JP2001224037A - Color image pickup device and image data acquisition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image pickup device that can enhance color reproducibility and expansion of a color image pickup range by accurately reproducing an image pickup characteristic having negative spectral sensitivity. SOLUTION: The color image pickup device having a 3-primary color filter whose R, G and B stimulus value being able to take a negative value follows a prescribed image pickup characteristic at its image pickup element section, is provided with a positive sensitivity filter section where at least one color in the three primary colors of the filter has only a positive sensitivity characteristic of the stimulus value and with a negative sensitivity filter section which has the negative sensitivity characteristic of the stimulus value as a positive sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a single-chip type color image pickup apparatus using one CCD coated with an RGB filter, and a method of acquiring image data in the apparatus.

[0002]

2. Description of the Related Art Single-chip RG using only one CCD
In the B primary color filter color imaging device, the optical filter coated on the imaging section of the CCD has, for example, an arrangement of R (red), G (green), and B (blue) as shown in FIG. FIG. 2 shows an example of the spectral sensitivity of each color filter, and corresponds to the color reproduction range by visual observation. The color information of the subject exposure image projected on the imaging unit is separated into three primary color imaging signals by an optical filter. Then, by using the three primary color imaging signals obtained from the three adjacent pixels, the calculation of F = rR + gG + bB is performed, whereby the color light F at each position can be obtained. Here, r, g, and b indicate the intensity of each of the three primary colors, and are called stimulus values. Each stimulus value is R, G,
It can be determined from the intensity of light detected by the CCD after passing through each color filter of B.

The stimulus values r, g, and b based on the visual color reproduction range have only positive values as shown in FIG. On the other hand, FIG. 3 shows, on a chromaticity diagram, the color reproduction range of the color television standardized by the NTSC system. The color reproduction range according to the NTSC standard is
It is determined based on the output from the CRT, and is indicated by a triangular area having three points R, G, and B as vertices shown in FIG. If the spectral sensitivity (color television ideal imaging characteristics) for performing color reproduction in this range is expressed using the three primary colors R, G, and B of the light, as shown in FIG. Will be taken. In order to realize a camera having such spectral sensitivity, two CCD elements for positive use and negative use are required even in a single-panel type, so that not only is the cost inferior, but also the size of the camera is increased.

Therefore, the conventional single-panel system approximately realizes the ideal image pickup characteristics, and the following two types of the approximation methods can be given. (1) Only the positive sensitivity portion of the ideal imaging characteristic is used and its tail is cut (see FIG. 5). What cut the hem part
If only the portion of the positive sensitivity is used, the saturation of the re-development is reduced due to the lack of the portion of the negative sensitivity, and this is taken into consideration. (2) Use of a linear matrix system. Explaining this with reference to FIG. 4, the negative part on the short wavelength side of the sensitivity characteristic curve of G is substituted by subtracting it from the sensitivity characteristic curve of B, and the negative part on the long wavelength side is substituted by R of the long wavelength side. Substitution is performed by subtracting from the sensitivity characteristic curve.

[0005]

Since the above two methods are approximations to the last, the color imaging range is narrow and the color reproducibility is low. Although it does not cause much problem in consumer use such as recreation, further high performance is required in fields such as medical care and art and art preservation. Even if the color imaging range at the time of shooting is increased, the final color reproduction range cannot exceed the performance of the playback device (display, printer, etc.). But,
Considering the future performance enhancement of the playback apparatus, it is important to increase the color imaging range at the time of shooting, and this is a technical problem to be solved by the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to effectively solve the above-mentioned problems.
A color imaging device having the following features is provided.

[0007] The color image pickup apparatus of the present invention is composed of “R, G, B”.
The image sensor unit has three primary color filters that conform to a "predetermined imaging characteristic in which the stimulus value with respect to can take a negative value". As for the three primary color filters, for at least one of the three primary colors (preferably all three colors), the “positive sensitivity filter section having only the positive sensitivity characteristic portion of the stimulus value” and the “negative sensitivity A negative sensitivity filter section having a characteristic portion as a positive sensitivity ”.

