JP2003244719A - Image composite method and apparatus thereof, and digital still camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image composite method and apparatus thereof capable of smoothing joints of color changes and preventing S/N and resolution from being deteriorated in the case of composing a high sensitivity image and a low sensitivity image to produce a composite image with a wide dynamic range. <P>SOLUTION: The image composite method and apparatus thereof uses only a color signal SH of the high sensitivity image for a range of the lightness darker than a first prescribed value SA, uses only a color signal Sck obtained from a difference signal for a range brighter than a second prescribed value SB brighter than the first prescribed value SA, and uses a color signal resulting from summing the color signal SH of the high sensitivity image and the color signal Sck obtained from the difference signal by using a weighting coefficient βto produce the color signal of the composite image. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image synthesizing method and apparatus for synthesizing a high-sensitivity image and a low-sensitivity image to generate an image having a wide dynamic range. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image synthesizing method and a device for generating a synthetic image with less naturalness, and a digital still camera incorporating the image synthesizing device.

[0002]

2. Description of the Related Art When a digital still camera captures an image of an indoor scene, for example, even if an image of a subject existing in the room is well reflected, the blue sky seen through the window will be blown out, resulting in an unnatural image. Become. This is because the dynamic range of the image is narrow, and in order to solve this problem, conventionally, the dynamic range of the image is widened by capturing and combining two images.

For example, a high-speed shutter is released to capture a low-sensitivity image, a low-speed shutter is released to capture a high-sensitivity image, and two images are combined to create a high-sensitivity image. The outside view of the window is overlapped with the well-sensed low-sensitivity image of the indoor scene. However, in order to combine the two images so that the color changes thereof naturally and smoothly continue, some ingenuity is required.

6A to 6C are graphs for explaining a conventional image synthesizing method, in which the horizontal axis represents the intensity of the input optical signal and the vertical axis represents the color signal S (each color R, G, B). Since the same graph is obtained with, the voltage value of S is shown.
The color signal of each pixel of the low sensitivity image is input to the color signal synthesizing circuit as a color signal gamma converted by the gamma characteristic line L, and the color signal of each pixel of the high sensitivity image is gamma converted by the gamma characteristic line H. The signal is input to the color signal synthesis circuit.

When combining a high-sensitivity image and a low-sensitivity image,
Conventionally, first, as shown in FIG. 6B, a gamma characteristic line gL obtained by multiplying the gamma characteristic line L of a low-sensitivity image by a constant gain g (<1) is created, and then shown in FIG. 6C. Similarly, a predetermined offset value S ₀ (DC component) is added to this gamma characteristic line gL to create a gamma characteristic line S _OS . A signal that follows this gamma characteristic line S _OS is hereinafter referred to as an offset low sensitivity signal.

Then, the point A defined as the design value of the design,
While B (the voltage values of the high-sensitivity signal S _H (signal following the gamma characteristic line H) at points _A and _B are S _A and S _B ), the high-sensitivity signal S _H and the offset low-sensitivity signal S _OS are High sensitivity signal S _H
Weighted addition is performed using the weighting factors α _S and (1−α _S ) according to the above, and the color signal S _C of the combined image is obtained based on the following conventional formula.

S _C (x, y) = α _S S _H (x, y) + (1-α _S ) S _OS (x, y) where S _OS = gS _L (x, y) + S ₀ S ₀ : offset value g: constant gain _{(<1) α S = 1} : for _{S H (x, y) ≦} S a α S = (S H (x, y) -S B) / (S B -S a ): S _A < _SH (x,
y) <S _B α _S = 0: S _H (x, y) ≧ S _B S _L : Low-sensitivity image pixel signal value S _H : High-sensitivity image pixel signal value

That is, conventionally, a composite image is generated using only the high sensitivity signal S _{H in the} range darker than the point A, and in a range brighter than the point B (a range close to the saturation value in the color signal of the high sensitivity image). A pixel signal of a composite image is generated using only the offset low sensitivity signal, and within the range of sections A and B,
As shown by the curve C in FIG. 6C, the color signal of each pixel of the combined image is generated using both the offset low sensitivity signal and the high sensitivity signal.

