JP2001086515A - Image pickup unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To emphasize a contour of spatial frequency components of which frequencies are higher than a frequency (1/4) fsv that is 1/4 of a vertical sampling frequency fsv being a pixel rate of a CCD. SOLUTION: A delay circuit 20 of the image pickup unit receives a full line image pickup signal read from a CCD image sensor and gives signals [H1D]-[H4D] by four consecutive lines to a 2nd vertical contour emphasis circuit 50 of a Y process circuit 40 via a pre-processing circuit 30. A subtractor 51 of the 2nd vertical contour emphasis circuit 50 sums/subtracts the signals [H1D]-[H4D] outputted from each of delay elements 21-24 to obtain a signal -[H1D]+[H2D]+[H3D]-[H4D] as an output from the subtractor 51. This output is extracted through a horizontal low pas filter 52 and an amplifier 53. The contour can be emphasized around the spatial frequency components higher than the frequency (1/4) fsv through the arithmetic operation of the four lines of the signals in the vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device,
In particular, the present invention relates to an imaging device applied to a video camera using a complementary color mosaic color coding CCD.

[0002]

2. Description of the Related Art In a single-panel CCD color camera system, for example, in which a single solid-state image pickup device such as a CCD image sensor is used to pick up a color image, a CCD image sensor as an image pickup device is provided for each pixel. It is necessary to provide filters of different colors, so-called color coding filters.

FIG. 8 shows a specific example of a color arrangement structure of a complementary mosaic color coding filter as an example of such a color coding filter.
y represents cyan (blue-green), Ye represents yellow (yellow), G represents green (green), and Mg represents magenta (red-purple), and the i-th (0 ≦ i) of each line N0, N1,. X represents the color X of the j-th pixel (0 ≦ j) in the line Ni. For example, G12 is the color G of the second pixel of the line N1.
(Green). In the example of FIG. 8, the horizontal (horizontal) direction is repeated at a two-pixel cycle, for example, Cy, Ye, Cy, Ye,..., And the vertical (vertical) direction is, for example, Cy, Ye.
G, Cy, Mg,..., Are repeated in a four-pixel cycle (four-line cycle). That is, the horizontal repetition cycle is two pixels, and the vertical repetition cycle is four lines.

FIG. 9 is a block diagram showing an example of a camera signal processing system of a video camera device which is an image pickup device using the CCD image sensor 102 of such a complementary color mosaic color coding filter.

[0005] In FIG. 9, an image pickup signal obtained by image pickup by a CCD image sensor 102 as an image pickup device through an optical system 101 including a lens of a camera unit and a mechanical shutter and the like, and photoelectrically converted is converted into a CDS (correlation) signal. Double sampling) circuit, GCA (gain control amplifier),
The signal is sent to the delay circuit 120 via the front end circuit 103 including an A / D (analog / digital) converter and the like. A read pulse signal from the timing generation circuit 106 is supplied to the CCD image sensor 102, and a sampling pulse, an A / D conversion drive pulse, and the like from the timing generation circuit 106 are supplied to the front end circuit 103. A control signal from the system control circuit 107 is supplied to the timing generation circuit 106, and a delay circuit 120
Also, a control signal from the system control circuit 107 is supplied. The output signal from the delay circuit 120 is
The signal is sent to the Y (luminance) process circuit 140 and the C (chroma) process circuit 160 via 0. A control signal from the system control circuit 107 is also supplied to the Y process circuit 140 and the C process circuit 160.

In the system shown in FIG. 9, the field read of the interlaced scan CCD is performed. As shown in FIG. 10, adjacent pixel data of two lines in the vertical direction on the CCD are added, and Are read out as shown in FIG. This is also called two-line mixed reading. As described above, when two lines N0 + N1, N2 + N3,... Are mixed and added in one field and read out, N1 + N1
, + N2, N3 + N4,... Are mixed and read.