[0008] In the color image pickup apparatus of the present invention having the above configuration, "the intensity of light passing through the positive sensitivity filter unit"
By performing an arithmetic operation (subtraction) based on the "and the intensity of the light passing through the negative sensitivity filter unit", both positive and negative stimulus values can be obtained. That is, one positive imaging element can obtain both positive and negative stimulus values without using two positive imaging elements and negative imaging elements (CCD or the like).

Therefore, the color imaging device of the present invention can accurately reproduce all imaging characteristics (spectral sensitivity) in which the stimulus values for R, G, and B can take negative values. For example,
If this imaging characteristic is the imaging characteristic shown in FIG. 4, the color reproduction error can be extremely reduced within the color reproduction range of the triangular area according to the NTSC standard shown in FIG. Furthermore, according to the present invention, even if the spectral sensitivity corresponds to the color reproduction range further expanded than the color reproduction range shown in FIG. 3, it can be accurately reproduced. Can be. Therefore, it is possible to acquire high-quality image data that can cope with a future improvement in the performance of the reproducing apparatus. Of course, there is no increase in the number of components or the size of the apparatus.

Note that the spectral sensitivity of the entire color image pickup apparatus is determined by integrating three spectral sensitivities of "spectral sensitivity of a photographing optical system", "spectral sensitivity of a color filter", and "spectral sensitivity of a photoelectric conversion unit". Things. The present invention focuses on the "spectral sensitivity of the color filter" among the three spectral sensitivities, and accurately reproduces this spectral sensitivity to bring the overall spectral sensitivity closer to ideal characteristics.

In the color image pickup device of the present invention, it is preferable that the positive sensitivity filter section and the negative sensitivity filter section are provided for pixels adjacent to the image sensor. As a result, the spectral sensitivity can be accurately reproduced by using the above calculation even for a subject existing in a narrow range within the image frame.

The pixel group of the image sensor is divided into two fields every other line (one horizontal line or one vertical line).
When reading out signals from a pixel group belonging to each field, it is preferable that the negative sensitivity filter section is provided only for pixels belonging to one field. When such a configuration is adopted, conventional image data can be obtained from the field in which the negative sensitivity filter section is not included, so that a conventional display device that does not correspond to the color imaging device of the present invention can be used. Even if there is, it can be used effectively.

Further, according to the present invention, there is provided a method for acquiring image data in a color image pickup apparatus provided with an image pickup element section having three primary color filters according to predetermined image pickup characteristics in which stimulus values for R, G, and B can take negative values. You. In this method, for at least one of the three primary colors (preferably all three primary colors) in the filter, a positive sensitivity filter section having only the positive sensitivity characteristic portion of the stimulus value, A negative sensitivity filter section having a sensitivity characteristic portion as a positive sensitivity. Then, new image data is obtained by subtracting "image data obtained from the negative sensitivity filter unit" from "image data obtained from the positive sensitivity filter unit".

In this case, the pixel group of the image sensor is divided into two fields every other line (one horizontal line or one vertical line), and a negative sensitivity filter section is provided only for pixels belonging to one field. It is preferable to perform subtraction on image data obtained from one field and image data obtained from the other field.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The illustrated example describes a case where the spectral sensitivity corresponding to the color reproduction range (triangular area in FIG. 3) according to the NTSC standard is reproduced. FIG.
4A shows only the spectral sensitivity of the R channel in FIG. A broken line indicates a positive sensitivity part, and a solid line indicates a negative sensitivity part. And FIG. 6 (b)
The spectral sensitivity obtained by extracting only the positive sensitivity part in FIG.
FIG. 6C shows the spectral sensitivity obtained by replacing the negative sensitivity part with the positive sensitivity. In the present invention, a color filter having a spectral sensitivity of FIG. 6 (b), and a color filter having a spectral sensitivity of FIG. 6 (c), respectively were prepared, referred to as the color filters R _p, and R _n.

Similarly, FIG. 7A shows only the spectral sensitivity of the G channel in FIG. 4, and FIGS. 7B and 7C show the spectral sensitivity obtained by extracting only the positive sensitivity portion, and FIG. The spectral sensitivities obtained by replacing the negative sensitivities with the positive sensitivities are shown. The color filter G _p having a spectral sensitivity of FIG. 7 (b),
The color filter having the spectral sensitivity of FIG. 7C is called _Gn .

