KR102392711B1 - Color camera and method for acquiring color image thereof - Google Patents

Abstract

In a color camera in which a plurality of pixels are arranged in an array form, at least some of the plurality of pixels each receive a color filter that outputs only a corresponding color signal from an optical signal input through a lens, and a color signal output from the color filter. a sensor for converting an electrical signal, and a hologram mask positioned above the color filter and diffracting an optical signal of a color different from the color corresponding to the color filter from the optical signal to adjacent color pixels of the corresponding color.

Description

COLOR CAMERA AND METHOD FOR ACQUIRING COLOR IMAGE THEREOF

The present invention relates to a color camera and a color image acquisition method thereof, and more particularly, to a color camera capable of increasing the amount of light reaching each sensor without increasing the pixel size of the sensor and an image acquisition method thereof.

A conventional camera acquires an image by converting the intensity of input light into an electrical signal.

As a method for obtaining a color image, a method using a Bayer method is the most used. In this case, the color filter formed on the sensor corresponding to each optical element passes only the corresponding color, so that the amount of light from the corresponding pixel is used as a value for a specific color. For each color, only the pixels corresponding to 1/4 or 1/2 of the total pixels have the actual color value, and pixels without the remaining color fill the value through interpolation from the color channel of the adjacent pixel. . In this case, from the viewpoint of each color image, only 1/4 or 1/2 of the light that actually enters the entire camera is transmitted to the sensor. Therefore, in the case of an environment in which external lighting is dark, the image quality is deteriorated or noise is severely generated. In order to solve this problem, there is a method of increasing the amount of light received by each pixel by increasing the area of the sensor itself, but there may be problems such as an increase in the camera itself, a problem in manufacturing cost, and an increase in power consumption. . In addition, there is a problem in that it is difficult to apply in a miniaturized system such as a portable camera.

An object of the present invention is to provide a color camera capable of increasing the amount of light reaching each sensor without increasing the pixel size of the sensor and a method for acquiring a color image thereof.

According to one embodiment of the present invention, there is provided a color camera in which a plurality of pixels are arranged in an array form. At least some of the pixels of the color camera each have a color filter that outputs only a corresponding color signal from an optical signal input through a lens, a sensor that converts a color signal output from the color filter into an electrical signal, and the color and a hologram mask disposed on the filter and diffracting an optical signal of a color different from the color corresponding to the color filter from the optical signal to adjacent color pixels of the corresponding color.

The at least some pixels may include a red filter, a green filter, and a blue filter, and the remaining pixels among the plurality of pixels may be infrared pixels for obtaining an infrared image.

The at least some pixels may be arranged in a Bayer pattern in which a red filter, a green filter, and a blue filter have a ratio of 1:2:1.

A hologram mask mounted on the red filter, the green filter, and the blue filter, respectively, may diffract an infrared component and transmit it to the infrared filter.

Each of the at least some pixels may further include a waveguide disposed to transmit an optical signal between the hologram mask and the color filter.

The hologram mask of one pixel may be located on different layers with the hologram mask of an adjacent pixel and the waveguide interposed therebetween.

The hologram mask positioned above the waveguide may be of a reflective type, and the hologram mask positioned below the waveguide may be of a transmissive type.

A hologram mask of one pixel may diffract a wavelength of a different color from that of a hologram mask of an adjacent pixel.

According to another embodiment of the present invention, there is provided a color image acquisition method of a color camera in which a plurality of pixels are arranged in an array form. The color image acquisition method comprises the steps of: transmitting, by a hologram mask of each pixel, an optical signal having the same color as that of the corresponding pixel from an input optical signal and diffracting the optical signal of a different color to adjacent pixels of the corresponding color; outputting, by a color filter, only the signal of the corresponding color received from the hologram mask to the sensor of each pixel, and converting, by the sensor of each pixel, the signal of the received color into an electrical signal.

Each of the pixels may further include a waveguide formed on the color filter of each pixel.

The waveguide may be formed between the color filter of each pixel and the hologram mask of each pixel.

