JPH10285605A - Pixel signal generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the processing time and to enhance the color reproducibility of an image by interleaving pixel signals outputted from an image pickup element to simplify the processing for image display. SOLUTION: A pixel signal outputted from a solid-state image pickup element 11 is given to an analog signal processing circuit 12, where the signal is subjected to a prescribed processing, and the resulting signal is converted into a digital signal at an A/D converter 13. The digital signal given to a color separator 14 is separated into R, G, B signals and stored once in a buffer memory 15, interleaved by a digital signal processing circuit 16, where the signal is converted into a pixel signal whose pixel number is relatively small. A basic pixel signal consisting of a 2×2 pixel matrix includes color signals of all R, G, B colors. The RGB color arrangement is the same as all matrices and G color pixel signals are placed in each matrix on a diagonal line. Thus, the R, B and part of G pixel signals are used without processing for R, G, B pixel signals in one extracted matrix pixel signal corresponding to a 2×2 matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pixel signal generating apparatus for generating an image to be displayed on a screen of a display device by thinning out pixel signals output from an image sensor.

[0002]

2. Description of the Related Art Conventionally, a red (R), green (G) or blue (B) color filter element is provided above each photodiode as an image sensor for generating a pixel signal of a color image. It is known that a pixel signal of R, G or B is obtained by the following. That is, R, G, or B pixel signals are obtained for one pixel. For example, for a G pixel signal in a pixel from which an R pixel signal is obtained, a signal processing circuit
It is obtained by interpolating a plurality of adjacent G pixel signals.

[0003]

When an image obtained by such an image sensor is displayed by a monitor device having a relatively small number of pixels, the number of pixels obtained by the image sensor is reduced by the number of pixels of the monitor device. To match, pixel signals obtained by the interpolation processing in the signal processing circuit are thinned out. As described above, since the thinning processing is performed after the interpolation processing, the processing required for image display by the monitor device is complicated, and the color reproducibility in the image display by the monitor device is deteriorated by performing the interpolation processing. There is.

An object of the present invention is to simplify the processing for displaying an image by a monitor device as much as possible to shorten the processing time and to improve the color reproducibility of an image.

[0005]

A pixel signal generating apparatus according to the present invention is provided with an image sensor capable of obtaining an image composed of a large number of pixels arranged in a lattice, and provided on a light receiving surface of the image sensor. Red (R), green (G), and blue (B) color filter elements provided at positions corresponding to the respective pixels, and m × n read from the image sensor.
Means for generating R, G, B color pixel signals corresponding to one pixel based on pixel signals of a matrix (where m and n are positive integers). 2 are arranged so that each of the R, G, and B color filter elements is included in the matrix of 2. The color pixel signal generating means converts at least the R and B color pixel signals from the pixel signals of the m × n matrix. It is characterized in that the extracted pixel signals are used as they are.

[0006] Preferably, the color pixel signal generating means is m
A color pixel signal is generated based on pixel signals of a 2 × 2 matrix located at a corner in a × n matrix.

The color pixel signal generating means may directly use the pixel signals extracted from the m × n matrix pixel signals for the G color pixel signals.

The color pixel signal generating means may take an arithmetic mean of two pixel signals extracted from an m × n matrix of pixel signals for the G color pixel signal.

Preferably, m and n in an m × n matrix
Are equal.

The color pixel signal generating means is, for example, 2 × 2
A color pixel signal is generated based on the pixel signals of the matrix. The color pixel signal generating means is, for example, 3 × 3
A color pixel signal is generated based on the pixel signals of the matrix. Further, the color pixel signal generating means is, for example, 4 ×
A color pixel signal is generated based on the pixel signals of the matrix No. 4.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an electrical configuration of a pixel signal generation device according to an embodiment of the present invention.

The system control circuit 24 has a microprocessor, and controls the entire device. The solid-state imaging device 11 is arranged on the optical axis of a photographic optical system (not shown), and an image composed of a large number of lattice-like pixels obtained by the photographic optical system is formed on a light receiving surface of the solid-state imaging device 11. A red (R), green (G) or blue (B) color filter element is provided at a position corresponding to each pixel on the light receiving surface.

