP-A-7-131704, which is shown in FIG. 15 corresponding to FIG. 11 described above. In this prior art, it is assumed that camera characteristics when performing image synthesis, that is, a change characteristic of an exposure amount due to a diaphragm, a shutter speed, a transmittance of a filter and a lens, and a change characteristic of an output with respect to an incident light amount are known. Or by calculation, an area P1 in the middle of the exposure amount
The dynamic range is expanded by matching only the density levels of the region P2 with the large exposure amount and the region P3 with the small exposure amount. In this prior art, the exposure amount is not corrected.

Therefore, in this prior art, there are folds 3 in the characteristics L1 and L2, which are the gradients of the density levels in FIG. 15, due to errors in the camera characteristics or because the exposure amount is not corrected. This results in false contours and unnatural changes in density levels.

[0007] Still another prior art is disclosed in Japanese Patent Laid-Open No. 7-1317.
08, which is shown in connection with FIG. In this prior art, the exposure amount is corrected in an intermediate exposure region P1, a large exposure region P2, and a small exposure region P3, and the characteristics L1 to L3 in FIG. The exposure amount is corrected so as to be as follows. However, the correction of the density level in each of the regions P1, P2, and P3 is not performed.

Therefore, according to this prior art, an image having a different exposure amount is caused by noise and fluctuation of a black level (pedestal level) which is a reference potential at the time of analog / digital conversion of a video signal when a camera captures a subject. There is an offset between the digitized density values between them. Therefore, the offset causes density level differences 4 and 5, and in this prior art as well, false contours occur and density level changes become unnatural.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for extending a dynamic range in which a change in density level is natural without a false contour of an image.

Another object of the present invention is to extend the dynamic range of a detector capable of accurately extending the dynamic range of a detector for detecting physical quantities such as the amplitude, temperature, and humidity of an electric signal. To provide a method and apparatus.

[0011]

SUMMARY OF THE INVENTION According to the present invention, there is provided an image processing apparatus which obtains a single image data having an extended dynamic range from image data of a plurality of screens obtained by imaging the same subject with different exposure amounts. In the method of extending the dynamic range, of image data having different exposure amounts, the density level at both ends or one end of the dynamic range of the reference image data in the same subject portion is set to the density level of image data having different exposure amounts. Concentration level adjustment α
1, α2, and the change amount (Fb−Fa,
Fd-Fc), the exposure amount is determined for the reference image data using the exposure amount coefficients β2m and β1m, which are the ratios of the density level change amounts (F2b-F2a, F1d-F1c) of the image data having different exposure amounts. This is a method for extending the dynamic range of an image characterized by correcting different image data. Further, the present invention, as the image data based on the obtained image data of the extended dynamic range of a single sheet,
By repeating the above processing, it is possible to expand to a desired dynamic range. Further, according to the present invention, first image data captured with a certain exposure amount and second image data captured with a larger exposure amount than the first image data are obtained, and one of the dynamic ranges of the first image data is obtained. Density level F represented by edge image data
a and a density level difference α2 between the density level F2a represented by the image data at the other end of the dynamic range of the second image data, and the image data at the one end of the dynamic range represented by the first image data. A change amount (Fb-Fa) of the density level with respect to the subject portion is determined, and the change amount (F2b-F2a) of the density level with respect to the subject portion represented by the image data at the other end of the dynamic range in the second image data. Exposure coefficient β2m which is the ratio
And correcting the density level F2old of the second image data based on the density level difference α2 and the exposure coefficient β2m to obtain the corrected image data continuous to the one end of the dynamic range of the first image data. This is a method for expanding the dynamic range of an image, which is characterized by obtaining F2new. Further, according to the present invention, the density level F
2new is: F2new = Fa + (F2old + α2-Fa) × β
2 m 2. Further, according to the present invention, the first image data obtained at a certain exposure amount and the second image data taken at an exposure amount smaller than the first image data are obtained. Density level F represented by edge image data
d, and a density level difference α1 between the density level F1d represented by the image data at the other end of the dynamic range of the second image data is obtained, and the image data at the one end of the dynamic range is represented by the first image data. A change amount (Fc-Fd) of the density level with respect to the subject portion is obtained, and the change amount of the density level (F1d-F1c) of the second image data with respect to the subject portion represented by the image data at the other end of the dynamic range is obtained. Exposure coefficient β1m which is the ratio
And correcting the density level F1old of the second image data based on the density level difference α1 and the exposure amount coefficient β1m to obtain the corrected image data continuous to the one end of the dynamic range of the first image data. This is a method for expanding the dynamic range of an image, which is characterized by obtaining F1new. Further, according to the present invention, the density level F
1new is: F1new = Fd + (F1old + α1-Fd) × β
1 m 2. According to the present invention, a plurality of (for example, three) screen image data obtained by imaging the same subject with mutually different exposure amounts are used to synthesize a plurality of images having different exposure amounts.
An image with an extended dynamic range in which both the density level and the exposure amount ratio are corrected can be obtained. Using the image data for the plurality of screens, the density level is adjusted, the ratio of the amount of exposure is determined from the image data for the plurality of screens, and the density conversion is performed using the ratios. In obtaining the density level α2, for example, one side of the dynamic range of the first image data with an intermediate exposure amount (that is, the brightness or illuminance of the subject is low, that is, the region which is dark and is imaged with a large exposure amount) And the density level represented by the image data on the other side of the dynamic range (that is, on the side of the area obtained with the intermediate exposure amount) of the second image data captured with the large exposure amount. It is obtained by calculating the difference from F2a. The exposure coefficient β2m, which is the ratio of the exposure, is based on, for example, the image data that is closer to one side of the dynamic range in the first image data, and the amount of change (Fb−
Fa) is obtained, and the dynamic range of the second image data for the same two object portions is changed based on the image data on the other side (F2b−
F2a). In this way, the levels of the first and second image data are adjusted, and the first and second image data are adjusted.
The image data on the one side of the dynamic range in the image data is converted to the density level F2ol of the second image data.
Compensation is performed by correcting d, and furthermore, by this calculation, the dynamic range can be further extended near the one side of the dynamic range of the first image data. In the above description and the following description, description will be made mainly in relation to image data having an intermediate exposure amount and image data having a large exposure amount. The same applies to image data with a small exposure amount. That is, in obtaining the density level α1, for example, of the first image data with the intermediate exposure amount, the one of the dynamic ranges is shifted toward one side (that is, the brightness or illuminance of the subject is high, that is, the region side where the image is captured with a small exposure amount is bright. ) And the density represented by the image data on the other side of the dynamic range (that is, the area obtained with the intermediate exposure amount) of the second image data captured with the small exposure amount. It is obtained by calculating the difference from the level F1d. Further, the exposure coefficient β1m, which is the ratio of the exposure, is based on, for example, the image data that is closer to one side of the dynamic range in the first image data, and the amount of change (Fd−
Fc), and the change amount (F1d-) of the density range based on the image data on the other side of the dynamic range of the second image data for the same two subject portions.
F1c). In this way, the levels of the first and second image data are adjusted, and the first and second image data are adjusted.
The image data on the one side of the dynamic range in the image data is converted to the density level F1ol of the second image data.
The d is corrected, calculated and replaced, and the calculation further extends the dynamic range closer to the one side of the dynamic range of the first image data.

In the present invention, the density levels F2new and F1new of the corrected image data are expressed as follows: F2new = Fa + (F2old + α2-Fa) × β
2m, and F1new = Fd + (F1old + α1-Fd) × β
1 m 2. According to the present invention, the density level F2ol of the second image data
d, F1old, and the corrected density level F2n of the second image data to be synthesized with the first image data using the density level difference α2 and the exposure coefficient β2m, β1m described above.
ew, F1new can be obtained. The image data may be monochrome, for example, but may also be color image data for each of red R, green G, and blue B.