The hologram mask of at least one pixel may be positioned on different layers with the hologram mask of an adjacent pixel and the waveguide interposed therebetween.

A hologram mask of one pixel may diffract a wavelength of a different color from that of a hologram mask of an adjacent pixel.

According to an embodiment of the present invention, the amount of light reaching each sensor is increased without increasing the pixel size of the sensor of the camera to have the effect of having a larger aperture, thereby increasing the image quality. .

1 and 2 are diagrams for explaining the structure of a conventional color camera.
FIG. 3 is a view for explaining a color image display method of the color camera shown in FIG. 1 .
4 is a diagram schematically illustrating a structure of a color camera according to an embodiment of the present invention.
5 is a diagram illustrating a light transmission path in a color camera according to an embodiment of the present invention.
6 is a diagram illustrating an example of using a different hologram mask according to each color pixel.
7 and 8 are views showing different hologram masks of two layers, respectively.
9 is a diagram illustrating a structure of a color camera according to another embodiment of the present invention.
FIG. 10 is a diagram illustrating a light transmission path in the color camera shown in FIG. 9 .

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be implemented in several different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification and claims, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless specifically stated to the contrary.

Now, a color camera and a method for obtaining a color image thereof according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 and 2 are diagrams for explaining the structure of a conventional color camera.

Referring to FIG. 1 , in the Bayer type color camera, the color filter layer 20 is formed on the sensor layer 10 .

The color filter layer 20 includes a color filter array in which the color filters 21 , 23 , and 25 are arranged according to a Bayer pattern. The color filters 21 , 23 , and 25 may include, for example, a red filter (R), a green filter (G), and a blue filter (B). In the Bayer pattern, the red filter (R), the green filter (G), and the blue filter (B) have a ratio of 1:2:1, and the red filter (R) and the blue filter (B) are arranged in a diagonal direction, and Two green filters (G) are disposed in a diagonal direction that intersects.

The red filter (R), the green filter (G), and the blue filter (B) filter the optical signal input through a lens (not shown), respectively, and transmit color signals having a wavelength corresponding to each color to the sensor ( 11, 13, 15).

The sensor layer 10 may include sensors 11 , 13 , and 15 formed to correspond to the color filters 21 , 23 , and 25 . Each of the sensors 11 , 13 , and 15 converts a color signal output from the color filters 21 , 23 , and 25 into an electrical signal.

In this case, one color filter and one sensor may form one color pixel, and one color pixel performs an operation of obtaining a pixel image for a corresponding color. For example, a red filter (R) and a corresponding sensor 11 form a red pixel, a red filter (R) and a corresponding sensor 11 form a red pixel, and a green filter (G) and The corresponding sensor 13 forms a green pixel, and the blue filter B and the corresponding sensor 15 form a blue pixel.

FIG. 3 is a view for explaining a color image display method of the color camera shown in FIG. 1 .

Referring to FIG. 3 , in the existing Bayer type color camera, only pixels corresponding to 1/4 or 1/2 of all pixels for each color have actual color values. A pixel having an actual red or blue color corresponds to 1/4 of all pixels, and a pixel having an actual green color corresponds to 1/2 of all pixels.

In this case, the remaining pixels without color have color values through interpolation from the corresponding color channels of adjacent pixels.

In such a Bayer type color camera, since only 1/4 or 1/2 of the light that actually enters the camera is transmitted to the sensors 11, 13, and 15, image quality may deteriorate or noise may be severely generated.

According to an embodiment of the present invention, a color camera capable of increasing the amount of light reaching each sensor without increasing the pixel size of the sensor is proposed.

4 is a diagram schematically illustrating a structure of a color camera according to an embodiment of the present invention.

