JPS639792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single-chip color imaging device, and more particularly to a color imaging device that takes vertical correlation using a delay circuit for one horizontal scanning period in order to improve resolution.

A single-chip color imaging device that uses a single two-dimensional solid-state imaging device to obtain a color video signal must have a color separation function for at least three colors, and usually a color filter is placed on the imaging device to separate the subject image. A method is adopted in which spatial sampling is performed for each color component.
In this case, it is desirable to effectively use limited pixels to increase sampling efficiency.

However, the video signal has the characteristic that a high resolution is required for the luminance signal, and that even a relatively low resolution of the color signal does not cause any problem in imaging. Considering these characteristics, conventionally, as shown in FIG. 1, green color (which occupies most of the luminance component) is used for odd or even fields formed by extracting only odd or even lines of horizontal scanning lines. G) A widely adopted method is to arrange only signal filters on every other element in both the horizontal and vertical directions, and to alternately arrange red (R) filters and blue (B) filters in between in units of horizontal scanning lines. ing.

However, in an imaging device equipped with the color filter array described above, when each field is left as it is, the G signal forms a checkerboard pattern, and the R and B signals are arranged every other horizontal scanning line, which makes effective use of pixels. It was difficult to say that the image quality was good, and improvements in image quality were desired.

Therefore, a delay circuit is used to create a signal delayed by one horizontal scanning period, and vertical correlation is obtained by adding and subtracting the signal with the real-time signal. A method of supplementing pixels is adopted.

However, when interpolation is performed using the signal delayed by one horizontal scanning period, a strong false color signal may be generated for an incident light image with a large change in brightness in the vertical direction, resulting in a reduction in vertical resolution.

The present invention has been made in view of the above-mentioned problems of conventional color imaging devices, and it is an object of the present invention to provide an imaging device that can suppress the generation of false color signals and obtain high-quality color images.

Next, the present invention will be explained in detail with reference to Examples.

The color imaging device according to the present invention includes a G filter, a G filter,
Three color filters consisting of an R filter and a B filter are arranged in a predetermined positional relationship as shown in FIG. That is, regarding the horizontal scanning line of the solid-state image sensor, the odd field and the even field, which are formed by collecting odd or even lines, have the same filter arrangement, and the G filters in both fields are arranged in a checkerboard pattern. In between, B filters and R filters are arranged alternately for each horizontal scanning line. When white light is incident on an image sensor having the above-mentioned filter arrangement, the electric output signal from the image sensor corresponding to each color is the same amount as that which passes through the color filter and is imaged on the light-receiving surface of the image sensor. It is designed to be.

The color components of the filter are R, as in the above embodiment.
The present invention is not limited to the three primary colors G and B, and a combination of three primary color complementary color filters, a primary color and complementary color filter, or a transparent filter may also be applied.

FIG. 2 is a block diagram showing a color signal separation circuit of an imaging device equipped with the above filter arrangement.

A light image incident through the lens 1 is formed on the light receiving surface of the image sensor 2 having the color filter array shown in FIG. 1, and an electrical output signal corresponding to the amount of incident light is output. The signal output from the image sensor 2 is branched, one directly and the other signal output from the image sensor 2.
One horizontal scanning period (hereinafter referred to as
1H) is input to sample and hold circuits 4, 5, 6, and 7 via a delay line 3 having a delay function. Here, the sample-and-hold circuit 4 extracts only the real-time G signal, and the sample-and-hold circuit 7 extracts only the real-time G signal.
Extract only the G signal delayed by 1H. In addition, the sample and hold circuit 5 receives the real-time R signal and B signal.
Sample and hold circuit 6 alternately extracts every 1H.
extracts the R signal and B signal delayed by 1H alternately every 1H.

An adder circuit 8 is provided which adds the outputs of the sample and hold circuits 4 and 7, and adds the 1H delayed G signal and the real time G signal to perform vertical interpolation and improve horizontal resolution.

Further, a subtraction circuit 12 is provided which subtracts the 1H delayed G signal outputted from the sample and hold circuit 7 from the real time G signal of the sample and hold circuit 4, and the output of the subtraction circuit 12 has a pseudo color as described later. Correction signal ±S to suppress signal generation
becomes. That is, the correction signal ±S becomes +S when the real-time G signal exists and the 1H delayed G signal does not exist, and -S when the real-time G signal and the 1H delayed signal exist together or both exist in the opposite state. If not, it will be zero. The correction signal ±S output from the subtraction circuit 12 is applied to one input terminal of each of adders 13, 14, and 18, which will be described later, and which are provided to derive the G signal, R signal, and B signal, respectively. .

The other sample hold circuits 5 and 6 each have
A switch circuit 9 or a switch circuit 10 whose conduction state changes every 1H is connected to the R signal output terminal 15 in synchronization with the R signal and B signal which change every 1H.
Then, the signal path is switched to output the R signal or the B signal to the B signal output terminal 16. In each of the switch circuit 9 and the switch circuit 10, an adder circuit 13 is provided in front of the output terminal 15 and the output terminal 16.
Alternatively, the adder circuit 14 is inserted. Addition circuit 1
The output of the sample hold circuit 5 via the switch circuit 9 is applied to one input terminal of 3, and the correction signal ±S outputted from the subtraction circuit 12 is applied to the other input terminal, so that both signals are The addition result is output. Similarly, one input terminal of the adder circuit 14 is connected to the output of the sample hold circuit 6 and the subtracter circuit 12.
A correction signal ±S is given, and the added value is output to the output terminal 16. Furthermore, the above subtraction circuit 12
A switch circuit 11 is provided at the output terminal of the sample and hold circuits 5 and 6 and a color signal output terminal 15,
16 is connected to the above switch circuits 9 and 10.
The correction signal ±
S is alternately input to the adder circuit 13 or adder circuit 14 every 1H.