Further, according to the present invention, the image data includes red R, green G
And image data for color for each color of blue B. Exposure coefficient β2m, β1m are exposure coefficient β2R, β2G, β2B; β1R, β2R obtained from image data for each color.
It is characterized by the average value of β1G and β1B. According to the present invention, when the first and second image data are color image data, the exposure coefficient β2m, β1m is
Individual exposure coefficient β2R, β2G, β2B obtained from image data for each color R, G, B; β1R, β1
G, β1B are average values. On the other hand, the density level differences α2, α1 are obtained by using independent values α2R, α2G, α2B for the respective colors R, G, B; Density level F2n of corrected image data for each color
ew and F1new are calculated and obtained. As a result, even when the sensitivity difference and the amplification factor of the image sensor for each color R, G, and B vary, the color reproducibility is excellent, and the black level difference between the colors R, G, and B is reduced. Less impact,
As a result, it is possible to prevent a pseudo contour from being generated.

Further, according to the present invention, the corrected image data F2new and F1new for each color are used as image data F2o used for obtaining the corrected image data F2new.
When ld is the image data with the larger exposure, the red gain is reduced compared to the blue gain to correct the color temperature,
When the image data F1old used for obtaining the corrected image data F1new is image data with a smaller exposure amount, the blue temperature is reduced compared to the red gain to correct the color temperature. And According to the present invention, the density level F2 of the corrected image data
New, F1 new color temperature correction is performed. When the subject is dark, the aperture diameter is increased, and the second image data in which the charge accumulation time is lengthened and the exposure amount is increased is used, the color temperature of the second image data is low.
The red gain is reduced and corrected compared to the blue gain. Conversely, for a bright subject, the exposure is adjusted to be small. In this case, the color temperature of the second image data is high, so that the blue gain is lower than the red gain.

According to the present invention, there is provided a method for storing first image data having a plurality of density levels imaged at a certain exposure amount.
A memory, a second memory for storing second image data having a plurality of density levels obtained by imaging the same subject as the first image data with an exposure amount larger than the exposure amount of the first image data, and a first memory; Of the plurality of predetermined density levels Fa and Fb on the side corresponding to the larger exposure amount within the dynamic range of the density level of the first image data stored in Extracting a coordinate of a pixel of the first memory having a certain density level Fa, a density level further outward, and a density level of a density level Fb which is inside the predetermined outward density level Fa; (1) extracting means, second extracting means for extracting a pixel of the second memory having the same coordinates as the coordinates extracted by the first extracting means, and an output of the second extracting means. In response to each of the predetermined density levels Fa and Fb, the average value calculation means for obtaining the average values F2a and F2b of the density levels of the pixels extracted from the second memory, and the output of the average value calculation means. And a density level difference α relating to a density level Fa outside the dynamic range for adjusting the density level of the second image data to the density level of the first image data.
2, α2 = Fa−F2a, and further, exposure coefficient β2m, β2m = (Fb−Fa) / (F2b), which is the ratio of the gradient of the density level of the first image data to the gradient of the density level of the second image data. -F2a), and in response to the output of the second extracting means, the predetermined density levels Fa, Fb in the first memory.
When the density level of a pixel in the second memory having the same coordinates as the coordinates of each pixel having a density level further outside the dynamic range is F2old, the density levels F2new, F2new = Fa + of the corrected image data. (F2old + α2-Fa) × β
And a second calculating means for calculating 2m 2. The present invention also provides a first memory for storing first image data having a plurality of density levels imaged at a certain exposure amount, and a first memory for storing the first image data having a smaller exposure amount than the first image data.
A second memory for storing second image data having a plurality of density levels obtained by imaging the same subject as the image data;
Within the dynamic range of the density level of the first image data stored in the memory, a plurality of predetermined density levels Fd, F on the side corresponding to the smaller exposure amount.
c, a density level Fd outside the dynamic range, a density level further outside the dynamic range, and a density level Fc inside the predetermined outside density level Fd. First extracting means for extracting the coordinates of the pixels of the first memory, second extracting means for extracting the pixels of the second memory having the same coordinates as the coordinates extracted by the first extracting means, and output of the second extracting means Means for calculating average values F1d and F1c of the density levels of the pixels extracted from the second memory for each of the predetermined density levels Fd and Fc, and responding to the output of the average value calculation means. Then, the density level of the second image data is related to the density level Fd located outside the dynamic range for adjusting the density level to the density level of the first image data. And the exposure coefficient β1m, β1m = (Fd-Fc), which is the ratio of the gradient of the density level of the first image data to the gradient of the density level of the second image data. ) / (F1d-F1c), and responding to the output of the second extracting means, the predetermined density levels Fd, Fc of the first memory are stored.
When the density level of a pixel in the second memory having the same coordinates as the coordinates of each pixel having a density level further outside the dynamic range is F1old, the density levels F1new, F1new = Fd + of the image data after correction. (F1old + α1-Fd) × β
And a second calculating means for calculating 1m 2. According to the present invention, for example, the side corresponding to one of the exposure amounts in the first image data stored in the first memory obtained by imaging with the intermediate exposure amount, for example, the larger amount, by the first extracting unit. The coordinates of the pixels of the first memory having a plurality of, for example, two predetermined density levels Fa and Fb on the side of the second image data picked up by the exposure amount are extracted, and the second extracting means extracts the pixels of the first memory. Pixels of the second memory having the same coordinates as the extracted coordinates, in other words, in the same subject portion are extracted by the second extracting means, and pixels of the second memory having the coordinates obtained by the second extracting means are extracted. The average level F2a, F2b is obtained by obtaining the density level of the image. The density level difference α2 is obtained based on the average value F2a corresponding to the density level Fa located outside the dynamic range. Average values F2a and F2b respectively corresponding to the density level Fa closer to the outside and the density level Fb located further inside.
Is used to determine the exposure coefficient β2m. By using the average values F2a and F2b in this manner, the accuracy of the density level difference α2 and the exposure coefficient β2m can be improved, and errors due to differences in exposure can be reduced.

Further, according to the present invention, the first and second image data are color image data for each of red R, green G and blue B, and the first arithmetic means includes a first and second image data for each color. Exposure coefficient β2R, β2 for each color based on image data
G, β2B; β1R, β1G, β1B are obtained, and the exposure coefficient β2R, β2G, β2B for each color is obtained.
It is characterized in that the average values β2m and β1m of G and β1B are obtained and given to the second calculating means. According to the present invention, the first and second image data are color image data for each color. In this case, the exposure coefficients β2m and β1m used for obtaining the density levels F2new and F1new of the corrected image data are , Exposure coefficient β2R, β2G, β2B obtained for each color; β1R,
The average value of β1G and β1B is used. With this, each color R,
Even if the sensor sensitivity and the amplification factor for each of G and B vary, the color reproducibility is excellent, the influence of the black level difference between each of the colors R, G and B is reduced, and the pseudo contour is prevented from being generated. be able to. The density level difference α2 is determined for each color R, G,
For each B, the density level F2new,
Used to determine F1new.

Further, according to the present invention, the first extracting means includes: (a) means for creating a histogram representing the number of pixels for each density level of the first image data stored in the first memory;
(B) In response to the output of the histogram creating means, one of the predetermined density levels Fa and Fb; Fd and Fc is more dynamic than the other predetermined density levels Fb and Fc. A predetermined density level F which is set outside of the range and is the other predetermined density level F
b and Fc are replaced with the one of the predetermined concentration levels Fa and F.
means for determining as an initial density level having a density level greater than or equal to a predetermined number of pixels within a dynamic range from d. According to the present invention, the one density level Fa, Fd in the first image data is used to determine the one density level Fa, Fd.
A specified range that is closer to the inside of the dynamic range than Fd is set.
The density level closer to d is set to the other predetermined density level F.
Defined as b, Fc. Thus, the exposure coefficient β2
m and β1m can be calculated and calculated with high accuracy.