[0009]

When the high-sensitivity signal and the offset low-sensitivity signal are combined based on the above-described conventional method as in the conventional case, the color of the combined signal at the connection points P and Q in the sections A and B is obtained. There is a problem that the changes are not smoothly connected, and therefore the color characteristics deteriorate near the connection points P and Q, and the synthetic image becomes unnatural. In particular, when the flash is used or when the mechanical shutter and the electronic shutter are used together, the sensitivity ratio between the low-sensitivity image and the high-sensitivity image varies, so that the color change near the connection points P and Q is smooth. There is a problem that it gets worse. Further, since the high-sensitivity signal component becomes small near the connection point Q on the high level side, the S / N becomes poor and the resolution also deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image synthesizing method, an apparatus thereof, and a digital still camera in which a high-sensitivity image and a low-sensitivity image are smoothly connected to each other to suppress unnaturalness of color change of the synthesized image.

[0011]

The above-mentioned object is to combine a high-sensitivity image and a low-sensitivity image to generate a composite image by combining a color signal of the high-sensitivity image and a color signal of the low-sensitivity image. This is achieved by generating the color signal of the composite image from the difference signal of In this way, since the composite image is generated using the difference signal that includes both the image information of the high-sensitivity image and the image information of the low-sensitivity image, the connection between the two images is smooth, and the color characteristics of the composite image are good. Become.

Preferably, the color signal of the composite image is generated based on a signal obtained by subtracting a signal obtained by multiplying the difference signal by a predetermined coefficient from the color signal of the high sensitivity image.
As a result, the amount of information of the high-sensitivity image signal with excellent sensitivity increases, and the S / N and resolution of the composite image are less deteriorated.

More preferably, in the range where the brightness is lower than the first predetermined value, only the color signal of the high sensitivity image is used,
Only the color signal obtained from the difference signal is used in a range brighter than the second predetermined value which is brighter than the predetermined value, and between the first predetermined value and the second predetermined value the color signal of the high sensitivity image and the difference are used. The color signal of the composite image is generated using a color signal obtained by adding a color signal obtained from the signal using a weighting coefficient. With this configuration, the optimum combined signal can be selected for each area, and the unnaturalness of the entire combined image is eliminated.

The above-mentioned object is also to provide a high-sensitivity image and a low-sensitivity image.
Image synthesis method that synthesizes images with each other to generate a synthetic image
And the pixel coordinates are (x, y), the gun of the high sensitivity image
R, G, B signals R after MA conversion_H(x, y), G_H(x, y), B_H(x,
y) and R, G, B signals R after gamma conversion of the low-sensitivity image
_L(x, y), G_L(x, y), B_L(x, y) and R of the high sensitivity image,
G and B signals and R, G and B signals of the low sensitivity image
Coefficient m depending on each _R, M_G, M_BAnd from the composite image
Image synthesis R, G, B signals R_C(x, y), G_C(x, y), B_C(x, y)
To R_C(x, y) ＝ R_H(x, y) -m_R(R_H(x, y) -R_L(x, y)) G_C(x, y) ＝ G_H(x, y) -m_G(G_H(x, y) -G_L(x, y)) B_C(x, y) ＝ B_H(x, y) -m_B(B_H(x, y) -B_L(x, y)) It is achieved by asking for.

According to this structure, since the composite image is generated using the difference signal including both the image information of the high sensitivity image and the image information of the low sensitivity image, the connection between the two images becomes smooth and the composite image The color characteristics are good, and the S / N and resolution of the composite image are good.

Preferably, when the signals before the combination are a luminance signal and a color difference signal, the luminance signal and the color difference signal are converted back into R, G, B signals and the combination is performed. And This makes it possible to deal with the case where the luminance signal and the color difference signal are output from the solid-state imaging device.

The above-mentioned object is to perform the image synthesis for synthesizing a high-sensitivity image and a low-sensitivity image to generate a synthesized image from the difference signal between the luminance signal of the high-sensitivity image and the luminance signal of the low-sensitivity image. This is achieved by generating a luminance signal for the image.