The pixel signal output from the solid-state imaging device 11 is subjected to predetermined processing in an analog signal processing circuit 12 and then converted into a digital signal by an A / D converter 13. The digital pixel signals read out line-sequentially from the A / D converter 13 are output to the color separation device 14 by R,
After being sorted for each of G and B, and once stored in the buffer memory 15, it is input to the digital signal processing circuit 16.
This pixel signal (hereinafter, referred to as a basic pixel signal) is thinned out in the digital signal processing circuit 16 and converted into a pixel signal having a relatively small number of pixels (hereinafter, referred to as an extracted pixel signal). This thinning process will be described later.

The extracted pixel signal output from the digital signal processing circuit 16 is transferred to an image display device (monitor device) 21 having, for example, a liquid crystal display device, and an image is displayed on a screen. The extracted signal output from the digital signal processing circuit 16 is sent to the memory card controller 17, is replaced with a predetermined format, and is recorded on the memory card. Further, the extracted signal is converted into a signal corresponding to an external device in the interface circuit 19 according to the command signal output from the system control circuit 24, and is output from the output terminal 20 to the outside.

An operation unit 22 and a display unit 23 are connected to the system control circuit 24. The operation unit 22 displays an image (extracted pixel signal) displayed by the image display device 21.
And a switch for selecting a reduction ratio that is a ratio of the number of pixels of the image (basic pixel signal) obtained by the solid-state imaging device 11 to the number of pixels. The display unit 23 is provided with a liquid crystal display element or the like for displaying an operation mode or the like of a camera provided with the pixel signal generation device.

FIG. 2 shows an example of the configuration of a color filter provided on the light receiving surface of the solid-state imaging device 11, that is, an example of an arrangement of color filter elements. This arrangement is called a Bayer arrangement, in which among the three primary colors of R, G, and B, the G color filter elements 26 that most affect the luminance are arranged in a checkered pattern, and the other two colors are arranged in the gaps. It is. That is, the colors of the adjacent color filter elements are different from each other, and the G color filter elements 26 are provided every other in the vertical direction and the horizontal direction. In one row F1 extending in the horizontal direction, an R color filter element 25 is provided between two G color filter elements 26. In a row F2 located above and below this row F1,
A B color filter element 27 is provided between the two G color filter elements 26.

Next, the image corresponding to the basic pixel signal is divided by 1 /
A thinning-out process for reducing an image into (n × n) images will be described. First, the simplest case of n = 2 thinning will be described. FIG. 3 shows a relationship between an array of basic pixel signals read from the image sensor 11 provided with the color filter shown in FIG. 2 and an extracted pixel signal in an image reduced to 1 / (2 × 2). Here, a case will be described in which all of the R, G, and B extracted pixel signals are directly used from the basic pixel signals.

The basic pixel signals of the 2 × 2 matrix surrounded by the thick line S1 all include R, G and B color signals. The arrangement relationship of these colors is the same in all the matrices, and the G color pixel signals are at diagonal positions. Therefore, the pixel signal marked with a circle is adopted as it is without processing, and 2 × 2
R of one extracted pixel signal corresponding to the matrix S1 of
G and B pixel signals can be used.

The thinning process shown in FIG. 3 is compared with the conventional example shown in FIG. As shown in FIG. 4, conventionally, a certain pixel (for example, R1) is adopted as it is without processing an R pixel signal. On the other hand, for the G pixel signal, the arithmetic mean of the four pixel signals (G1) located at the top, bottom, left, and right is taken, and for the B pixel signal, the arithmetic mean of the four pixel signals (B1) located at an oblique direction is calculated. As a result, pixel signals of R, G, and B in the pixel are obtained. Similarly, for the B2 pixel, the B pixel signal is used as it is, and the R and G pixel signals are obtained by taking the arithmetic mean of the surrounding pixel signals. For the G3 pixel, the G pixel signal is employed as it is, and the R and B pixel signals are obtained by taking the arithmetic mean of the surrounding pixel signals. Thus, the generated color pixel signal is
Any two of R, G, and B are obtained by interpolation.

