JPH06350904A - Camera - Google Patents

Abstract

PURPOSE:To make the size of a camera small by providing a color aberration correction which reads a color picture element output stored in a memory device so as to correct chromatic aberration of an optical system to the camera thereby avoiding a large size chromatic aberration correction optical system. CONSTITUTION:Each output from A/D converters 4A-4D is subjected to prescribed image pickup processing such as gamma processing, aperture processing and color separation processing by image pickup process sections 5A-5D and the read/write of each result is controlled by using a field memory control section 12. Then interpolation processing sections 7A, 7B, 7C, 7D applying interpolation processing to outputs of memories 6A-6D are provided and an interpolation coefficient generating section 13 generates interpolation coefficients KX, KY or the like. An interpolation output is selected by a changeover switch 8 and given to an encoder 9. Then a signal encoded by the encoder 9 is converted into an analog signal at a D/A converter 10 and the resulting signal is provided as an analog signal subjected to chromatic aberration processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, and more particularly to a camera for correcting chromatic aberration.

[0002]

2. Description of the Related Art An image sensor (CCD) having a relatively small number of pixels
Etc.), each image pickup element is made to share each divided area obtained by dividing one image, and the images obtained by the plurality of image pickup elements are combined to obtain a high-quality (multi-pixel) image. like,
A so-called bonded image pickup device has been proposed.

For example, as shown in FIG. 10, one image G is vertically and horizontally (lower right G1, lower left G2, upper right G3,
The image is divided into four areas (upper left G4), and the image in each area is output by the corresponding image sensor. Such a divided image is obtained by using a plurality of known prisms as shown in FIG. 11, for example. The transmitted light and the reflected light of the prisms arranged as shown in FIG. 11 are appropriately selected, the incident light image (optical image) G is divided into the above-mentioned four regions, and four image pickup elements are arranged appropriately. Each of the divided images is received by each of I1 to I4. Color pixels are arranged on each image pickup element to obtain a color image.

[0004]

As described above, in the conventional camera, a plurality of image pickup elements are attached so that the image circle of the optical system in which the optical path is divided into a plurality of portions can be received and the output of each image pickup element is output. The signals are combined to generate one high-definition image. However, in such an apparatus, a large image circle is required for the optical system with respect to the size of the effective area of the image sensor to be used, and therefore the chromatic aberration compensating optical system also becomes large and the apparatus becomes large. There is a problem that it ends up.

SUMMARY OF THE INVENTION An object of the present invention is to provide a camera using a plurality of image pickup elements, which is capable of electrically correcting chromatic aberration and downsizing the apparatus.

[0006]

In order to solve the above-mentioned problems, the camera according to the present invention divides a color image display screen area having a predetermined number of pixel arrays in the horizontal and vertical directions into a plurality of areas. A plurality of color image pickup elements arranged at respective predetermined positions to cover the generation of partial images corresponding to the respective partial areas, and color pixel outputs arranged on the plurality of color image pickup elements, and the arrangement positions of those pixels. And a chromatic aberration correcting means for reading out the color pixel output stored in the memory means by calculating so as to correct the chromatic aberration of the optical system. To be done.

[0007]

In the present invention, the color image display screen area is divided into a plurality of areas, and the chromatic aberration of the optical system is corrected by calculating the color pixel outputs arranged on the plurality of color image pickup devices corresponding to the respective divided areas.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of a camera according to the present invention. Referring to the drawing, four (four) image pickup devices (CCDs) 2A, 2B, 2C and 2D each having an optical low pass filter (LPF) 1A, 1B, 1C and 1D on the input side are respectively The image areas of the upper left portion, the upper right portion, the lower left portion, and the lower right portion, which are obtained by dividing a single image vertically and horizontally, are shared, and the output of each image sensor driven by the TG (timing generator) 11 is the S / H & AGC portion. After being sample-held in 3A to 3D and AGC (automatic gain control), A /
It is converted into a digital signal by the D converters 4A to 4D.

Outputs from the A / D converters 4A to 4D are subjected to predetermined image pickup processes such as γ processing, aperture processing, and color separation processing in the image pickup processing units 5A to 5D, and the respective field memories 6A to 5D. It is stored in 6D. Writing and reading of the field memories 6A to 6D are controlled by control signals from the memory control unit 12. The memory control unit 12 controls reading and writing of the field memories 6A to 6D provided for the four image pickup devices. Interpolation processing units 7A, 7B, 7C and 7D are provided for performing interpolation processing on the outputs of the field memories 6A, 6B, 6C and 6D. Interpolation coefficients (Kx, Ky, etc.) used for this interpolation processing
Is generated from the interpolation coefficient generator 13. Changeover switch 8
Switches the outputs from the interpolation processing units 7A to 7D and outputs the output to the encoder 9. The signal encoded by the encoder 9 is converted into an analog signal by the D / A converter 10 and output as a video output.