Further, according to the present invention, (a) the first and second image data are color image data for each of red R, green G and blue B, and (b) the exposure amount of the first image data When the exposure amount of the second image data is large, the red gain is set to be lower than the blue gain, and when the exposure amount of the second image data is small, the blue gain is compared with the red gain. And (c) a color temperature correction calculating means for multiplying the gain stored in the color temperature correction memory by the corrected image data F2new and F1new. Features. According to the present invention, when the first and second image data are color image data, the color temperature correction is performed as described above, and the difference in the exposure amount between a bright part and a dark part in one subject is calculated. Correct the resulting color temperature difference.

According to the present invention, there is provided a method for storing first image data having a plurality of density levels imaged at a certain exposure amount.
A memory, a second memory storing second image data having a plurality of density levels obtained by imaging the same subject as the first image data with an exposure amount larger than the exposure amount of the first image data, and a first image data The exposure amount smaller than the exposure amount
A third memory for storing third image data having a plurality of density levels obtained by imaging the same subject as the image data;
Within the dynamic range of the density level of the first image data stored in the memory, the density level of the first image data is set to a predetermined first density level Fa on one side corresponding to the larger exposure amount, and It is outside the specified range between the second density level Fd and the second density level Fd on the other side corresponding to the smaller quantity, and is outside the first density level Fa, or is outside the second density level Fd. Determination means for determining whether the first image data is also outside, and the density level of the first image data is changed to the first density level Fa
When the third density level Fb is outside the first density level Fa, the third density level Fb is determined on the one side of the dynamic range to be inside the first density level Fa. First with level
First extracting means for extracting the coordinates of the pixels of the first image data stored in the memory, and second extracting means for extracting the pixels of the second memory having the same coordinates as the coordinates extracted by the first extracting means; , In response to the output of the second extracting means, for each of the first and third density levels Fa and Fb, the average value F2a, of the density levels of the pixels extracted from the second memory.
A first average value calculating means for calculating F2b, and a density level of the second image data in response to an output of the first average value calculating means,
A density level difference α2, α2 = Fa−F2a relating to the first density level Fa located outside the dynamic range for adjusting the density level to the density level of the first image data is obtained. The first calculation means for calculating the exposure coefficient β2m, β2m = (Fb−Fa) / (F2b−F2a), which is the ratio of the gradient of the density level of the first image data to the gradient of the level, and the output of the second extraction means. In response, when the density level of a pixel in the second memory having the same coordinates as the coordinates of each pixel having a lower density than the first density level Fa in the first memory is F2old, the density levels F2new, F2new of the image data after correction are given. Fa + (F2old + α2-Fa) × β
2m, and the density level of the first image data is changed to the second density level Fd in response to the output of the range determining means.
When it is more outward than the second density level, a fourth density level Fc that is inside the dynamic range from the second density level Fd is determined on the other side of the dynamic range, and the density level is equal to or higher than the second density level Fd and the fourth density level Fc. Third extracting means for extracting the coordinates of the pixels stored in the first memory having: and fourth extracting means for extracting the pixels of the third memory having the same coordinates as the coordinates extracted by the third extracting means; Second average value calculating means for responding to the output of the fourth extracting means for obtaining, for each of the second and fourth density levels Fd, Fc, average values F1d, F1c of the density levels of the pixels extracted from the third memory; Responsive to the output of the second average value calculating means, the density level of the third image data is shifted toward the outside of the dynamic range for adjusting the density level to the density level of the first image data. A density level difference α1, α1 = Fd−F1d with respect to the second density level Fd is obtained, and an exposure coefficient β1m, which is a ratio of a gradient of the density level of the first image data to a gradient of the density level of the third image data, β3m = (Fd−Fc) / (F1d−F1c), and the coordinates of each pixel having a density level exceeding the second density level Fd of the first memory in response to the output of the fourth extraction means. When the density level of the pixel in the third memory having the same coordinates as F1old is F1old, the density level F1new of the corrected image data, F1new = Fd + (F1old + α1-Fd) × β
And a fourth calculating means for calculating 1m 2. According to the present invention, the first image data is image data obtained by imaging with an intermediate exposure amount, the second image data is image data obtained by imaging with a large exposure amount,
The image data is image data obtained by capturing an image with a small exposure amount. With this, the dynamic range on both sides of the first image data is adjusted by adjusting the density level and making the exposure amount ratio coincide with each other, thereby reducing the dynamic range. It can be spread both up and down.

Further, according to the present invention, the same physical quantity to be measured is measured with mutually different characteristics, a plurality of pieces of detection data are obtained at the same time for each measurement, and both ends or one end of the dynamic range of the reference detection data are detected. Level, detection level of detection data measured with different characteristics and detection level matching α
1, α2, and the amount of change in the detection level (F2b) with respect to the amount of change (Fb-Fa, Fd-Fc) of the physical quantity to be measured between the reference data for the same object to be measured and the detection data measured with different characteristics. -F2a, F1d-
This is a method of extending the dynamic range of the detector, wherein the detection data measured with different characteristics from the reference detection data is corrected using the coefficients β2m and β1m which are the ratios of F1c). The present invention also provides a first memory for storing first detection data obtained by detecting a physical quantity to be measured with a predetermined characteristic, and a detection level of the first detection data based on the first characteristic by measuring the physical quantity to be measured within a low value range. The second to obtain with a detection level greater than
A second memory for storing second detection data obtained by detecting the physical quantity to be measured at the same time as the first detection data by a characteristic; and a dynamic range of a detection level of the first detection data stored in the first memory. , A plurality of predetermined detection levels Fa,
Fb having a detection level Fa outside the dynamic range, a detection level further outside the dynamic range, and a detection level Fb inside the predetermined outside detection level Fa. A first extracting means for extracting a time on the time axis of one memory; and a second extracting means for extracting a time at the same time as the time extracted by the first extracting means.
A second extraction means for extracting the detection data from the memory; and a dynamic range for adjusting the detection level of the second detection data to the detection level of the first detection data in response to an output of the second extraction means. The detection level difference α2, α2 = Fa−F2a with respect to the detection level Fa closer to the outside is obtained, and a coefficient β2m, which is a ratio of the slope of the detection level of the first detection data to the slope of the detection level of the second detection data, β2m = (Fb−Fa) / (F2b−F2a), and the predetermined detection levels Fa and Fb of the first memory in response to the output of the second extraction means.
When the detection level of the second memory at each same time having a detection level further outside than that is F2old,
Detection level F2new of the corrected detection data, F2new = Fa + (F2old + α2-Fa) × β2
and a second calculating means for calculating m. 2 is a device for extending the dynamic range of the detector. Further, the present invention provides a first memory for storing first detection data obtained by detecting a physical quantity to be measured with a predetermined characteristic, and a detection level of the first detection data based on the first characteristic by measuring the physical quantity to be measured within a high value range. The second to obtain with a detection level greater than
A second memory for storing second detection data obtained by detecting the physical quantity to be measured at the same time as the first detection data by a characteristic; and a dynamic range of a detection level of the first detection data stored in the first memory. , A plurality of predetermined detection levels Fd,
Among the Fc, a detection level having a detection level Fd located outside of the dynamic range, a detection level further located further outside, and a detection level of a detection level Fc located inside the predetermined detection level Fd located outside. A first extracting means for extracting a time on the time axis of one memory; and a second extracting means for extracting a time at the same time as the time extracted by the first extracting means.
A second extraction means for extracting the detection data from the memory; and a dynamic range for adjusting the detection level of the second detection data to the detection level of the first detection data in response to an output of the second extraction means. The detection level difference α1, α1 = Fd−F1d with respect to the detection level Fd on the outer side is obtained, and a coefficient β1m, which is a ratio of the inclination of the detection level of the first detection data to the inclination of the detection level of the second detection data, β1m = (Fd−Fc) / (F1d−F1c), and the predetermined detection levels Fd and Fc of the first memory in response to the output of the second extraction means.
When the detection level of the second memory at each same time having a detection level further outside than the above is F1old,
Detection level F1new of the corrected detection data, F1new = Fd + (F1old + α1-Fd) × β1
and a second calculating means for calculating m. 2 is a device for extending the dynamic range of the detector. ADVANTAGE OF THE INVENTION According to this invention, the dynamic range of the detector which measures the physical quantity to be measured which changes with time progress, such as the amplitude of electric signal voltage or electric current, temperature, and humidity, can be extended. The invention can thus be implemented not only in connection with images, but also widely in connection with detectors for measuring other physical quantities to be measured.