The above object is also to provide a luminance signal Y _H (x, y) and a color difference signal Cr _{H of} a high-sensitivity image, where the pixel coordinates are (x, y).
(x, y), Cb _L (x, y) and the luminance signal Y _L (x, y) of the low-sensitivity image and the color difference signals Cr _L (x, y), Cb _L (x, y) are combined. Luminance signal Y _C (x, y) and color difference signals Cr _C (x, y) and Cb _C (x, y) of the combined image
In generating a said _{m Y Y H (x, y} ) and the Y _L (x,
coefficient dependent on y), and a coefficient which depends the m _C the coefficient _{m Y, Y C (x,} y) = Y H (x, y) -m Y (Y H (x, y) -Y L (x , y)) Cr _C (x, y) = (1-m _Y ) Cr _H (x, y) + m _C Cr _L (x, y) × Y
_C (x, y) / Y _L (x, y) Cb _C (x, y) = (1-m _Y ) Cb _H (x, y) + m _C Cb _L (x, y) × Y
_This is achieved by providing an arithmetic means for obtaining _C (x, y) / Y _L (x, y). With these configurations, it is possible to generate a composite image in which the color change is smooth from the luminance signal and the color difference signal, the color characteristics are excellent, and the S / N and the resolution are good.

A digital still camera that achieves the above object is a solid-state image pickup device for picking up a high-sensitivity image of a subject and a low-sensitivity image of the subject, and the high-sensitivity image and the low-sensitivity image captured by the solid-state image pickup device. The image synthesizing apparatus for synthesizing the image as described above, and the recording means for recording the synthesized image synthesized by the image synthesizing apparatus on the recording medium. With this configuration, it is possible to capture an image with little unnaturalness and a wide dynamic range.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an image synthesizing circuit mounted on a digital still camera according to the first embodiment of the present invention. This image synthesizing circuit includes a gain adjusting circuit 1a for white-balancing a color signal (RGB signal) in a high sensitivity mode output from a solid-state image sensor such as CCD or CMOS, and a low sensitivity output from the solid-state image sensor. A gain adjusting circuit 1b for white-balancing a mode color signal (RGB signal), a gamma converting circuit 2a for gamma converting a gain adjusted high sensitivity mode color signal, and a gain adjusting low sensitivity mode color signal. A gamma conversion circuit 2b that performs gamma conversion, a color signal synthesis circuit 3 that captures the outputs of both gamma conversion circuits 2a and 2b and synthesizes color signals of each pixel, and an output signal of the color signal synthesis circuit 3 that captures, for example, a color image signal. And a color signal processing circuit 4 for performing processing such as separating the luminance signal and the color difference signal.

FIG. 2 is a diagram for explaining an image synthesizing method according to the first embodiment of the present invention. In this embodiment, first, the high sensitivity signal S _H of the gamma characteristic line H shown in FIG.
And taking a difference signal (range hatched in the figure) of the low sensitivity signal S _L of the gamma characteristic line L, and the difference signal multiplied by k (<
1) the signal is subtracted from the high-sensitivity signal line H signal (hereinafter. Referred approximated synthesized signal) S _CK and _{S CK (x, y) =} S H (x, y) -k (S H (x, y ) −S _L (x, y)). (x, y) is the coordinate position of each pixel of the solid-state image sensor. Then, using this approximate combined signal S _CK , the color signal S _C of the combined image is calculated by the following equation.

S _C (x, y) = (1−β _S ) _SH (x, y) + β _S S _CK (x, y) where the value of β _S is S _H (x, y) ≦ for _{S a: β S = 0 S} a <S H (x, y) < for _{S B: β S = (S} H (x, y) -S a)
_{/ (S B -S A) S} H (x, y) For ≧ S _B: a beta _S = 1.