FIG. 2 shows a detailed block diagram of the imaging process circuits 5A to 5D in the embodiment shown in FIG. A
The digital image data sent from the / D converters (4A to 4D) are processed by the luminance signal processing system Y and the color signal processing system C, respectively, and then the corresponding field memories 6A to
Recorded in each of 6D. That is, the image data has a color carrier component removed by a low-pass filter (LPF) 51, delayed by 1H for time adjustment with a color processing system by a 1H delay unit 52, and then a γ correction unit 53 for monitor display.
The .gamma.-correction processing is performed in step (1), and the aperture correction processing is performed in the aperture correction section 54, and then the result is recorded in the corresponding field memory.

On the other hand, in the color signal processing system, the image data is
The bandpass filter (BPF) 55 extracts the modulated color components, and the color separation unit 56 performs color separation processing. Then, the primary color generation unit 57 performs R, G, and
A B primary color component is generated. The generated primary color components have their respective primary color component levels corrected by the white balance unit 58 in accordance with the type and state of the light source, and then subjected to the γ process by the γ processing unit 59 to obtain the respective primary colors R, G, B. Signal is recorded in the corresponding field memory.

The primary color generation processing in the primary color generation unit 57 will be described with reference to FIGS. 3 and 4. FIG. 3 is an operation explanatory diagram of a single-plate color imager in which each complementary color filter is stretched in a checkered pattern for a 16-pixel configuration for simplification of description.
As shown in the figure, pixel readout is A1 in the A field.
And A2, the charges accumulated in the upper and lower pixels are mixed and read. Each mixed pixel data is transferred to the horizontal shift register Hreg and read in the reading direction of the arrow. Therefore, the horizontal shift register H
The order of signals output from reg is [G
+ Cy], [Mg + Ye], [G + Cy], [Mg + Y]
e]. Here, each of the filters Cy, Ye, Mg
With respect to the output signal of the pixel having G and G, each of the green (G), blue (B), and red (R) primary color components has the following configuration. Cy = G + B Ye = R + G Mg = R + BG G = G Therefore, when the signal output from Hreg is used, the luminance signal YL and the color (chroma) signal C are added next to each other as follows, and the chroma signal is reduced. It is obtained by That is, the signal YL uses an approximate signal of YL = {(G + Cy) + (Mg + Ye)} = 2B + 3G + 2R, and the signal C1 uses an approximate signal of C1 = {(Mg + Ye)-(G + Cy)} = 2R-G.

Next, considering the A2 line, the signals from the horizontal shift register Hreg are (Mg + Cy), (G + Ye), (Mg + Cy), (G
+ Ye) are output in this order. When the signal YL is formed by this signal, YL = {(G + Ye) + (Mg + Cy)} = 2B + 3G + 2R, which is the same as the A1 line. Similarly, the chroma signal C2 is approximated by C2 = {(G + Ye)-(Mg + Cy)} =-(2B-G). That is, the chroma signal is line-sequential, and (2R-G) and-(2B-G) can be taken out alternately. The same applies to the B field.

Each line (n-1, n, n + 1 ... Line)
The signals YL, C1 and C2 for are shown in FIG. In FIG. 4, paying attention to the n line, since the signal C1 is not obtained in this line, this signal is generated by the interpolation process using the upper and lower lines (n-1 line and n + 1 line). Thus, the signals YLn, C of the n line
1n and C2n are obtained, and eventually the signals YL, C1 and C2 are expressed as follows. YL = 2R + 3G + 2B C1 = 2R-G C2 =-(2B-G) When this simultaneous equation is solved for R, G and B, the primary color signals R, G and B are R = (YL + 4C1 + C2) / 10 G = (YL-C1 + C2) ) / 5 B = (YL-C1 + 4C2) / 10.