[0021]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention. The same subject is imaged with different exposure amounts by the camera 7 serving as an imaging means, and image data for a plurality of screens is obtained. This image data is color image data, and includes image data for each of red R, green G, and blue B. Image data of each color R, G, B from the camera 7 is digitized in an analog / digital conversion circuit 8 and converted into an 8-bit digital signal for each pixel of each color R, G, B. The digitized image data from the analog / digital conversion circuit 8 is supplied to the dynamic range expansion device 9 of the present invention, where the density level adjustment is performed for a plurality of digitized images having different exposure amounts. As well as
A screen composed of image data for each of the colors R, G, B is synthesized while correcting the exposure coefficient β2m, β1m described later.

Thus, the dynamic range is extended. The image data expanded by the dynamic range expansion device 9 can be given to an image processing device to perform color analysis and the like. The image data with the extended dynamic range is also given to the dynamic range compression device 10 for each color R, G, B synthesis, and the dynamic range extended image of the synthesized image is converted into, for example, a color cathode ray tube for displaying. Alternatively, the dynamic range is compressed so as to be provided to an output device such as a liquid crystal display.

The camera 7 includes a condenser lens 12 for forming an image of a subject on an image sensor 11. Image sensor 11
Is composed of, for example, a CCD (charge storage element), and a total of three pixels for each color R, G, B constitute one combination, and a large number of such combinations are arranged in a matrix. Each pixel is provided with a filter 13 of colors R, G, and B. In order to set the exposure amount, an exposure amount setting unit 14 including an aperture and a shutter is provided, and the charge accumulation time of the image sensor 11 is adjusted. Image sensor 11
The image data of each pixel is supplied to the analog / digital conversion circuit 8 and digitized as described above.

FIG. 2 is a block diagram showing the configuration of the dynamic range extending device 9. The digitized image data from the analog / digital conversion circuit 8 is input for each of the colors R, G, and B, and stored in the memories M1 to M3 for each screen.
, Through an image switching circuit 15. Memory M1
Stores image data of one screen imaged by an intermediate exposure amount. Image data captured with a large exposure amount is stored in the memory M2. Image data captured with a small exposure amount is stored in the memory M3. In FIG. 2, a solid line represents image data for each of the colors R, G, and B, and a broken line represents a control signal other than the image data. The density level of the image data having an intermediate exposure amount stored in the memory M1 is defined by a predetermined density level Fa closer to the darker side of the dynamic range and another predetermined density level Fd closer to the lighter side of the dynamic range. The determination circuit 16 determines whether image data exists outside the range. Memory M out of specified range
When at least a part of the image data stored in No. 1 exists, the arithmetic units 17 and 18 determine the density level difference α
2, α1 are calculated by the arithmetic circuits 19 and 20, and the exposure coefficients β2m and β1m are calculated by the arithmetic circuits 21 and 22.

If all the image data stored in the memory M1 is within the specified range, the image data is
Without being subjected to the calculation, the signal is directly passed to the image processing device through the replacement circuit 23 and is also supplied to the dynamic range compression device 10. When it is determined by the determination circuit 16 that the image data exists outside the specified range, each of the arithmetic units 17 and 18 performs the above-described calculation using the image data of the memory M1 and the image data of the memories M2 and M3. . The density level differences α2, α1 and the exposure coefficient β2m, β1 obtained by the arithmetic circuits 17 and 18 in this manner.
m is supplied to the density conversion circuits 24 and 25 and stored in the memory M1.
In the image data stored in the image data, the density level of a pixel having a density level outside the specified range is converted into corrected image data to extend the dynamic range.
The new corrected image data thus obtained is subjected to a correction operation in the color temperature correction circuits 26 and 27, and the replacement circuit 23
Given to. Therefore, image data within the specified range
The image data stored in the memory M1 is used as it is.
The image data is replaced with the image data given by the image data 6, 27, and the image data in which the dynamic range of one screen is extended is derived.

FIG. 3 is a diagram showing the relationship between the dynamic range of image data from the camera 7 and the density level of output image data when the exposure amount is changed. The horizontal axis in FIG.
The coordinates of the pixel in the horizontal direction of the subject are shown. This subject is configured for the sake of convenience such that the brightness or illuminance of the subject increases in the horizontal direction from left to right and becomes brighter, and the vertical axis in FIG. The scale is graduated from dark to light. The vertical axis in FIG. 3 represents the density level of the image data for each of the colors R, G, and B, and the reference symbol DR indicates the dynamic range of the camera 7. Image data captured with an intermediate exposure has the characteristic indicated by L4, and image data captured with a large exposure has the characteristic indicated by line L5, and an image captured with a smaller exposure. The data has the characteristics shown by line L6. Even if the brightness of the subject is the same, the density level of the image data differs depending on the value of the exposure amount,
It can also be seen that the gradient of the density level is different.

FIG. 4 is a diagram for explaining a subject. FIG. 4A shows a subject. As described above, the subject is configured such that the luminance or illuminance changes smoothly from dark to bright as going from left to right in the horizontal direction. In the vertical direction of the subject in FIG. 4A, the brightness of the subject is the same. FIG. 4B shows the brightness corresponding to the coordinates of the horizontal pixel of the subject shown in FIG. FIG.
The mutual interval Δb1 between the vertical lines in (1) corresponds to the brightness of the subject, and indicates that the brightness increases as Δb1 increases.

FIG. 5 is a diagram for explaining the operation when the camera 7 captures an image with an intermediate exposure amount, and FIG. 6 is a diagram for explaining the operation when the camera 7 captures an image with a large exposure amount. FIG. 7 is a diagram for explaining an operation when an image is captured by the camera 7 with a small exposure amount. Among these exposure conditions, image data of the subject obtained by large and small is shown in FIG. 5A, FIG. 6A and FIG. 7A, and the above-mentioned memories M1, M2, M3 , FIG. 5 (2), FIG. 6 (2) and FIG. 7 (2) are stored.

Referring to FIG. 5 (2), in the memory M1, the density levels obtained by the camera 7 at the coordinates A and D of the horizontal pixel coordinates of the subject indicated by the horizontal axis are indicated by reference numerals Fa and Fd. And the concentration levels Fa to
Fd is set within the above-mentioned specified range. The density level of the dynamic range DR is, for example, in this embodiment,
A total of 256 gradations from 0 to 255 are set. If the density level is outside the specified range below Fa and beyond Fd, according to the present invention, the memory M2 uses the image data captured under the condition of the large exposure amount in FIG. Each correction is made using image data captured under the condition that the exposure amount shown in (2) is small. The interval Δb2 between the vertical lines in FIGS. 5 (1), 6 (1) and 7 (1) indicates the density level, and the greater the interval Δb2, the greater the density level, that is, the brighter.

The memory M1 stores density levels f1 to fr corresponding to pixel coordinates (x1, y1) to (xm, yn) for each of the colors R, G, and B. The same applies to M2 and M3.