FIG. 2B is a graph for explaining the color signal output synthesized by the above equation. In this embodiment,
Image synthesis is performed using the high-sensitivity signal S _H and the approximate synthesis signal S _{CK. In a} region darker than the point A in sections A and B, the high-sensitivity signal S _H alone is used to generate the color signal of the synthesized image. In an area brighter than point B (area in which the high-sensitivity signal is close to saturation), the color signal of the composite image is generated using only the approximate composite signal.
Then, in the sections A and B, the color signal of the combined image is generated using the high sensitivity signal and the approximate combined signal as indicated by the characteristic line D determined by the above equation.

As described above, according to the image synthesizing method of the present embodiment, the gradients of the high-sensitivity signal S _H and the approximate synthetic signal S _CK are close to each other (to select k to be appropriately small), so that the coefficient β _The combined signal due to the weighting of _S is smoothly connected. Therefore, a composite image with good color characteristics can be obtained.

Further, even when there is a variation in the sensitivity ratio between high sensitivity and low sensitivity, such as when a flash is used or when a mechanical shutter and an electronic shutter are used together, the approximate composite signal only changes smoothly. Therefore, section A,
The smoothness of the combined signal in the region near the connection portions P and Q of B does not deteriorate, and good color characteristics are maintained.

[0027] Furthermore, section A, connecting portion B, even particularly high level side Q, since it is close to the coefficient "1" (1-β _S k), the high-sensitivity signal component is small Therefore, the S / N is good, the resolution is not deteriorated, and a good composite image can be generated.

The image synthesizing method described above can be configured as software that operates on a personal computer or the like, so that the user can arbitrarily adjust the values of k and β. However, the hardware is incorporated into the image processing circuit of the digital still camera or the solid-state imaging device as hardware, and simultaneously (when two solid-state imaging devices are mounted) or continuously (one solid-state imaging device is mounted). In this case, it is preferable that the two captured images are combined on the spot and stored in the recording medium. Incidentally, the above-mentioned color signal S is actually an R, G, B signal.
Details of the above equation using the B signal are shown in FIG.

Next, a second embodiment of the present invention will be described. In the above-described first embodiment, the R, G, and B signals output from the solid-state imaging device are used as they are to generate the color signal of the composite image. However, depending on the solid-state imaging device,
There is also one that converts the R, G and B signals into a luminance signal Y and color difference signals Cr and Cb and outputs them. The second embodiment deals with such a case, and converts the luminance signal Y and the color difference signals Cr and Cb output from the solid-state imaging device into R, G, and B signals again, and the first embodiment The above-described synthesizing process is performed, and then the luminance signal Y and the color difference signals Cr and Cb are converted again.

The signal of each pixel (x, y) in the first embodiment is one of R, G and B, but R and G obtained by converting the luminance signal Y and the color difference signals Cr and Cb. , B signal is
Since the signal of each pixel (x, y) has three color components of R, G, B, by performing the combining process once,
The synthesis of G and B will be performed in parallel. Also in this second embodiment, the same effect as that of the first embodiment can be obtained.

FIG. 4 is a block diagram of an image synthesizing apparatus according to the third embodiment of the present invention. The image signal synthesis circuit 10 of the image synthesis apparatus according to this embodiment is configured to output the luminance signal Y and the color difference signal C in the high sensitivity mode output from the solid-state imaging device.
r, Cb, luminance signal Y and color difference signal C in low sensitivity mode
r and Cb are input, and the image signal synthesizing circuit 10 performs image synthesizing by processing as follows without converting these luminance signal Y and color difference signals Cr and Cb into R, G and B signals. To do.

The synthesized luminance signal Y _C is expressed by the following equation (coordinates of each pixel) similar to the R, G, B signals according to the first embodiment.
The notation of (x, y) is omitted. ) Y _C = Y _H −β _Y k (Y _H −Y _L ), where Y _H : high sensitivity mode luminance signal Y _L : low sensitivity mode luminance signal k: gain (<1) β _Y : by coefficient calculate.

Further, the value of the coefficient beta _{Y is, β Y = 0 (Y H} ≦ Y A) β Y = (Y H -Y A) / (Y B -Y A) (Y A <Y H <Y B ) Β _Y = 1 (Y _H ≧ Y _B ), where Y _A is the brightness signal value in the high sensitivity mode at point _A , Y _B is the brightness signal value in the high sensitivity mode at point B.