[0007]

Incidentally, one of the luminance signal processes including the Y process circuit 140 shown in FIG. 9 includes a vertical edge enhancement process, which is related to the vertical edge enhancement process. FIG. 12 shows the structure of the part.
Shown in In FIG. 12, delay circuit 120 has 2
Two 1H (one horizontal period, one line) delay elements 121, 1
22 and the 1H delay signal [HH1
D], the 2H delay signal [HH2D] is taken out, and the pre-processing circuit 13
Sent to 0. In the preprocessing circuit 130, the signal [HH0
D] and [HH2D] are added by the adder 131, and the half multiplier 13 is added.
It is sent to the Y process circuit 140 after being halved by 2. The 1H delay signal [HH1D] is directly sent to the Y process circuit 140 as a signal to be processed.

In the Y process circuit 140, the 1H delay signal [HH1D] is sent to the main line processing circuit 141 for luminance signal and the vertical contour emphasizing circuit 144. Main line processing circuit 14
In 1, processes such as H (horizontal) direction contour enhancement and γ correction are performed, and the output signal from the vertical contour enhancement circuit 144 is added by the adder 142. In the vertical contour emphasis circuit 144, the 1H delay signal is subtracted by the subtractor 145.
From [HH1D], ([HH0D] + [H
H2D]) / 2 is subtracted and the horizontal low-pass filter 14
6, via the amplifier 147, and sent to the adder 142 of the main line processing circuit 141.

In such vertical edge enhancement, the vertical edge enhancement signal [VAPC] output from the vertical edge enhancement circuit 144 is [VAPC] = [HH1D]-([HH0D] + [HH2D]). / 2 (1) Here, since the signal from the CCD image sensor 102 is a signal obtained by adding two lines as described above, if the above equation (1) is expressed in units of the pixel rate on the CCD image sensor 102, FIG. When targeting the lines N0 to N5 in FIG. 11, [VAPC] =-0.25 * [N0] -0.25 * [N1] + 0.5 * [N2] + 0.5 * [N3] -0.25 * [N4] -0.25 * [N5] (2) This corresponds to a tap coefficient of the contour emphasis filter operation of (−1, −1, 2, 2, −1, −1) (3), and the vertical sampling frequency fsv
This means that the outline is emphasized centering on the spatial frequency component lower than 1/4.

Therefore, in the conventional camera signal processing system based on the field readout method, the center frequency of the edge enhancement is の of the frequency fsv corresponding to the CCD pixel rate in the vertical direction, that is, the spatial frequency lower than (1/4) fsv. Therefore, the sharpness is reduced by that amount.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an image pickup apparatus capable of enhancing a spatial frequency component higher than (1/4) fsv by vertical contour enhancement. And

[0012]

In order to solve the above problems, the present invention provides an image pickup device having a color coding filter and a pixel rate in a vertical direction based on an output from each line of the image pickup device. 1 of the corresponding frequency fsv
Vertical edge enhancement means having a function of enhancing the edge of a spatial frequency component higher than / 4.

Here, the color coding filter may be a complementary color mosaic color coding filter. As the complementary color mosaic color coding filter, the first Cy and Ye are alternately repeated.
, A second line in which G and Mg are alternately repeated, a third line in which Cy and Ye are alternately repeated, and M
The filter may be a horizontal 2 pixel × 4 vertical line composed of a fourth line in which g and G are alternately repeated.

The vertical contour enhancing means includes a first vertical contour enhancing circuit for enhancing a vertical contour based on a signal obtained by adding two lines adjacent to each other in the vertical direction of the image pickup device; A second vertical contour emphasizing circuit for emphasizing a contour centering on a spatial frequency component higher than (1/4) fsv by calculating four lines in the vertical direction of the element.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an imaging apparatus according to the present invention will be described below with reference to the drawings. FIG.
FIG. 1 is a block diagram illustrating an example of a system configuration of a video camera device as an embodiment of an imaging device according to the present invention. FIG. 2 is a block diagram extracting and showing a configuration of a part related to vertical edge enhancement which is a main part of the present embodiment.