Referring to FIG. 4 , in a color camera according to an embodiment of the present invention, a color filter layer including color filters 121 , 123 , and 125 is formed on a sensor layer including sensors 111 , 113 , and 115 , , hologram masks 141 and 145 are formed on the color filter layer. In addition, a thin waveguide 130 may be formed between the hologram masks 141 and 145 and the color filter layer for a light transmission path. In general, since green has a wide wavelength, FIG. 4 shows that the hologram masks 141 and 145 are formed on the red filter R and the blue filter B, but the red filter R and the green filter (G) and blue filter (B) A hologram mask may be formed on one or more color filters. For example, a hologram mask may be formed on the red filter (R), the green filter (G), and the blue filter (B). The hologram mask may be directly formed on the color filter layer without the waveguide, or the hologram mask may be formed on the color filter layer with the waveguide placed thereon. Also, a waveguide having a hologram mask function may be formed on the color filter layer.

When light of a color different from the color of the corresponding color filters 121 and 125 is incident, the hologram masks 141 and 145 diffract light of a different color (eg, green) to filter the color filter ( For example, a green filter). This has the effect of increasing the effective area of each color pixel.

That is, when light is incident on the hologram masks 141 and 145 , the light of the corresponding color is diffracted according to the wavelength selectivity of the hologram masks 141 and 145 , and the light to be rotated is transmitted to the corresponding color filter according to the diffraction angle. do. At this time, the wavelength of the unselected color passes through the hologram masks 141 and 145 as it is and is transmitted to the corresponding color filter.

The hologram masks 141 and 145 may be manufactured using a diffraction grating device such as a general DOE (Diffractive Optic Elements) or HOE (Holographic Optic Elements).

5 is a diagram illustrating a light transmission path in a color camera according to an embodiment of the present invention.

Referring to FIG. 5 , the hologram masks 141 and 145 formed on the red filter R and the blue filter B may transmit green light to the green filter G by diffracting the green light according to wavelength selectivity.

On the other hand, in the case of the existing Bayer type color camera, each color filter blocks other color signals, so that other color signals are not transmitted to the sensor.

As such, when the hologram masks 141 and 145 are used, the effective area of the green pixel is increased without increasing the pixel size as indicated by the dotted line.

The efficiency of light transmitted to the sensors 111 and 113 varies according to the diffraction angle of the hologram masks 141 and 145 and the thickness of the waveguide 130 . In the case of the diffraction angles of the hologram masks 141 and 145, Equation 1 may be defined on the assumption that only the first-order diffracted light is used.

Here, θ represents the diffraction angle of the hologram mask, λ represents the wavelength of light, and d represents the spacing between the diffraction gratings.

According to Equation 1, the spacing d of the diffraction grating is determined according to the diffraction angle θ and the wavelength λ.

6 is a diagram illustrating an example of using a different hologram mask according to each color pixel.

As shown in FIG. 6 , a hologram mask 143 may be formed on the green filter G as well. At this time, unlike the hologram masks 41 and 145 , the hologram mask 143 diffracts red light and transmits it to the adjacent red filter R.

For example, the hologram masks 141 and 145 corresponding to the red pixel and the blue pixel diffract only green light and transmit it to the green filter 123 of the adjacent green pixel, and the hologram mask 143 corresponding to the green pixel is Only red light is diffracted and transmitted to the red filter 121 of the adjacent red pixel.

In addition, in order to reduce the thickness of the waveguide 130 and increase the effective area of the pixel, a hologram mask of two or more layers may be used.

7 and 8 are views showing different hologram masks of two layers, respectively.

7 and 8 , different hologram masks 141 and 145/143 ′ may be positioned on different layers with the waveguide 130 interposed therebetween.

It is assumed that the primary hologram masks 141 and 145 corresponding to the red pixel and the blue pixel diffract only green light and transmit it to the green filter 123 of the adjacent green pixel. The hologram masks 143 ′ and 143 corresponding to green pixels may transmit only green light, transmit only green light, and reflect light of other colors in different directions, depending on a manufacturing method.

In this case, when the hologram masks 141 and 145/143 ′ are transmissive hologram masks, the primary hologram masks 141 and 145 corresponding to the red pixel and the blue pixel are disposed above the waveguide 130 as shown in FIG. 7 . The secondary hologram mask 143 ′ corresponding to the green pixel may be positioned below the waveguide 130 .