As described above, the equation for obtaining the combined signal Y _C of the luminance signals is the same as the R, G, B signals (S signals) of the first embodiment. R, like Y
This is because, like the G and B signals, the magnitude of the luminance has a saturation characteristic according to the brightness. However, the color difference signal does not have the saturation characteristic, and the characteristic line C _H (color difference signal of the high sensitivity image) is shown in FIG.
As shown in, the color difference becomes zero (white) as it gets brighter.

Therefore, the synthesizing formula of the color difference signal is as follows: Cr _C = (1-β _Y ) Cr _H + β _Y k _C Cr _L × Y _C / Y _L Cb _C = (1-β _Y ) Cb _H + Β _Y k _C Cb _L × Y _C / Y _L

[0036] Thus, the color difference signals Cr, as weighting factor beta _Y for Cb, be used the values of the weighting factor beta _Y of the luminance signal differs from the first embodiment. This is because the values of Y _H , Y _A , and Y _{B in} the equation that determines the value of the weighting coefficient β _Y are determined by the luminance signal indicating the saturation characteristic.

Further, in this embodiment, the color difference of the low sensitivity image is
Signal (characteristic line C in FIG. 5_L) Value is dominant in the composite signal
Within the range (brighter than point B), that is, the above Cr_C，
Cb_CIn the second term in the synthetic expression of, the gain multiplication of the luminance signal (Y_C
/ Y_L) And the coefficient k _CIt is multiplied by (≦ 1).
By multiplying the gain of the luminance signal, the color of the composite image will be good.
So that it doesn't look too natural
The coefficient k_CI am hanging.

As described above, according to this embodiment, the luminance signal and the color difference signal of the composite image can be generated from the luminance signal and the color difference signal of the high sensitivity image and the luminance signal and the color difference signal of the low sensitivity image. it can.

In each of the above embodiments, the weighting factors β _S ,
The value of β _Y is a simple linear function of the high-sensitivity signals S _H and Y _H , but in order to obtain smoother connectivity, color characteristics, and resolution, the region is further subdivided and the value of the weighting coefficient is set. It is also possible to do so. Further, although the value of the weighting coefficient is determined depending only on the high sensitivity signal, it is also possible to determine the value of the weighting coefficient using the low sensitivity signal.

Although each of the above embodiments has been described with the coefficient k and the coefficient β as independent values, since kβ is integrated as the coefficient of the difference signal in the actual processing, one coefficient m is used. May be treated as Furthermore, the present invention is not limited to still image synthesis, but can also be applied to moving image synthesis.

[0041]

According to the present invention, when a high-sensitivity image and a low-sensitivity image are combined, the color change in the vicinity of the connection portion becomes smooth, and the color characteristics of the combined image are improved. Further, even if there is a variation in the sensitivity ratio between the high-sensitivity image and the low-sensitivity image, the smoothness of the color change of the composite image does not deteriorate in the area near the connection portion, and good color characteristics are maintained. Furthermore, the components of the high-sensitivity image greatly contribute to the vicinity of the connection portion, especially on the high level side, so that the S / N is good and a high-resolution composite image can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image composition apparatus according to a first embodiment of the present invention.

FIG. 2 is a graph illustrating an image synthesizing method according to the first embodiment of the present invention.

FIG. 3 is a detailed diagram of a composition formula used in the image composition method according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of an image composition device according to a third embodiment of the present invention.

FIG. 5 is a graph illustrating an image synthesizing method according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conventional image synthesizing method.