An adder circuit 18 is provided upstream of the G signal output terminal 17 in order to correct the G signal as well, and the correction signal ±S is added to the output of the adder circuit 8 to form the G signal.

Next, the operation of the imaging apparatus having the above configuration will be explained using FIG. 3. Odd-numbered fields and even-numbered fields use the same color filter arrangement, so only the odd-numbered fields will be described.

In the odd field output, from the nth horizontal line to the (n+14)th horizontal line, G, R,
As shown in FIG. 3a, the combination of the B color filters includes a checkered G filter, and R filters and B filters are alternately arranged in units of horizontal lines between the checkered G filters.

Now, for example, the third
Assume that a non-colored optical image with incident light changing between "present" and "absent" as shown in FIG. b is incident. It is assumed that the level "0" in FIG. 1B indicates that there is no incident light, and the level "1" indicates that there is incident light.

G, R, When the B output signals are formed, the G' output signal is output as the signal shown in FIG. 3c, the R' output signal as the signal shown in FIG. 3d, and the B' output signal as the signal shown in FIG. 3e. An output signal obtained by combining the color output signals shown in FIGS. 3c, d, and e is shown in FIG. 3f. That is, the obtained composite output signal differs from the incident light image shown in FIG.
It can be seen that pseudo color signals such as yellow and cyan appear for pixels such as +3, n+6, n+9, etc., resulting in a decrease in vertical resolution.

On the other hand, in the imaging device shown in FIG. 2, by subtracting the 1H delayed G signal from the real-time G signal by the subtraction circuit 12, the correction signal shown in FIG.
S can be formed. This correction signal ±S is
Derived through the changeover switch circuit 11 every 1H,
The 1H delayed R signal and B signal derived through the switch circuit 9 and the switch circuit 10 are added alternately through the adder circuit 13 and the adder circuit 14. For example, looking at the n+1 horizontal line, the B signal required for the n+1 line uses vertical correlation to transfer the B signal of the n line to the 1H delay line 3, sample hold circuit 6,
It should be extracted via the switch circuit 10. However, in the incident light image of FIG. 3b, there is no B signal component on line n, so B
Can't get signal. Therefore, as mentioned above, n+1
The correction signal +S obtained on the line is added to the adder circuit 14 and outputted from the output terminal 14 as a B signal.
Also, on the n+3 line, the correction signal -S is added to the addition circuit 14.
The B signal of the n+2 line, which is added via the 1H delay signal, is erased.

The correction signal ±S output in response to the luminance signal change portion as described above is converted into a (n+odd number) line signal by the switch circuit 11 as a correction signal to the B signal as shown in FIG. As shown in Figure i, (n+even number) line signals are obtained as correction signals to the R signal, and these signals
is added to the B signal or R signal delayed by 1H. R output signal to which correction signal ±S is added, B
Output signals similar to the incident light image (FIG. 3b) as shown in FIGS. 3i and 3j are obtained.

Further, the correction signal ±S is sent to the adder circuit 18 together with the G signal in FIG.
, and a G signal output similar to the incident light image is formed as shown in FIG. 3k. Output terminal 15,1
The output signals derived from 6 and 17, respectively, are shown in FIG.
The luminance signal (Fig. 3) obtained by combining j and k is as follows:
The generation of false colors is eliminated due to the similarity to the incident light image, and there is no reduction in resolution.

As described above, according to the present invention, in order to obtain horizontal resolution, color filters for G signals, which account for most of the luminance signal, are arranged alternately in the horizontal direction, and red and blue color filters are arranged alternately in the horizontal direction to reduce false color signals in the horizontal direction. In an imaging device that uses a filter array in which filters are arranged alternately in the vertical direction and performs color signal separation using a 1H delay line, a correction signal is formed in advance from a subtracted signal of a predetermined color signal component, and the correction signal is By performing addition processing on each color filter signal to form an output signal using , the generation of false color signals can be suppressed, and a color image with a high vertical resolution equivalent to that obtained when capturing monochrome images can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the arrangement of three color filters in an image sensor, FIG. 2 is a block diagram of an embodiment of the present invention, and FIGS. 3 a to 1 are for explaining the operation of the embodiment of the present invention. FIG. 2 is a combination diagram and signal waveform diagram of a filter arrangement. 2: Image sensor, 3: 1H delay line, 4, 5, 6,
7: Sample hold circuit, 8, 13, 14, 1
8: Addition circuit, 12: Subtraction circuit, 9, 10, 1
1: Switch circuit.

Claims (1)

[Claims] 1. An odd field and an even field formed by aggregating odd lines or even lines of horizontal scanning lines of a two-dimensional solid-state image sensor are used to select a first color for three types of color filters with different sensitive spectral bands. The filters are arranged every other element in the horizontal and vertical directions, and a second color filter and a third color filter are arranged between the first color filters.
In a color imaging device that employs a color filter arrangement in which color filters are arranged alternately in every horizontal row, a real-time signal and a signal delayed by one horizontal scanning period, which is the output of the image sensor that has passed through the first color filter, are subtracted. A correction signal is formed by adding the real-time signal of the image sensor that has passed through the first color filter and the signal delayed by one horizontal scanning period, the output signal of the image sensor that has passed through the second color filter, and the output signal of the image sensor that has passed through the second color filter. The above correction signal is added to each of the output signals of the image sensor that have passed through the color filters No. 3 to form output signals corresponding to each color filter, and the false colors that occur when capturing an image of a subject with large luminance changes in the vertical direction are eliminated. A single-chip color imaging device characterized by erasing.