Similarly, FIG. 8 (a) shows only the imaging characteristics of the B channel in FIG. 4, and FIGS. 8 (b) and 8 (c) show the spectral sensitivity obtained by extracting only the positive sensitivity portion, and The spectral sensitivities obtained by replacing the negative sensitivities with the positive sensitivities are shown. The color filter B _p with the spectral sensitivity of FIG. 8 (b),
The color filter having the spectral sensitivity of FIG. 8C is called _Bn .

FIG. 9 shows an example of the arrangement of the respective color filters. This sequence, "R _p and R _n", "G _p and G _n '
Each set of “B _p and B _n ” is arranged adjacent to each other in the vertical direction, and each set is arranged like the G checkered Bayer array shown in FIG. As you can see from the description below,
This arrangement is effective when one frame of image information is divided into two fields every other horizontal line and an image pickup signal is taken out in field units. In addition, it is also possible to adopt R, G, and B stripe methods other than the G checker Bayer arrangement.

In FIG. 9, the odd fields (1, 2,.
3, the line corresponding to the..), R _p, G _p, arrayed B _p, even fields (1 ', 2', 3 ', to the line corresponding to ...) is, R _n , G _n , and B _n are arranged. Of course, contrary to the above, R _n , G _n , and B _n may be arranged in odd fields, and R _p , G _p , and B _p may be arranged in even fields.

FIG. 10 is a block diagram showing a control example using an image pickup device having a color filter having the arrangement of FIG. The imaging device 1 outputs an imaging signal of a specified odd or even field according to a field switching signal from the field selection unit 10. Each of the image signals output from the image sensor 1 is subjected to analog-to-digital conversion in the A / D converter 2 in pixel units, and signals from odd fields are stored in a field memory P, and signals from even fields are stored in a field memory N. Are respectively stored as image data. The image data for each line stored in the field memory P is R _{ps ,} G _ps , B _ps, and the image data for each line stored in the field memory N is R
_{ns' ,} G _{ns' and} B _ns' . The subscript s means a line number.

Next, image data is sequentially read from the field memories P and N, and the subtraction processing section 6
Image data subtraction processing is performed on adjacent positive and negative sensitivity lines. The image data thus obtained is stored in the field memory W. That is, the image data stored in the field memory W is represented by R _s , G _s , B
_Assuming that _s , the relationship between the image signal and the positive sensitivity signal and the negative sensitivity signal is expressed by the following equation. _{R s = R ps -R ns'} G s = G ps -G ns' B s = B ps -B ns'

As described above, when the image data of the positive sensitivity and the image data of the negative sensitivity are stored in units of fields, when the conventional image data is required, the image data consisting of only the positive sensitivity image data (shown in FIG. In the example, it is sufficient to output image data of an odd field), which is convenient for achieving compatibility with a conventional image display device.

Further, as shown in the example of the drawing, if the positive sensitivity color filter and the negative sensitivity color filter are arranged adjacent to each other, the above-described subtraction can be used in the narrow range of the subject so as to be faithful to the ideal imaging characteristics. High quality image data can be obtained. In addition, the sensitivity between the fields of the image sensor 1
If the (photoelectric conversion sensitivities) are different, the sensitivity adjustment using the sensitivity adjuster 3 may be performed on the even-numbered fields in order to accurately reproduce the ideal imaging characteristics.

In the illustrated example, the positive sensitivity signal and the negative sensitivity signal are obtained and subtracted for all three primary colors of the ideal imaging characteristics. However, both signals are obtained and subtracted only for any two colors or only one color. It is good also as doing. For example,
As can be seen from FIG. 4, the influence of the spectral sensitivity characteristic of the negative sensitivity is particularly large in the short wavelength region of about 500 nm.
For only two colors (R) and green (G), a positive sensitivity signal and a negative sensitivity signal may be obtained and subtraction may be performed.

In the above embodiment, the case where the ideal image pickup characteristic shown in FIG. 4 is accurately reproduced is described. However, according to the present invention, the "negative spectral sensitivity" can be accurately reproduced even in a color imaging device using only one imaging device such as a CCD.
It is possible to accurately reproduce even an imaging characteristic (spectral sensitivity) corresponding to a color reproduction range wider than the color reproduction range (triangular area in FIG. 3) according to the TSC standard. That is, according to the present invention, the color imaging range can be expanded more than before,
Therefore, it is possible to acquire high-quality image data that can cope with a future performance improvement of a reproducing apparatus such as a display or a printer.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of an array of color filters.