[Explanation of symbols]

1a, 1b Gain adjustment circuit 2a, 2b gamma conversion circuit 3-color signal synthesis circuit 4-color signal processing circuit 10 Image signal synthesis circuit

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/60 H04N 1/40 D 5C079 9/04 1/46 Z F term (reference) 5B057 BA02 BA11 CA01 CA08 CA16 CB01 CB08 CB16 CE08 CE11 CE17 CE18 5C065 AA03 BB48 CC01 DD01 GG21 GG22 GG23 5C066 AA01 BA13 CA07 FA02 KA12 KD02 KD04 KE02 KE03 KE04 KG01 KP02 5C076 AA12 A12 AA19 BA06 5C077 MP08 PP15 PP01 5B01B12B04C04 PP12 PP12 PP32 PP04 PP32 PP04 PP32 PP04 PP32 PP04 PP03 PP32 PP04 PP32 PP04 PP32 PP04 PP12 PP04 PPB

Claims (15)

[Claims] 1. An image synthesizing method for synthesizing a high-sensitivity image and a low-sensitivity image to generate a synthesized image, wherein the synthesized image is obtained from a difference signal between a color signal of the high-sensitivity image and a color signal of the low-sensitivity image. An image synthesizing method characterized by generating a color signal of. 2. The image combination according to claim 1, wherein the color signal of the combined image is generated based on a signal obtained by subtracting a signal obtained by multiplying the difference signal by a predetermined coefficient from a color signal of the high-sensitivity image. Method. 3. The color signal of the high-sensitivity image is used only when the brightness is darker than a first predetermined value, and the color obtained from the difference signal is brighter than a second predetermined value which is brighter than the first predetermined value. Only the signal is used, and between the first predetermined value and the second predetermined value, a color signal obtained by adding a color signal of the high-sensitivity image and a color signal obtained from the difference signal using a weighting coefficient is used. The image synthesizing method according to claim 1 or 2, wherein a color signal of the synthetic image is generated. 4. A high-sensitivity image and a low-sensitivity image are combined and combined.
In the image composition method that generates a composed image, the pixel coordinates
When (x, y), R after gamma conversion of the high-sensitivity image,
G, B signal R_H(x, y), G_H(x, y), B_H(x, y) and the low sensitivity
R, G, B signals R after gamma conversion of the image_L(x, y), G_L(x,
y), B_L(x, y) and husbands of R, G, B signals of the high sensitivity image
Depending on the R, G, and B signals of the low-sensitivity image
Coefficient m_R, M_G, M_BFrom the above, the composite R of the composite image,
G, B signal R_C(x, y), G_C(x, y), B _C(x, y) R_C(x, y) ＝ R_H(x, y) -m_R(R_H(x, y) -R_L(x, y)) G_C(x, y) ＝ G_H(x, y) -m_G(G_H(x, y) -G_L(x, y)) B_C(x, y) ＝ B_H(x, y) -m_B(B_H(x, y) -B_L(x, y)) An image synthesizing method characterized by: 5. When the signal before the combining is a luminance signal and a color difference signal, the luminance signal and the color difference signal are set to R,
The image synthesizing method according to claim 4, wherein the synthesizing is performed by converting the G and B signals again. 6. An image synthesizing method for synthesizing a high-sensitivity image and a low-sensitivity image to generate a synthesized image, wherein the synthesized image is obtained from a difference signal between a luminance signal of the high-sensitivity image and a luminance signal of the low-sensitivity image. A method of synthesizing images, the method including: 7. The luminance signal Y _H (x, y) and the color difference signals Cr _H (x, y), Cb _L (x, y) of the high-sensitivity image when the pixel coordinates are (x, y).
y), the luminance signal Y _L (x, y) and the color difference signal Cr _{L of} the low sensitivity image
(x, y) and Cb _L (x, y) are combined to obtain a luminance signal Y of a combined image.
_{In generating C} (x, y) and color difference signals Cr _C (x, y) and Cb _C (x, y), m _{Y is set} to Y _H (x, y) and Y _L (x, y) Dependent coefficient, m _C is a coefficient dependent on coefficient m _Y , and Y _C (x, y) = Y _H (x, y) −m _Y (Y _H (x, y) −Y _L (x, y) ) Cr _C (x, y) = (1-m _Y ) Cr _H (x, y) + m _C Cr _L (x, y) × Y
_C (x, y) / Y _L (x, y) Cb _C (x, y) = (1-m _Y ) Cb _H (x, y) + m _C Cb _L (x, y) × Y