Comparing the embodiment of the present invention shown in FIG. 3 with the conventional example shown in FIG. 4, the interpolation processing, that is, the processing for taking the arithmetic mean has been conventionally performed, whereas the embodiment of FIG. No interpolation is performed. As described above, since the interpolation process is not included in the generation of the extracted pixel signal, according to the present embodiment, the time for the thinning process is short, and the display device 2
1 reproduces an image with improved color reproducibility.

FIG. 5 shows one image corresponding to the basic pixel signal.
A thinning process for reducing an image to / (4 × 4) is shown. The basic pixel signals of the 4 × 4 matrix surrounded by the thick line S2 all include R, G, and B color signals. The arrangement relationship of these colors is the same in all matrices. Also, the 2 × 2 matrix (dashed line S3) located at the left corner of each matrix S2 has R, G
And B color signals are included, and the arrangement relationship of these colors is the same, and the G color pixel signal is at a diagonal position. Therefore, the pixel signals marked with a circle are adopted as they are without processing, and the 2 × 2 matrix S1
R, G, and B pixel signals of one extracted pixel signal corresponding to. That is, the example shown in FIG. 5 provides the same effect as the example shown in FIG.

FIG. 6 shows one image corresponding to the basic pixel signal.
A thinning process for reducing the image to / (3 × 3) is shown. The basic pixel signals of the 3 × 3 matrix surrounded by the thick line S4 all include R, G, and B color signals. The arrangement relationship of these colors is the same in all matrices. Also, the 2 × 2 matrix (broken lines S5, S6) located at the left corner of each matrix S4
Although the R, G, and B color signals are included, the arrangement of these colors is different between the matrices S5 and S6. That is, the G color pixel signal is located at the upper left and lower right in the matrix S5, but is located at the upper right and lower left in the matrix S6. Therefore, the pixel signal (○
(Marked) indicates that the matrix G in the matrix S5
, B pixel signals and the lower R pixel signals, and in the matrix S6, the upper B pixel signals and the lower G and R pixel signals. According to the example of FIG.
The same effects as in the examples of FIGS. 3 and 5 can be obtained.

FIG. 7 shows another embodiment of the present invention. The basic pixel signals of the 2 × 2 matrix T1 include:
Although the R, G, and B color signals are included, in this embodiment, the G color pixel signals having a diagonal positional relationship are arithmetically averaged, and the R and B pixel signals are processed. Adopt it without any change.

Similarly, the basic pixel signals of the 3 × 3 matrix T2 are arithmetically averaged for the G color pixel signals having a diagonal positional relationship, and the R and B pixel signals are not processed. Adopt as it is. 4x4
The same applies to the pixel signals of the matrix T3.

According to this embodiment, the interpolation processing is performed on the G pixel signal, so that the processing time is longer due to the more arithmetic processing compared to the examples of FIGS. Compared to, the process is simpler,
Processing time is short.

FIG. 8 shows an example of a flowchart of a program for executing a process for displaying an image by the image display device 21 and a process for recording the image on the memory card 18.

In step 101, the reduction rate N is set to the initial value 1
Is set to In step 102, it is determined whether or not the reduction ratio N is the same size (N = 1). If N = 1, the normal interpolation mode is selected in step 103, and the extracted pixel signal is obtained without thinning out the basic pixel signal. If N is not 1, 1
The mode is changed to the reduction mode of / (N × N), and the thinning process shown in FIG. 3 and any of FIGS.