Now, as described above, the field memories 6A-
The reading of the R, G, B signals recorded in 6D is performed by using the read address generated in consideration of the chromatic aberration as follows. In FIG. 5A, the image forming (photographing) area of the copy is divided into four vertically and horizontally (area 1 to area 4), and each area is divided into 4 areas.
It shows the coordinate area when they are associated with each other by the imager, and the distance r from the origin of the intersection of the optical axis and the image plane, that is, the origin 0.
The point image that should be imaged at point B is dispersedly imaged at points determined along the straight line OB according to each color wavelength due to chromatic aberration. At this time, since red shifts inward and blue shifts outward, for example, in the point image that should be imaged at point B, the red point is at point A (r _R ) and the blue point is at point C (r _B ). It will form an image.
Here, r _R and r _B can be approximated by the following linear expression. r _R = r (1 + S _R ) r _B = r (1 + S _B ) Here, S _R and S _B depend on the lens state such as the focal length of the lens and are expressed by the following equation. S _R = C _R + D _R f S _B = C _B + D _B f Here, C _R , C _B , D _R and D _B are constants determined by the lens, and f is a constant indicating the focal length.

Position pixel data determined for each color signal is read from the field memory in consideration of a shift caused by chromatic aberration based on the above approximate expression. FIG. 5B shows a principle diagram for obtaining pixel data at points A, B, and C in FIG. 5A. In the figure, white circles represent the pixel data stored in the field memory, the red (R) signal is the pixel data at the point A, and this pixel data is the four red (R) pixel data A1 around it. Obtained by interpolation processing using A4. Similarly, the blue (B) signal is the pixel data at the point C, and four surrounding blue (B) pixel data C1 to C4.
It is obtained by interpolation processing using. The green (G) signal uses the pixel data itself at point B.

Next, a method of generating an address when reading image data from each field memory will be described.
In FIG. 5A, a thick solid line frame indicates an effective imaging area, that is, a display area. On the other hand, mechanically mounting the imager at an ideal mounting position is
It is very difficult and causes a shift or tilt in the coordinate axis direction, so it is necessary to perform coordinate conversion to compensate for this shift. In FIG. 6, O is the optical axis, OD is the display coordinate origin, On is the origin of the imager n, point P is the image formation position when there is no chromatic aberration,
The point PA indicates the actual image forming position. Performing coordinate conversion means that the position (X,
The position (x ', y') of the point PA shown in the coordinate system of the imager n is obtained from Y). First, in the display coordinate system, the relationship between P and PA is obtained by following the equation (1) of the chromatic aberration correction process.

[Equation 1] Next, the display coordinate system and the imager coordinate system are calculated.
(Xn, yn) represents the amount of parallel movement of the origin of each coordinate system, and θn represents the inclination of each coordinate system. At this time, both coordinate systems can be converted according to the equation (2).

[Equation 2]

From equations (1) and (2), x'and ky '
Is expressed by the equation (3).

[Equation 3] Here, k is, for example, in an NTSC imager (imaging device) configured by horizontal 768 pixels and vertical 480 pixels,
As shown in FIG. 7, the pixel pitch differs between the vertical and horizontal directions, and the vertical pitch is longer than the horizontal pitch. The coefficient is used to match the actual space aspect ratio with the memory space aspect ratio. It is the aspect ratio of the real space and k = 2.4.

Based on the above principle, the display position (X, Y)
From this, the addresses x _A and ky _A to be accessed on the memory can be obtained according to the equation (4).

[Equation 4] In the equation (4), S = C + Df, f is the focal length of the lens, and C and D are constants determined by the lens as described above. Xn, Yn and θn are determined by the mounting accuracy of the imager.

According to the above-described embodiment, when the pixel data of the black circle is obtained in FIG. 7, in addition to the white circle (AB), the pixel data (C which is the closer pixel data, C
Since the correction can be performed by using D), higher quality correction can be performed. Further, the generation of the above correction address is expressed by a linear expression as described above, and the change in the constant in the expression is a constant determined by the mounting of the imager and the lens state, so the circuit scale for realizing the operation of the expression is It can be small.

Next, the optical low-pass filters 1A to 1D in the embodiment of the present invention will be described with reference to FIGS. The optical low-pass filters 1A to 1D here are
The present invention relates to an optical low-pass filter for preventing the occurrence of false colors and a decrease in color resolution of a conventional single-plate color imager. Since the CCD used as an imager samples spatial information discretely, the original information cannot be reproduced unless the sampling frequency and the fineness of the input information satisfy the sampling theorem. In particular, when the complementary color checkered filter as shown in FIG. 3 is used, the output signal changes every two pixel cycles, and the input signal is modulated, so that a false signal other than the original signal is generated. Will end up.