[0031]

[Table 1]

FIG. 8 is a histogram obtained according to the present invention for image data of one color, for example, red R in the memory M1. The horizontal axis in FIG. 8 indicates the density level, and the vertical axis in FIG. 8 indicates the number of pixels, that is, the frequency.

FIG. 9 is a block diagram showing a simplified operation of the entire dynamic range extending device 9 shown in FIG. The dynamic range expansion device 9 performs a first operation 28 on the image data stored in the memory M1, performs a second operation 29 on the image data stored in the memory M2, and stores the image data in the memory M3. A third operation 30 is performed on the image data that has been set. Specific steps a1 to a9 of these first to third operations 28 to 30; a10 to a17; a20 to a
27 is shown in FIGS. 10 to 12, respectively.

In the exposure amount imaged by the camera 7,
The large and small image data are stored in the memory M as described above.
1, M2, and M3. First, the image data of the memory M1 is read out for each of the colors R, G, and B in step a1, and it is determined in step a2 whether the image data is within the specified range of the density level Fa or more and the density level Fd or less. The determination is performed by the determination circuit 16.
If it is determined that all the image data in the memory M1 exists within the specified range Fa to Fd and does not exist outside the specified range, the operation is terminated without performing the dynamic range expansion operation in step a3. .

If it is determined in step a4 that at least a part of the image data in the memory M1 is out of the specified range, in step a5, the image data outside the specified range is classified into cases 1-3. . In case 1, at least a part of the image data of the memory M1 is
This is the case where Fd exceeds the upper limit Fd. Case 2
The case where at least a part of the image data in the memory M1 exists below the lower limit density level Fa. Case 3
Is the case where both the cases 1 and 2 described above are satisfied, that is, at least a part of the image data in the memory M1 exists beyond the density level Fd, and the density level F
This is the case when the value is less than a.

In step a6, the histogram described with reference to FIG. 8 is created for the image data in the memory M1. This histogram represents a frequency which is the number of pixels for each density level of the image data in the memory M1.

In step a7, for the image data in the memory M1, in case 1 or case 3, the density level Fc which is equal to or lower than the upper limit density level Fd of the specified range and equal to or higher than the predetermined specified frequency Q is converted into the histogram. Search using That is, Fc is defined as the first density level having a density level equal to or larger than the predetermined number of pixels Q inside the dynamic range (left side in FIG. 8) from the density level Fd.
Is determined.

In step a8, with respect to the image data in the memory M1, a density level Fb equal to or higher than the lower limit density Fa of the specified range and equal to or higher than the specified frequency Q is searched for. This density level Fb
Is within the dynamic range from the density level Fa (FIG. 8).
Is defined as the first density level having a density level equal to or larger than the predetermined number Q of pixels. Each density level F
The specified frequencies Q of c and Fb may be different from each other. Thus, the density levels Fc and Fb are determined based on the density levels Fa and Fd and the specified frequency Q.

In step a9, the coordinates of the pixels having the density levels Fa to Fd obtained in the respective cases 1 to 3 are extracted based on Table 1 described above.

In step a9, when the density level is F
Coordinates having a density level lower than a and higher than Fd are also extracted based on the image data in the memory M1.

In case 2 or 3 above, FIG.
In step 1, further arithmetic processing is performed based on the stored contents of the memory M2 in which the image data captured with a large exposure amount is stored. FIG. 11 shows the image memory M2
3 is a flowchart for explaining the processing operation of the image data stored in the storage device. In step a10, the memory M2 having the same coordinates as the pixels of the memory M1 having the density levels Fa and Fb obtained in step a9 among the image data stored in the memory M1 captured with the intermediate exposure amount. And the density level in the memory M2 is read out. Table 2 shows the results of this extraction. The coordinates of M2 in Table 2 are the coordinates of the pixels of the memory M2 having the density levels Fa and Fb in the memory M1.

[0042]

[Table 2]

In step a11, each density level Fa,
For each Fb, average values F2a and F2b of the density levels of the pixels extracted from the memory M2 are calculated and calculated based on Expressions 1 and 2.

[0044]

(Equation 1)

Fi is the density level of the pixel in the memory M2 having the same coordinates as the coordinates having the density level Fa of the image data in the memory M1, and the total number of pixels is q. Fj is the density level in the memory M2 having the same coordinates as the pixel having the density level Fb of the image data in the memory M1, and r is the total number of pixels.

In step a12, the density level difference α2 is calculated and obtained. α2 = Fa−F2a (3) In step a13, the exposure coefficient β2 is calculated and obtained. β2 = (Fb−Fa) / (F2b−F2a) (4) The above-described steps a1 to a13 are performed for each of the colors R, G, and B of the image data.

In step a14, the average value β2m of the average values β2R, β2G, and β2B for each of the colors R, G, and B obtained by Equation 4 is calculated. β2m = (β2R + β2G + β2B) / 3 (5) In step a15, the density level of the pixel of the image data in the memory M2 having the same coordinates as the pixel of the image data of the memory M1 having the density level less than the density level Fa Using F2old, and using the calculated density level difference α2 and the exposure coefficient β2m calculated above, Equation 6
Based on the density level F2new of the corrected image data
Is calculated. F2new = Fa + (F2old + α2-Fa) × β2m (6) In the arithmetic unit 17, the above-described steps a5 to a14 are executed, and the density conversion circuit 24 executes the operation of the above-described step a15. In step a16, the color temperature correction circuit 26 performs a color temperature correction calculation of the density level F2new of the corrected image data obtained by the equation (6).

For color temperature correction, the memories provided in the color temperature correction circuit 26 include memories M2 and M3.
Corresponding to each color R, G, B as shown in Table 3.
Gains kR, kG, and kB are set for each.

[0049]

[Table 3]

The image data stored in the memory M2 is image data obtained by imaging the subject with darkness and therefore with a large exposure amount. In this case, since the color temperature is low, the gain kR of the red R is obtained. Is the gain kG of the other colors G and B,
It is set to a value smaller than kB, and for example, as shown in Table 3, kR = 0.8 and kG = kB = 1.0. The density level F2new for each color thus corrected in color temperature
R2, F2newG2, F2newB2 are obtained by Equations 7-9.

F2newR2 = F2newR × kR (7) F2newG2 = F2newG × kG (8) F2newB2 = F2newB × kB (9) In step a17, in the replacement circuit 23, the memory M
The image data within the specified range of the density levels Fa to Fd is directly derived without replacement, and
For the image data less than the above, the image data in the memory M2 is calculated as described above to derive the density level of the corrected image data for each color obtained by the above Expressions 7 to 9. In this way, the dynamic range is extended to the one with the larger exposure amount.

In case 1 or 3 above, FIG.
The operation shown in FIG. 2 is performed. FIG. 12 is a flowchart for explaining the operation in case 1 or 3. Steps a20 to a27 in FIG. 12 correspond to steps a10 to a17 in FIG. 8 described above, and image data stored in the memory M3 of the subject captured with a small exposure amount is used.

In step a20, of the image data stored in the memory M1 taken at the intermediate exposure amount, the density levels Fd,
The coordinates of the coordinates of the memory M3 having the same coordinates as the pixels of the memory M1 having Fc are extracted, and the density level in the memory M3 is read out in the same manner as in Table 2 described above.

In step a21, each density level Fc,
For each Fd, average values F1d and F1c of the density levels of the pixels extracted from the memory M3 are calculated and calculated based on Expressions 1 and 2.