In step 105, an image is displayed by the display device 21 in accordance with the extracted pixel signal obtained in step 103 or 104. In step 106, the reduction rate N is determined based on the image displayed on the display device 21.
Is determined to be acceptable. When it is determined that the reduction ratio N is inappropriate, step 107 is executed, a new reduction ratio N is input, and the process returns to step 102. When the reduction ratio N is appropriate, it is determined in step 108 whether or not the image signal should be recorded on the memory card 18. If it should be recorded, step 10
At 9, the basic pixel signal is recorded on the memory card 18, and when it should not be recorded, the program ends without executing step 109.

As described above, according to the embodiment of the present invention,
Since the use of the R, G, and B basic pixel signals as they are while minimizing the use of an interpolation signal containing an error as the pixel signal for the image display device 21, the processing for displaying an image can be shortened. In addition, the color reproducibility is improved when the image is reproduced by the image display device 21.

[0030]

As described above, according to the present invention, the processing for displaying an image by the monitor device can be simplified as much as possible to shorten the processing time and improve the color reproducibility of the image.

[Brief description of the drawings]

FIG. 1 is a block diagram of a camera using a color image sensor according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a configuration of a color filter used for an image sensor.

3 shows an arrangement of basic pixel signals read from an image sensor provided with a color filter shown in FIG. 2 and 1 / (2 ×
FIG. 4 is a diagram showing a relationship between an image reduced in 2) and an extracted pixel signal.

FIG. 4 is a diagram showing an example of a conventional interpolation process.

5 shows an arrangement of basic pixel signals read from an image sensor provided with a color filter shown in FIG. 2 and 1 / (4 ×
FIG. 4C is a diagram illustrating a relationship with an extracted pixel signal in an image reduced in 4).

FIG. 6 shows an arrangement of basic pixel signals read from an image sensor provided with a color filter shown in FIG. 2 and 1 / (3 ×
FIG. 3C is a diagram illustrating a relationship with an extracted pixel signal in an image reduced in 3).

FIG. 7 is a diagram illustrating a relationship between an array of basic pixel signals and an extracted pixel signal in a reduced image according to another embodiment of the present invention.

FIG. 8 is a flowchart of a program for image display and image recording operation.

[Explanation of symbols]

 11 Image sensor 25 R color filter element 26 G color filter element 27 B color filter element

Claims (8)

[Claims] An image pickup device capable of obtaining an image composed of a large number of pixels arranged in a lattice, and a red (R) provided on a light receiving surface of the image pickup device and provided at a position corresponding to each pixel. ), Green (G) and blue (B) color filter elements, and mxn (where m, n
Means for generating R, G, B color pixel signals corresponding to one pixel on the basis of pixel signals of a matrix of (a positive integer), wherein the color filter elements are arranged in a 2 × 2 matrix. R, G, and B color filter elements are arranged so as to be included, and the color pixel signal generating means extracts, for at least the R and B color pixel signals, pixels extracted from the m × n matrix pixel signals. A pixel signal generation device characterized by using a signal as it is. 2. The method according to claim 2, wherein the color pixel signal generating means includes
2. The pixel signal generation device according to claim 1, wherein the color pixel signal is generated based on pixel signals of a 2 × 2 matrix located at a corner in a × n matrix. 3. The pixel according to claim 1, wherein said color pixel signal generation means adopts, as a G color pixel signal, a pixel signal extracted from the m × n matrix of pixel signals as it is. Signal generator. 4. The color pixel signal generating means calculates an arithmetic mean of two pixel signals extracted from the m × n matrix of pixel signals for a G color pixel signal. 3. The pixel signal generation device according to 1. 5. The pixel signal generation device according to claim 1, wherein the values of m and n in the m × n matrix are equal. 6. The color pixel signal generation means according to claim 2, wherein:
The pixel signal generation device according to claim 5, wherein the color pixel signal is generated based on pixel signals of the matrix of (1). 7. The color pixel signal generation means according to claim 3, wherein:
The pixel signal generation device according to claim 5, wherein the color pixel signal is generated based on pixel signals of the matrix of (1). 8. The color pixel signal generation means according to claim 4, wherein
The pixel signal generation device according to claim 5, wherein the color pixel signal is generated based on pixel signals of the matrix of (1).