Referring to FIG. 1, an optical system 11 of the camera unit includes:
This optical system 1 is composed of a lens, a mechanical shutter, etc.
The optical image passing through 1 is picked up by a CCD image sensor 12, which is an image pickup device, and photoelectrically converted. This CCD
The image sensor 12 is capable of reading all pixels, and specifically reads all pixels by reading frames of an interlaced scan CCD. This interlaced scan and frame readout 2
The signal of the field is an image exposed at the same time by the mechanical shutter of the optical system 11.

An image pickup signal obtained from the CCD image sensor 12 is supplied to a front end circuit 13. This front-end circuit 13 is a CDS (correlation 2) for detecting charges of each pixel photoelectrically converted and accumulated by the CCD.
Double sampling) circuit, GCA (gain control amplifier), A
/ D (analog / digital) converter, etc., and the output signal from the front end circuit 13 is
The signal is sent to the delay circuit 20 via the memory control circuit 14.
The memory 15 is connected to the memory control circuit 14.
The memory 15 is for rearranging the signals read out from the frame from the CCD image sensor 12 into spatial array data on the CCD.

A read pulse signal from the timing generation circuit 16 is supplied to the CCD image sensor 12, and a sampling pulse, an A / D conversion drive pulse, and the like from the timing generation circuit 16 are supplied to the front end circuit 13. . A control signal from the system control circuit 17 is supplied to the timing generation circuit 16, and a control signal from the system control circuit 17 is also supplied to the delay circuit 120.

Here, the frame reading operation from the CCD image sensor 12 and the rearrangement operation in the memory 15 will be described with reference to FIGS. FIG. 3 is a diagram showing an image of frame readout on the CCD image sensor 12, in which all the lines N
All the individual pixels of 0, N1,... Are read out,
By interlaced scanning every other line,
The CCD output signal is, as shown in FIG.
Are divided into a first field F1 of 0, N2,... And a second field F2 of odd lines N1, N3,. . The memory control circuit 14 writes / writes the signals of these two fields F1 and F2 to the memory 15 /
By performing the read control, the data is rearranged and output in the spatial arrangement order on the CCD as shown in FIG. That is, the output signal (FIG. 5) from the memory control circuit 14 is a frame image signal according to the line order (N0, N1,...) On the CCD.

Returning to FIG. 1, the output signal from the delay circuit 20 is sent to the Y (luminance) process circuit 40 and the C (chroma) process circuit 60 via the preprocessing circuit 30. A control signal from the system control circuit 17 is also supplied to the Y process circuit 40 and the C process circuit 60.

FIG. 2 shows a configuration of a portion related to vertical edge enhancement which is a main portion of the present embodiment. 2, in a delay circuit 20, five 1H (one horizontal period, one line) delay elements 21
~ 25, signal without delay [H0D] and 1H delay signal
[H1D] to 5H delay signal [H5D] are extracted and sent to the preprocessing circuit 30. In the preprocessing circuit 30, the signal [H
The signals [H0D] and [H1D] are added by an adder 31 for the signals [0D] to [H5D], and the signals [H2D] and [H3D] are added by an adder 32.
[H4D] and [H5D] are added by an adder 33, and the output from the adder 31 and the output from the adder 33 are added by an adder 34 to be halved by a 乗 算 multiplier 35. The output signal ([H0D] + [H1D] + [H4D] + [H5D]) / 2 from the multiplier 35 and the output signal ([H2D] + [H3D]) from the adder 32 are combined into a Y process circuit. Sent to 40. The output signal from the adder 32
([H2D] + [H3D]) is the current processing target signal.