[0055]

(Equation 2)

Fk is the density level of the pixel in the memory M3 having the same coordinates as the coordinates having the density level Fd of the image data in the memory M1, and the total number of pixels is u. Fh is the density level in the memory M3 having the same coordinates as the pixel having the density level Fc of the image data in the memory M1, and v is the total number of pixels. In step a22, a density level difference α1 is calculated and obtained. α1 = Fd−F1d (12) In step a23, the exposure coefficient β1 is calculated and obtained. β1 = (Fd−Fc) / (F1d−F1c) (13) Regarding the above-described steps a20 to a23,
This is performed for each of the colors R, G, and B of the image data. In step a24, each of the colors R, G, B obtained by Expression 13
The average value β1m of each of the average values β1R, β1G, and β1B is calculated and obtained. β1m = (β1R + β1G + β1B) / 3 (14) In step a25, the density level of the pixel of the image data in the memory M3 having the same coordinates as the pixel of the image data in the memory M1 having the density level lower than Fa. Using F1old, and using the calculated density level difference α1 and the exposure coefficient β1m calculated above,
5, the density level F1ne of the corrected image data
Calculate and obtain w. F1new = Fd + (F1old + α1−Fd) × β1m (15) In the arithmetic unit 17, the above-described steps a20 to a24 are executed, and the density conversion circuit 24 executes the above-described operation of step a25. In step a26, the color temperature correction circuit 26 performs a color temperature correction calculation of the density level F1new of the corrected image data obtained by equation (15). The image data stored in the memory M3 is image data obtained by imaging the subject brightly and therefore with a small amount of exposure. In this case, since the color temperature is high, the gain kB of blue B is changed to another The gain is set to a value smaller than the gains kR and kG of the colors R and G,
For example, as shown in Table 3 above, kB = 0.8 and kR = kG
= 1.0 is set. The density levels F1newR1 and F1new for each of the colors R, G, and B thus corrected in color temperature.
G1 and F1newB1 are obtained by Expressions 16 to 18. F1newR1 = F1newR × kR (16) F1newG1 = F1newG × kG (17) F1newB1 = F1newB × kB (18) In step a27, in the replacement circuit 23, the memory M
The image data within the specified range of the density levels Fa to Fd is directly derived without replacement, and the density level Fd
Is calculated, the image data in the memory M3 is calculated as described above to derive the density level of the corrected image data for each color obtained by Expressions 16 to 18 described above. In this way, the dynamic range is extended to the one with the larger exposure amount.

FIG. 13 shows the dynamic range extending device 9.
FIG. 4 is a diagram for explaining image data obtained by the above. The density level in the specified range of the density levels Fa to Fd in the area P1 of the image data obtained at the intermediate exposure amount and the gradient of the density level correspond to the density adjustment in the large and small exposure areas P2 and P3. A correction operation using the exposure coefficient is performed, and thus the characteristic L4 is added to the characteristic L4.
5, an extended dynamic range in which L6 is linearly continued. In the above-described embodiment, the dynamic range DR is such that the density level is determined to be 0 to 255, and for example, Fa = 10, Fb = 20, Fc = 230, Fd =
240.

In the dynamic range compression device 10 to which the corrected image data from the dynamic range expansion device 9 is given, for example, when the dynamic range in a cathode ray tube or a liquid crystal display device is narrow as indicated by reference numeral 31 in FIG. In order to maintain a relative brightness relationship, and to obtain an easy-to-view image that has been converted to an appropriate level even if a wide dynamic range image is biased toward dark or bright sides as a whole. Can be. In another embodiment of the present invention, the range 31 of this dynamic range is, for example, 0 to
A density level range of 255 may be used.

[0059]

According to the first to third and fifth aspects of the present invention, since the dynamic range can be extended, the present invention can be implemented in a digital still camera, a video camera, or the like, for example. It is possible to take a picture when a subject requiring a wide dynamic range such as an outdoor scene is required, and it is possible to take a picture without distinction between normal light and backlight. Moreover, according to the present invention, since a pseudo contour hardly occurs while having a wide dynamic range, the present invention can be advantageously applied to image processing such as contour line extraction. Further, when the image data is color image data, there is almost no color shift, so that color analysis can be performed. Furthermore, according to the present invention, the occurrence of false contours and unnatural density level changes caused by photographing conditions, camera characteristics for photographing, analog / digital conversion characteristics, etc.
It is possible to cope with various combinations of optical systems, cameras, and analog / digital converters of video signals which are prevented by the image synthesis method of the present invention and are not designed specifically or whose characteristics are not confirmed. An excellent effect that the invention can be implemented for general purpose is achieved. Further, according to the present invention, even when the difference between the bright part and the dark part of the image data is large, the change in the density level in each part can be expressed, and therefore, the appearance with the gradation change of the density can be obtained. Can be output as a natural image.

According to the present invention, the density levels F2old and F1old of the second image data are expressed as follows.
Density level difference α2, α1 and exposure coefficient β2m, β1
m, the density level F2ne of the corrected image data
w and F1new can be obtained by calculation.

According to the present invention, when the image data is color image data, the exposure coefficient β2
m and β1m are exposure coefficient β2R, β2G, β for each color.
2B; average value of β1R, β1G, and β1B, which is excellent in color reproducibility and color R, G even when there is a variation in sensor sensitivity difference and amplification factor for each color R, G, B. , B, the influence of the black level difference can be reduced so that a false contour does not occur. in this case,
The density level difference is used independently and individually for each of the colors R, G, and B.

According to the eighth and thirteenth aspects of the present invention, the corrected image data F2new and F1new are corrected in color temperature according to the magnitude of the exposure of the second image data. Can be prevented from appearing reddish in image data having a large color temperature and thus low in color temperature, and can be prevented from appearing bluish in image data having a small exposure amount and therefore having a high color temperature.

According to the ninth and tenth aspects of the present invention, the average value F2a, of the second image data used for calculating the density level differences α2, α1 and the exposure coefficient β2m, β1m.
By using F2b; F1d and F1c, a high-accuracy value with a small error can be calculated and obtained. Therefore, the density levels F2new and F1 of the corrected image data can be obtained.
new can be obtained with high accuracy.

According to the eleventh aspect of the present invention, as described above, the exposure coefficient β2m, β1
m is an exposure coefficient β2R, β2G, β2B for each color; β
Since the average value of 1R, β1G, and β1B is used, the error can be reduced as described above, and a highly accurate operation can be performed.

According to the twelfth aspect of the present invention, one of the density levels Fa and Fd for setting the specified range of the first image data.
Since the other density levels Fb and Fc which are inside the dynamic range are equal to or larger than the predetermined number of pixels, the calculation of the exposure coefficient β2m and β1m can be performed with high accuracy.

According to the fourteenth aspect of the present invention, for example, the second and third image data having a large exposure and a small exposure are used above and below the dynamic range of a first image obtained at an intermediate exposure. By using the exposure amount ratio while correcting and adjusting the density levels, density conversion can be performed and the dynamic range can be expanded sufficiently.

According to the present invention, it is possible to extend not only image data but also a dynamic range of a detector for measuring a physical quantity to be measured such as voltage and current of an electric signal, temperature and humidity. become able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a dynamic range extending device 9.

FIG. 3 is a diagram showing the relationship between the brightness of a subject and the density level of output image data when the exposure amount of image data by the camera 7 is changed.

FIG. 4 is a diagram for describing a subject used for describing one embodiment of the present invention.

FIG. 5 is a diagram for explaining image data of the subject in FIG.

FIG. 6 is a view for explaining image data of a subject having a large exposure amount when the subject in FIG.

FIG. 7 is a diagram for explaining image data of a small exposure amount when the subject in FIG. 4A is imaged by the camera 7;

FIG. 8 is a histogram obtained according to the present invention.

FIG. 9 shows a dynamic range extending device 9 shown in FIG.
3 is a simplified block diagram showing the overall operation of FIG.

FIG. 10 is a flowchart specifically showing an operation 28 in FIG. 9;

FIG. 11 is a flowchart specifically showing an operation 29 of FIG. 9;

FIG. 12 is a flowchart specifically showing an operation 30 of FIG. 9;

FIG. 13 is a diagram for explaining image data obtained by the dynamic range extending device 9.

FIG. 14 is a diagram showing a result of dynamic range expansion according to the first prior art.