On the other hand, when the hologram masks 141 and 145/143' are reflective hologram masks, as shown in FIG. 8 , the primary hologram masks 141 and 145 corresponding to the red pixels and blue pixels are of the waveguide 130 . The secondary hologram mask 143 ′ located at the lower portion and corresponding to the green pixel may be located above the waveguide 130 .

At this time, the primary hologram masks 141 and 145 diffract light of each color according to the total reflection condition of the waveguide 130, and the direction of the reflected light along the waveguide 130 is changed in the secondary hologram mask 143, It is passed to the corresponding color pixel.

9 is a diagram illustrating a structure of a color camera according to another embodiment of the present invention, and FIG. 10 is a diagram illustrating a light transmission path in the color camera illustrated in FIG. 9 .

The camera shown in FIG. 9 is an RGB-IR (Infrared Ray) camera, and is configured by changing one green pixel to an IR pixel in a bare-type color camera. The IR pixel may be composed of an IR filter that filters and outputs only an IR signal among optical signals input through a lens (not shown), and an IR sensor that converts an IR signal passing through the IR filter into an electrical signal.

In such an RGB-IR camera, a visible light image is obtained through a red pixel, a green pixel, and a blue pixel, and an infrared image is obtained through an IR pixel. That is, the RGB-IR camera is composed of a combination of a red pixel, a green pixel, a blue filter, and an infrared pixel.

Referring to FIG. 10 , even in the RGB-IR camera, by mounting a hologram mask on a red pixel, a green pixel, and a blue pixel, the infrared component from the hologram mask of the red pixel, the green pixel, and the blue pixel can be diffracted and collected in the IR sensor. there is. In this way, it is possible to increase the optical efficiency of the IR image, thereby reducing noise, which is a problem in the infrared image.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. is within the scope of the right.

Claims (13)

A color camera in which a plurality of pixels are arranged in an array form,
At least some of the pixels among the plurality of pixels are each
A color filter that outputs only the corresponding color signal from the optical signal input through the lens;
a sensor for converting a color signal output from the color filter into an electrical signal;
a hologram mask positioned above the color filter and diffracting an optical signal of a color different from the color corresponding to the color filter from the optical signal to an adjacent color filter; and
a waveguide disposed on the color filter
including,
A hologram mask of any one pixel among the at least some pixels is located above the waveguide, and a hologram mask of a pixel adjacent to the at least one pixel is located below the waveguide. In claim 1,
The at least some pixels include a red filter, a green filter, and a blue filter, and the remaining pixels of the plurality of pixels are infrared pixels for obtaining an infrared image. In claim 1,
wherein the at least some pixels are arranged in a Bayer pattern in which a red filter, a green filter, and a blue filter have a ratio of 1:2:1. In claim 2,
The hologram mask mounted on the red filter, the green filter, and the blue filter, respectively, diffracts the infrared component and transmits it to the infrared pixel. delete delete In claim 1,
The hologram mask positioned above the waveguide is a reflective type, and the hologram mask located below the waveguide is a transmissive type color camera. In claim 1,
The hologram mask of any one pixel diffracts a wavelength of a different color from that of the hologram mask of the adjacent pixel. A method for obtaining a color image of a color camera in which a plurality of pixels are arranged in an array, comprising:
The hologram mask of each pixel transmits an optical signal of the same color as the color of the corresponding pixel from the input optical signal and diffracts the optical signal of a different color to adjacent pixels;
outputting, by the color filter of each pixel, only the signal of the corresponding color received from the hologram mask to the sensor of each pixel; and
converting, by the sensor of each pixel, the received color signal into an electrical signal
including,
Each pixel further includes a waveguide formed above the color filter of each pixel,
A hologram mask of some pixels among the plurality of pixels is located above the waveguide, and a hologram mask of pixels adjacent to the some pixels is located below the waveguide. delete delete delete In claim 9,
The hologram mask of the partial pixel diffracts a wavelength of a color different from that of the hologram mask of the adjacent pixel.

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