In the Y process circuit 40, the adder 32
([H2D] + [H3D]) are sent to the luminance signal main line processing circuit 41 and the first vertical contour emphasizing circuit 44, and the output signal ([[ H0D] + [H1D] + [H4
D] + [H5D]) / 2 is sent to the first vertical contour emphasizing circuit 44. The 1H delay signal [H1D] to 4H delay signal [H4D] from each of the delay elements 21 to 24 are sent to a second vertical contour emphasis circuit 50.
And the output from the first vertical contour emphasizing circuit 44 are added by the adder 54 and sent to the main line processing circuit 41. In the main line processing circuit 41, processing such as H (horizontal) contour enhancement and γ correction is performed, and the output signal from the adder 54 is added by the adder 42.

In the first vertical contour emphasizing circuit 44, the output signal ([H2D] + [H3D]) of the adder 32 is output by the subtractor 45.
From the output signal ([H0D] + [H1D] +
[H4D] + [H5D]) / 2 is subtracted, and the horizontal low-pass filter 4
6 and via an amplifier 47,
Sent to The first vertical contour emphasizing circuit 44 is the same as the vertical contour emphasizing circuit 144 in FIG.

In the second vertical contour emphasizing circuit 50, the signal [H1 from the delay elements 21 to 24 is output by the subtractor 51.
D] to [H4D] are added and subtracted,-[H1D] + [H2D] + [H3D]-
[H4D] is obtained, and the output from the subtracter 51 is taken out via the amplifier 53 via the horizontal low-pass filter 52 and sent to the adder 54. That is, the subtracter 51 of the second vertical contour emphasizing circuit 50 outputs a tap coefficient
This corresponds to a filter that performs the filter operation of (-1, 1, 1, -1). By this filter operation, -1 * [H1D] + 1 * [H2D] + 1 * [H3D] -1 * [H4D] Performs vertical edge enhancement. The signal from the subtractor 51 is １ ／ of the horizontal sampling frequency fsh due to the sensitivity difference of the complementary color mosaic color coding.
, The horizontal low-pass filter 5
2 removes the modulation component of the frequency (1/2) fsh,
After the level is adjusted by the amplifier 53, the signal is sent to the adder 54.

In the vertical contour emphasizing circuit having such a configuration, the vertical contour emphasizing signal output from the first vertical contour emphasizing circuit 44 corresponds to the above-described conventional vertical contour emphasizing signal [VAPC]. The frequency characteristics are as shown in FIG. The center frequency of the outline emphasis frequency characteristic in FIG. 6 is a spatial frequency lower than 1/4 of the sampling frequency fsv of the CCD vertical pixel rate. On the other hand, the frequency characteristic of the vertical edge enhancement signal [nVAPC] output from the second vertical edge enhancement circuit 50 is shown in FIG.
become that way. The center frequency of the outline emphasis frequency characteristics in FIG. 7 is a spatial frequency higher than １ ／ of the sampling frequency fsv of the CCD vertical pixel rate.

Therefore, in the conventional vertical contour enhancement, C
In contrast to the vertical sampling frequency fsv of the CD pixel rate, which only emphasizes the contour around the spatial frequency of (1/4) fsv or less, according to the embodiment of the present invention, (1)
/ 4) It is possible to enhance the outline of a high-frequency spatial frequency band exceeding fsv, and it is possible to create a detailed image in the vertical direction.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, an example in which the present invention is applied to a video camera apparatus has been described. In the above embodiment, the signal processing of the frame readout method using the interlaced scan CCD has been described. However, a system capable of reading data independently of each line of the complementary color mosaic color coding CCD is also described. Applicable. Further, the pixel arrangement of the complementary color mosaic color coding is not limited to the above embodiment, and may be another arrangement.
The present invention is also applicable to a case where color coding filters of three primary colors are used. In addition, it goes without saying that various changes can be made without departing from the spirit of the present invention.