FIG. 15 is a diagram showing a result of extending a dynamic range according to the second prior art.

FIG. 16 is a diagram showing a result of extending a dynamic range according to a third prior art.

[Explanation of symbols]

 7 Camera 8 Analog / Digital Converter 9 Dynamic Range Extender 10 Dynamic Range Compressor 11 Image Sensor 12 Condenser Lens 15 Image Switching Circuit 17, 18 Arithmetic Circuit 23 Substitution Circuit 24, 25 Density Conversion Circuit 26, 27 Color Temperature Correction Circuit M1, M2, M3 memory

Claims (17)

[Claims] 1. A method of extending a dynamic range of an image in which a single image data with an extended dynamic range is obtained from image data of a plurality of screens obtained by imaging the same subject with different exposure amounts. Of the image data having different exposure amounts, the density levels at both ends or one end of the dynamic range of the reference image data in the same subject portion are adjusted to the density levels α1 and α2 of the image data having different exposure amounts. At the same time, the change amount (F2b-F2b-) of the image data having different exposure amounts with respect to the change amount (Fb-Fa, Fd-Fc) of the reference image data in the same subject portion.
F2a, an exposure coefficient β2 which is a ratio of F1d-F1c)
A method for extending a dynamic range of an image, comprising correcting image data having different exposure amounts from reference image data using m and β1m. 2. The image data based on the obtained image data having an extended dynamic range of a single sheet,
2. The method for extending a dynamic range of an image according to claim 1, wherein the dynamic range can be extended to a desired dynamic range by repeating the above processing. 3. Obtaining first image data picked up with a certain exposure amount and second image data picked up with an exposure amount larger than the first image data, wherein one of the dynamic ranges of the first image data is obtained. A density level difference α2 between the density level Fa represented by the image data at the end and the density level F2a represented by the image data at the other end of the dynamic range of the second image data is determined. Calculating a change amount (Fb-Fa) of a density level with respect to a subject portion represented by the one end image data; and changing a density level with respect to the subject portion represented by the other end image data of the dynamic range in the second image data Exposure coefficient β2m, which is a ratio to the amount (F2b−F2a), is obtained. Based on the density level difference α2 and the exposure coefficient β2m, the second image data A method of correcting the density level F2old of the first image data to obtain corrected image data F2new continuous to the one end of the dynamic range of the first image data. 4. A density level F of the corrected image data.
2new is: F2new = Fa + (F2old + α2-Fa) × β
4. The method of claim 3, wherein the dynamic range is 2m. 5. Obtaining first image data imaged at a certain exposure amount and second image data imaged at an exposure amount smaller than the first image data, wherein one of the dynamic ranges of the first image data is obtained. The density level difference α1 between the density level Fd represented by the image data at the end and the density level F1d represented by the image data at the other end of the dynamic range of the second image data is determined. Calculating a change amount (Fc-Fd) of a density level with respect to a subject portion represented by the one end image data; and changing a density level with respect to the subject portion represented by the other end image data of the dynamic range in the second image data. Exposure coefficient β1m, which is a ratio to the amount (F1d−F1c), is obtained. Based on the density level difference α1 and the exposure coefficient β1m, the second image data A method of extending the dynamic range of an image, comprising: correcting the density level F1old of the first image data to obtain corrected image data F1new continuous to the one end of the dynamic range of the first image data. 6. A density level F of the corrected image data.
1new is: F1new = Fd + (F1old + α1-Fd) × β
The method of extending a dynamic range of an image according to claim 5, wherein the dynamic range is 1m. 7. The image data is color image data for each of red R, green G, and blue B, and the exposure coefficients β2m and β1m are exposure coefficient β2R, β2R obtained from the image data for each color. β2G, β2B; β1
7. The method according to claim 1, wherein the average value of R, .beta.1G and .beta.1B is averaged. 8. The corrected image data F2n for each color
ew, F1new, and the corrected image data F2ne
When the image data F2old used for obtaining w is the image data with the larger exposure amount, the gain of red is reduced compared to the gain of blue to correct the color temperature, and the corrected image data F1new is 8. The image processing apparatus according to claim 1, wherein when the image data F1old used for obtaining the image data has a smaller exposure amount, the blue temperature is reduced compared to the red gain to correct the color temperature. A method of extending a dynamic range of an image according to one of the above. 9. A first memory for storing first image data having a plurality of density levels imaged at a certain exposure amount, and a first image data having an exposure amount larger than the exposure amount of the first image data. A second memory for storing second image data having a plurality of density levels obtained by imaging the same subject; and the large exposure amount within a dynamic range of the density level of the first image data stored in the first memory. A plurality of predetermined density levels F on the side corresponding to the
a, Fb, the density level Fa outside the dynamic range, the density level further outside, and the predetermined outside density level Fa
First extracting means for extracting the coordinates of the pixel of the first memory having the density level of the density level Fb which is further inside than the first memory; and extracting the pixels of the second memory having the same coordinates as the coordinates extracted by the first extracting means. The second extracting means to be extracted, and the average values F2a and F2b of the density levels of the pixels extracted from the second memory are obtained for each of the predetermined density levels Fa and Fb in response to the output of the second extracting means. An average value calculating means for responding to the output of the average value calculating means to adjust the density level of the second image data to a density level outside the dynamic range for adjusting the density level to the density level of the first image data; The density level difference α2, α2 = Fa−F2a with respect to Fa is obtained, and the ratio of the density level gradient of the first image data to the gradient of the density level of the second image data. A first calculating means for obtaining light quantity coefficients β2m, β2m = (Fb-Fa) / (F2b-F2a); and a response to the output of the second extracting means, which is more dynamic than the predetermined density levels Fa and Fb of the first memory. The density level of the pixel in the second memory having the same coordinates as the coordinates of each pixel having the density level further outside the range is represented by F2o.
ld, the density level F2 of the corrected image data
new, F2new = Fa + (F2old + α2-Fa) × β
And a second calculating means for calculating 2m 2. 10. A first memory for storing first image data having a plurality of density levels imaged at a certain exposure amount, and a first image data having an exposure amount smaller than the exposure amount of the first image data. A second memory for storing second image data having a plurality of density levels obtained by imaging the same subject, and the small exposure amount within a dynamic range of the density level of the first image data stored in the first memory. A plurality of predetermined density levels F on the side corresponding to the
Among d and Fc, the density level Fd located outside the dynamic range, the density level located further outside, and the predetermined outside density level Fd
First extracting means for extracting the coordinates of the pixel of the first memory having the density level of the density level Fc which is further inward than the first memory; Second extraction means to be extracted and average values F1d and F1c of the density levels of the pixels extracted from the second memory are obtained for each of the predetermined density levels Fd and Fc in response to the output of the second extraction means. An average value calculating means, and a density level which is closer to the outside of a dynamic range for adjusting the density level of the second image data to the density level of the first image data in response to the output of the average value calculating means. The density level difference α1, α1 = Fd−F1d with respect to Fd is obtained, and the ratio of the density level gradient of the first image data to the density level gradient of the second image data. A first calculating means for calculating light quantity coefficients β1m, β1m = (Fd−Fc) / (F1d−F1c); The density level of the pixel of the second memory having the same coordinates as the coordinates of each pixel having the density level further outside the range is F1o.
ld, the density level F1 of the corrected image data
new, F1new = Fd + (F1old + α1-Fd) × β
And a second calculating means for calculating 1m 2. 11. The first and second image data are red R,
Color image data for each color of green G and blue B, and the first calculating means calculates the exposure coefficient β2R, β2G, β2 for each color based on the first and second image data for each color.
B; β1R, β1G, β1B are obtained, and the exposure coefficient β2R, β2G, β2B for each color is obtained; β1R, β1G, β1