When a color carrier of frequency fc is modulated with a signal of a certain spatial frequency f, as shown in FIG. 8 (A), f
A signal having frequency components of c, fc + f, fc-f, and f is generated. Here, fc indicates a sampling frequency. When fc / 2 <f <fc, f falls between fc / 2 and 3fc / 2, which causes a false color. However, since the component of f is the information representing the fine component of the image, conventionally, the cutoff frequencies of the optical low-pass filters (LPF) 1A to 1D of FIG. 1 are optimized so that the false color and the resolution of the final image are within acceptable levels. Was there.

FIG. 8B shows the spectrum of the color carrier and the sampling frequency when the conventional optical LPF is used. In the figure, the solid line part shows the luminance signal component, and the shaded part shows the modulation component by the color carrier. As is clear from the figure, the trap frequency is set to a substantially color carrier frequency, and the false color signal is generated.

Therefore, in the present embodiment, the cutoff frequency shown in FIG. 1C is set to a frequency lower than that of the conventional one (fc in this example).
/ 2), and the occurrence of the false color signal is suppressed by avoiding the overlapping of the modulation component and the luminance signal component due to the color carrier. That is, in FIG. 8A, when 0 <f <fc / 2, fc and fc ± f fall between fc / 2 and 3fc / 2, and the occurrence of false color is suppressed.

On the other hand, considering the resolution, conventionally, the number of pixels constituting one screen is 480 × 76 as shown in FIG.
In contrast to this, in the present embodiment, as described above, two sensors are arranged in the horizontal direction and two sensors in the vertical direction as described above, so the total number of pixels is twice that of the conventional one. Become. With one sensor, only the information magazine that can be obtained with 768/2 pixels can be obtained as the information input by the optical LPF, but since two sensors are provided, the same resolution as the conventional one can be obtained.

The gist of the above embodiment can be expressed as follows. A plurality of image display screen areas each having a predetermined number of pixel arrays in the horizontal direction and the vertical direction are divided into a plurality of areas, and a plurality of partial areas arranged at predetermined positions to generate a partial image corresponding to each partial area. The cutoff frequency of the image pickup device is higher than that of the case where the image pickup device is provided corresponding to each of the plurality of image pickup devices and the image pickup device is used alone so as to obtain an output corresponding to the entire image display screen area. A camera with an optical low-pass filter that is set low.

[0027]

As described above, according to the present invention,
Since the chromatic aberration is electrically corrected, the chromatic aberration correction optical system is prevented from becoming large, and the camera can be further downsized.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a camera according to the present invention.

FIG. 2 is an image pickup process circuit 5 in the embodiment shown in FIG.
The detailed block diagram of each of A to 5D is shown.

FIG. 3 is an operation explanatory diagram of a single-plate color imager in which each complementary color filter is stretched in a checkered pattern.

FIG. 4 is a diagram showing signals YL, C1 and C2 for each line (n-1, n, n + 1 ... Line).

FIG. 5 is a diagram showing a coordinate area when a copy body (photographing) area is vertically and horizontally divided into four areas (area 1 to area 4) and each area is associated with four images.

FIG. 6 is a diagram for explaining coordinate conversion for compensating a shift in the coordinate axis direction and a rotation shift about the origin.

FIG. 7 is a diagram showing a pitch of pixels stored in a memory in the NTSC system.

FIG. 8 is a spectrum diagram of color carriers and sampling frequencies.

FIG. 9 is a diagram showing the number of pixels forming one screen.

FIG. 10 is a diagram for explaining an image pickup apparatus using a plurality of image pickup elements having a relatively small number of pixels.

11 is a diagram illustrating a configuration of the image pickup apparatus shown in FIG.

[Explanation of symbols]

 1A-1D Optical low-pass filter 2A-2D Image sensor (CCD) 3A-3D S / H & AGC part 4A-4D A / D converter 5A-5D Imaging process part 6A-6D Field memory 7A-7D Interpolation processing part 8 Changeover switch 9 Encoder 10 D / A converter 11 Timing generator 12 Memory control unit 13 Interpolation coefficient generation unit

Claims (1)

[Claims] 1. A predetermined position to cover generation of a partial image corresponding to each partial area formed by dividing a color image display screen area having a predetermined number of pixel arrays in the horizontal direction and the vertical direction. A plurality of color image pickup devices arranged on the plurality of color image pickup devices, a memory means for storing color pixel outputs arranged on the plurality of color image pickup devices so that arrangement position information of the pixels is stored, and the memory. A chromatic aberration correcting means for reading out the color pixel output stored in the means so as to correct the chromatic aberration of the optical system by calculation, and a camera.