FIG. 2 is a graph showing the spectral sensitivity of a color filter based on visual perception.

FIG. 3 is a chromaticity diagram illustrating a color reproduction range according to the NTSC standard.

FIG. 4 is a graph showing ideal imaging characteristics corresponding to the color reproduction range of FIG. 3;

FIG. 5 is a graph showing imaging characteristics according to a conventional example in which the ideal imaging characteristics of FIG. 3 are approximated.

FIG. 6 is a graph illustrating the spectral sensitivity of R in the color filter according to the present invention.

FIG. 7 is a graph illustrating the spectral sensitivity of G in the color filter according to the present invention.

FIG. 8 is a graph illustrating the spectral sensitivity of B in the color filter according to the present invention.

FIG. 9 is an explanatory diagram showing an example of an array of color filters according to the present invention.

FIG. 10 is a block diagram illustrating a control example of an imaging apparatus using the color filter of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image sensor 2 A / D conversion part 3 Sensitivity adjustment part 4 Field memory P 5 Field memory N 6 Subtraction processing part 7 Field memory W 10 Field selection part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H04N 1/48 H04N 1/46 A F term (Reference) 4M118 AA10 AB01 BA10 DB03 GC08 GC14 5B047 AB04 BB04 BB06 BC07 5C065 AA01 BB01 CC01 DD02 EE03 EE05 GG02 GG26 GG27 GG30 5C072 AA01 BA19 DA09 QA10 UA18 5C079 HB01 JA13 JA23 MA11 NA03

Claims (8)

[Claims] 1. A color imaging device comprising an image sensor unit having three primary color filters according to predetermined imaging characteristics in which a stimulus value for R, G, and B can take a negative value, wherein the filter is one of three primary colors. For at least one color, a positive sensitivity filter unit having only a positive sensitivity characteristic portion of the stimulus value, and a negative sensitivity filter unit having a negative sensitivity characteristic portion of the stimulus value as a positive sensitivity, Color imaging device. 2. The color imaging apparatus according to claim 1, wherein the filter includes a positive sensitivity filter section and a negative sensitivity filter section for all of R, G, and B. 3. The color imaging apparatus according to claim 1, wherein the predetermined imaging characteristic is a color television ideal imaging characteristic corresponding to a color reproduction range of the NTSC standard. 4. The color image pickup apparatus according to claim 1, wherein said positive sensitivity filter section and said negative sensitivity filter section are provided for pixels adjacent to an image sensor. apparatus. 5. The color image pickup apparatus according to claim 1, wherein the pixel group of the image pickup device section is divided into two fields every other line, and a signal is read from the pixel group belonging to each field. A color imaging device, wherein the negative sensitivity filter unit is provided only for pixels belonging to one field. 6. A color image pickup apparatus provided with an image pickup device section having three primary color filters according to predetermined image pickup characteristics in which a stimulus value for R, G, and B can take a negative value, wherein at least one of the three primary colors in the filters is provided. For the color, a positive sensitivity filter unit having only the positive sensitivity characteristic part of the stimulus value and a negative sensitivity filter unit having the negative sensitivity characteristic part of the stimulus value as the positive sensitivity are provided. Image data obtaining method, wherein new image data is obtained by performing a subtraction between the obtained image data and the image data obtained from the negative sensitivity filter unit. 7. A color image pickup device provided with an image pickup element section having three primary color filters according to predetermined imaging characteristics in which stimulus values for R, G, and B can take a negative value, wherein at least one of the three primary colors in the filters is provided. For the color, a positive sensitivity filter unit having only a positive sensitivity characteristic portion of the stimulus value and a negative sensitivity filter unit having a negative sensitivity characteristic portion of the stimulus value as positive sensitivity are provided, and a pixel group of the imaging device unit is provided. Is divided into two fields every other line, and a negative sensitivity filter section is provided only for the pixels belonging to one field, and the image data obtained from one field and the image data obtained from the other field are provided. An image data acquisition method, wherein new image data is acquired by performing subtraction. 8. The method according to claim 6, wherein the positive sensitivity filter section and the negative sensitivity filter section are provided for all of R, G, and B.