11. The apparatus for expanding the dynamic range of an image according to claim 9, wherein the average value β2m, β1m of B is obtained and provided to the second calculating means. 12. The first extracting means includes: (a) means for creating a histogram representing the number of pixels for each density level of the first image data stored in the first memory; and (b) output of the histogram creating means. Among the predetermined density levels Fa and Fb; Fd and Fc, one of the predetermined density levels Fa and Fd is set closer to the outside of the dynamic range than the other predetermined density levels Fb and Fc; Means for determining the other predetermined density level Fb, Fc as the first density level having a density number equal to or more than a predetermined number of pixels within the dynamic range from the one predetermined density level Fa, Fd. Device for extending the dynamic range of an image according to one of claims 9 to 11, characterized in that: 13. (a) The first and second image data are:
And (b) when the exposure amount of the second image data is larger than the exposure amount of the first image data, the red gain is changed to the blue gain. A color temperature correction memory for setting the blue gain to be lower than the red gain when the exposure amount of the second image data is small; and (c) a color temperature correction memory. The gain stored in
The apparatus according to any one of claims 9 to 12, further comprising a color temperature correction calculating unit that multiplies the corrected image data (F2new, F1new). 14. A first memory for storing first image data having a plurality of density levels imaged at a certain exposure amount, and a first image data having an exposure amount larger than the exposure amount of the first image data. A second memory for storing second image data having a plurality of density levels of the same subject, and a plurality of images of the same subject as the first image data with an exposure smaller than the exposure of the first image data; A third memory storing third image data having a density level, and a density level of the first image data having a large exposure amount within a dynamic range of the density level of the first image data stored in the first memory. Outside the specified range between a predetermined first density level Fa on one side corresponding to the first side and a second density level Fd on the other side corresponding to the smaller exposure amount, and Density Range determination means for determining whether the first image data is located outside of the first density level Fd or the second density level Fd. When it is located outside the density level Fa, a third density level Fb located inside the dynamic range of the first density level Fa is determined on the one side of the dynamic range, and the third density level is equal to or lower than the first density level Fa. F
first extracting means for extracting the coordinates of the pixels of the first image data stored in the first memory having the density level of b, and pixels of the second memory having the same coordinates as the coordinates extracted by the first extracting means And an average value F2a, F2b of the density levels of the pixels extracted from the second memory for each of the first and third density levels Fa, Fb in response to the output of the second extraction means. A first average value calculating means for determining the density level of the second image data and a density level outside the dynamic range for adjusting the density level of the second image data to the density level of the first image data in response to the output of the first average value calculating means. A density level difference α2, α2 = Fa−F2a with respect to the first density level Fa closer thereto is obtained, and the density level of the first image data with respect to the gradient of the density level of the second image data is calculated. First calculating means for calculating the exposure coefficient β2m, β2m = (Fb-Fa) / (F2b-F2a), which is a ratio of the first exposure level, and the first density level Fa of the first memory in response to the output of the second extracting means. When the density level of the pixel of the second memory having the same coordinate as the coordinate of each pixel having less than F2old is F2old, the density level of the corrected image data F2new, F2new = Fa + (F2old + α2-Fa) × β
2m in response to the output of the range judging means, and when the density level of the first image data is outside the second density level Fd, the second density on the other side of the dynamic range. A fourth density level Fc that is inside the dynamic range from the level Fd is determined, and is equal to or higher than the second density level Fd and the fourth density level Fc.
Extracting means for extracting the coordinates of the pixels stored in the first memory having the density level of, and extracting the pixels of the third memory having the same coordinates as the coordinates extracted by the third extracting means Means for responding to the output of the fourth extracting means, and for each of the second and fourth density levels Fd and Fc, a second average value for obtaining average values F1d and F1c of the density levels of the pixels extracted from the third memory. Calculating means for responding to the output of the second average value calculating means, the second density being outside the dynamic range for adjusting the density level of the third image data to the density level of the first image data. A density level difference α1, α1 = Fd−F1d with respect to the level Fd is obtained, and further, an exposure amount which is a ratio of a gradient of the density level of the first image data to a gradient of the density level of the third image data. A third calculating means for obtaining the numbers β1m, β1m = (Fd−Fc) / (F1d−F1c); The density level of the pixel in the third memory having the same coordinate as the pixel is represented by F1o
ld, the density level F1 of the corrected image data
new, F1new = Fd + (F1old + α1-Fd) × β
And a fourth calculating means for calculating 1m 2. 15. Detection data obtained by measuring the same physical quantity to be measured with mutually different characteristics to obtain a plurality of detection data, and detecting the detection levels at both ends or one end of the dynamic range of the reference detection data with different characteristics. And the detection levels are adjusted to α1 and α2, and the variation (Fb−Fa, Fd−Fc) of the physical quantity to be measured between the reference detection data for the same measurement target and the detection data measured with different characteristics. Detection using the coefficients β2m and β1m, which are the ratios of detection level change amounts (F2b−F2a, F1d−F1c), to correct detection data measured with different characteristics from reference detection data. To extend the dynamic range of the vessel. 16. A first memory for storing first detection data obtained by detecting a physical quantity to be measured with a predetermined characteristic, and a detection level of the first detection data based on the first characteristic, wherein the physical quantity to be measured within a low value range is determined. A second memory for storing second detection data detected by a second characteristic obtained at a higher detection level, and an adjacent detection level within a dynamic range of the detection level of the first detection data stored in the first memory. Of the plurality of predetermined detection levels Fa and Fb on the side where the detection level F is located outside the dynamic range.
a and a first extraction for extracting a time on a time axis of a first memory having a detection level further outward and a detection level Fb which is more inward than the predetermined outward detection level Fa. Means for extracting detection data of the second memory at the same time as the time extracted by the first extraction means; and responding to the output of the second extraction means, detecting the detection level of the second detection data, A detection level difference α2, α2 = Fa−F2a relating to a detection level Fa located outside of the dynamic range for adjusting the detection level to the detection level of the first detection data is obtained. First calculating means for obtaining coefficients β2m, β2m = (Fb−Fa) / (F2b−F2a), which are ratios of the slope of the detection level of the first detection data to the slope. Responsive to the output of the second extracting means, the detection level of the second memory having the detection level further outward than the predetermined detection levels Fa and Fb of the first memory at the same time is F2old. , Detection level F2new of the corrected detection data, F2new = Fa + (F2old + α2-Fa) × β2
and a second calculating means for calculating m. 2. An apparatus for extending a dynamic range of a detector. 17. A first memory for storing first detection data obtained by detecting a physical quantity to be measured with a predetermined characteristic, and detecting a physical quantity to be measured within a high value range with a detection level of the first detection data based on the first characteristic. A second memory for storing second detection data detected by a second characteristic obtained at a higher detection level, and a detection level adjacent to the detection level within a dynamic range of the detection level of the first detection data stored in the first memory. Of the plurality of predetermined detection levels Fd and Fc on the side of the dynamic range,
d and a first extraction for extracting a time on the time axis of the first memory having a detection level further outward and a detection level Fc further inward than the predetermined outward detection level Fd. Means for extracting detection data in the second memory at the same time as the time extracted by the first extraction means; and responding to the output of the second extraction means, setting the detection level of the second detection data to: The detection level difference α1, α1 = Fd−F1d relating to the detection level Fd located outside the dynamic range for adjusting the detection level to the detection level of the first detection data is obtained. First calculating means for obtaining coefficients β1m, β1m = (Fd−Fc) / (F1d−F1c), which are ratios of the slope of the detection level of the first detection data to the slope. Responsive to the output of the second extracting means, the detection level of the second memory having the detection level further outward than the predetermined detection levels Fd and Fc of the first memory at the same time is F1old. , Detection level F1new of the corrected detection data, F1new = Fd + (F1old + α1−Fd) × β1
and a second calculating means for calculating m. 2. An apparatus for extending a dynamic range of a detector.