[0028]

According to the image pickup apparatus of the present invention, based on the image pickup device having the color coding filter and the output from each line of the image pickup device, 1/1 / fsv of the frequency fsv corresponding to the pixel rate in the vertical direction is obtained. The provision of the vertical edge enhancement means having the function of enhancing the edge of the spatial frequency component higher than 4 enables the edge enhancement of the high frequency spatial frequency component.

Also, a first line in which Cy and Ye are alternately repeated as the color coding filter,
A second line in which G and Mg are alternately repeated, and Cy and Ye
By using a complementary mosaic color coding filter having a horizontal 2 pixel × vertical 4 line unit consisting of a third line in which is alternately repeated and a fourth line in which Mg and G are alternately repeated, as a unit. For the vertical sampling frequency fsv of the pixel rate of
4) The outline of the spatial frequency components higher than fsv can be emphasized, and a high-quality output image with high definition can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a video camera device to which an embodiment of the present invention is applied.

FIG. 2 is a block diagram extracting and showing a configuration of a portion related to vertical contour enhancement which is a main part of the embodiment of the present invention.

FIG. 3 is a diagram showing an image of frame reading on a CCD image sensor.

FIG. 4 is a diagram showing a CCD output signal when all pixels are read out by two field signals by interlaced scanning of a CCD image sensor.

5 is a diagram showing signals after rearranging the CCD output signals of FIG. 4 according to the pixel arrangement on the CCD image sensor.

FIG. 6 is a diagram showing frequency characteristics of conventional vertical contour enhancement.

FIG. 7 is a diagram illustrating a frequency characteristic of vertical contour enhancement according to a main part of the embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of a complementary color mosaic color coding filter on a CCD image sensor.

FIG. 9 is a block diagram showing an example of a camera signal processing system of a conventional video camera device.

FIG. 10 is a diagram for explaining two-line mixed reading of the CCD image sensor.

FIG. 11 is a diagram showing a CCD output signal obtained by two-line mixed reading of the CCD image sensor.

FIG. 12 is a block diagram showing a configuration of a portion related to a conventional vertical contour enhancement.

[Explanation of symbols]

12 CCD image sensor, 13 front end circuit, 14 memory control circuit, 15 memory, 2
0 delay circuit, 21 to 25 1H delay element, 30 preprocessing circuit, 31 to 34 adder, 40 Y process circuit, 41 main line processing circuit, 42, 54 adder,
44 first vertical contour emphasis circuit, 45, 51 subtractor, 46, 52 horizontal LPF, 50 second vertical contour emphasis circuit

Claims (5)

[Claims] 1. An image pickup device having a color coding filter, and a spatial frequency component higher than 1/4 of a frequency fsv corresponding to a pixel rate in a vertical direction is contour-enhanced based on an output from each line of the image pickup device. An imaging apparatus comprising: a vertical contour emphasis unit having a function. 2. The imaging apparatus according to claim 1, wherein the color coding filter is a complementary color mosaic color coding filter. 3. The complementary mosaic color coding filter comprises a first line in which Cy (cyan) and Ye (yellow) are alternately repeated, and a second line in which G (green) and Mg (magenta) are alternately repeated. A filter having a horizontal 2 pixel × vertical 4 line composed of a line, a third line in which Cy and Ye are alternately repeated, and a fourth line in which Mg and G are alternately repeated is a unit of repetition. The imaging device according to claim 2, wherein: 4. A vertical contour enhancement circuit for enhancing a contour in a vertical direction based on a signal obtained by adding two lines adjacent to each other in a vertical direction of an image pickup device, wherein the vertical contour enhancement means includes: By calculation of 4 lines in the vertical direction of the element
2. The image pickup apparatus according to claim 1, further comprising a second vertical edge enhancement circuit for enhancing an edge around a spatial frequency component higher than (1/4) fsv. 5. The image pickup apparatus according to claim 1, wherein the image pickup element scans an odd line and an even line individually and reads out the frame.