An image synthesizing method characterized by obtaining as _C (x, y) / Y _L (x, y). 8. An image synthesizing apparatus for synthesizing a high-sensitivity image and a low-sensitivity image to generate a synthesized image, wherein the synthesized image is obtained from a difference signal between a color signal of the high-sensitivity image and a color signal of the low-sensitivity image. An image synthesizing apparatus comprising: a color signal synthesizing unit for generating the color signal of. 9. The color signal synthesizing means generates a color signal of the synthesized image based on a signal obtained by subtracting a signal obtained by multiplying the difference signal by a predetermined coefficient from a color signal of the high sensitivity image. Item 9. The image synthesizing apparatus according to item 8. 10. The brightness of the color signal synthesizing means is first
In the range darker than the predetermined value, only the color signal of the high-sensitivity image is used, and in the range brighter than the second predetermined value, which is brighter than the first predetermined value, only the color signal obtained from the difference signal is used, and the first predetermined value is used. And the second predetermined value, the color signal of the composite image is generated using a color signal obtained by adding the color signal of the high-sensitivity image and the color signal obtained from the difference signal using a weighting coefficient. The image synthesizing device according to claim 8 or 9, characterized in that. 11. A high sensitivity image and a low sensitivity image are synthesized.
In the image composition device that generates a composite image, the pixel coordinates
When (x, y), R after gamma conversion of the high-sensitivity image,
G, B signal R_H(x, y), G_H(x, y), B_H(x, y) and the low sensitivity
R, G, B signals R after gamma conversion of the image_L(x, y), G_L(x,
y), B_L(x, y) and husbands of R, G, B signals of the high sensitivity image
Depending on the R, G, and B signals of the low-sensitivity image
Coefficient m _R, M_G, M_BFrom the above, the composite R of the composite image,
G, B signal R_C(x, y), G_C(x, y), B_C(x, y) R_C(x, y) ＝ R_H(x, y) -m_R(R_H(x, y) -R_L(x, y)) G_C(x, y) ＝ G_H(x, y) -m_G(G_H(x, y) -G_L(x, y)) B_C(x, y) ＝ B_H(x, y) -m_B(B_H(x, y) -B_L(x, y)) The image combination characterized by including a calculating unit
Equipment. 12. The image synthesizing apparatus according to claim 11, further comprising means for converting a luminance signal and a color difference signal into R, G, and B signals before the arithmetic means. 13. An image synthesizing apparatus for synthesizing a high-sensitivity image and a low-sensitivity image to generate a synthesized image, wherein the synthesized image is obtained from a difference signal between a luminance signal of the high-sensitivity image and a luminance signal of the low-sensitivity image. An image synthesizing apparatus, comprising: a synthesizing unit that generates the luminance signal of 1. 14. A luminance signal Y _H (x, y) and a color difference signal Cr _H (x, y), Cb of a high sensitivity image when pixel coordinates are (x, y).
_L (x, y) and the luminance signal Y _L (x, y) of the low-sensitivity image and the color difference signals _{Cr L (x, y),} Cb L (x, y) of the synthesized synthesized image luminance signal Y _{In generating C} (x, y) and color difference signals Cr _C (x, y) and Cb _C (x, y), m _{Y is set} to Y _H (x, y) and Y _L (x, y) Dependent coefficient, m _C is a coefficient dependent on coefficient m _Y , and Y _C (x, y) = Y _H (x, y) −m _Y (Y _H (x, y) −Y _L (x, y) ) Cr _C (x, y) = (1-m _Y ) Cr _H (x, y) + m _C Cr _L (x, y) × Y
_C (x, y) / Y _L (x, y) Cb _C (x, y) = (1-m _Y ) Cb _H (x, y) + m _C Cb _L (x, y) × Y
An image synthesizing apparatus comprising a calculating means for obtaining _C (x, y) / Y _L (x, y). 15. A solid-state image pickup device for picking up a high-sensitivity image of a subject and a low-sensitivity image of the subject, and the high-sensitivity image and the low-sensitivity image captured by the solid-state image pickup device are combined. Item 15. A digital still camera comprising: the image synthesizing apparatus according to any one of items 14 and a recording unit configured to record a synthesized image synthesized by the image synthesizing apparatus on a recording medium.