JPH05122559A - Vertical contour correction circuit for image pickup device - Google Patents

Abstract

PURPOSE:To obtain a luminance signal emphasizing the vertical contour of an image by adding a signal component emphasizing luminance before and after 1H and a signal inverting difference D of a luminance level to the 1H delayed luminance signal having the difference D at every 1 horizontal scan period (H) and canceling the difference D. CONSTITUTION:Since an adder circuit 3 adds the luminance signal 2H delayed by 1H delay lines 1 and 2 to a source luminance signal (a), for a luminance signal (c) outputted from a first subtraction circuit 4, the original luminance signal (a) and the 2H delayed luminance signal are subtracted from a luminance signal (b) 1H delayed by the delay line 1. When the signal (c) is passed through a slice circuit 5, the difference D of the luminance level at every 1H of the (a) is ignored, and the signal (c) is turned to a luminance signal (d) emphasizing the luminance pf the edge part before and after 1H. When the signal (c) is subtracted from the signal (d) through a level adjustment amplifier 7 by a subtraction circuit 6, a luminance signal (e) inverting the differential signal D is outputted. When an adder circuit 8 adds a luminance signal (f) adding the signals (d) and (e) to the signal (b), a luminance signal (g) canceling the difference D is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical contour correction circuit for enhancing a vertical image contour in a video camera or the like using a solid-state image pickup device.

[0002]

2. Description of the Related Art A vertical contour correction circuit for a conventional video camera is shown in FIG. If the original luminance signal h in the video signal output by the solid-state imaging device has an edge portion where the luminance greatly changes in the vertical direction as shown in FIG. 4, this luminance signal h and two 1H delay lines 11, 2H after passing 12
The luminance signal j obtained by adding the delayed luminance signal i (“H” indicates the horizontal scanning period) in the first addition circuit 13 has a stepwise change in luminance as shown in the edge portion. Also,
Luminance signal k passing through the 1H delay line 11 and delayed by 1H
When the luminance signal j is subtracted from the
It is possible to obtain the luminance signal 1 in which only the luminance around 1H of the edge portion is emphasized. Then, after the low-level noise of the luminance signal 1 is clipped by the noise clipping circuit 15, when the luminance signal k delayed by 1H is added by the second addition circuit 16, the original luminance signal h (actually, the luminance signal delayed by 1H is added. The edge portion of k) is emphasized, and the luminance signal m in which the contour of the image is clear can be obtained.

[0003]

In the solid-state image pickup device of a video camera, for example, if a slight deviation occurs in the process of forming a color filter, a slight difference in luminance level occurs every 1H of the luminance signal. It may appear as a horizontal line for each scan line in the image. Moreover, such 1H
If the conventional vertical contour correction circuit emphasizes the contours of luminance signals having different luminance levels, the difference between the luminance levels for each 1H is also emphasized.

Further, when the subtraction circuit 14 subtracts the luminance signal j from the luminance signal k delayed by 1H,
Since the luminance signal j having a difference of 1H is substantially inverted and added, the luminance signal l outputted has the difference D in the luminance level emphasized. Moreover, even when the second addition circuit 16 adds the luminance signal 1 and the luminance signal k delayed by 1H, there is no delay difference between them, so that the luminance signal m to be output has the difference in luminance level. D will be further emphasized and expanded to 3 times the original size.

For this reason, in the conventional vertical contour correction circuit of a video camera, when a difference in luminance level for each 1H occurs in the luminance signal due to a slight deviation in the process of forming a color filter, not only the vertical contour is generated. However, since even a slight difference in the brightness level is emphasized, there has been a problem that the horizontal line appearing for each scanning line of the image significantly deteriorates the image quality.

In view of the above situation, the present invention provides an image pickup apparatus capable of offsetting a slight difference in luminance level for each 1H while enhancing the vertical contour of a video signal. It is an object to provide a vertical contour correction circuit.

[0007]

A vertical contour correction circuit according to the present invention comprises a first delay means for delaying an original luminance signal in a video signal outputted by an image pickup means by one horizontal scanning period, and the first delay means.
Second delay means for further delaying the output luminance signal of the delay means by one horizontal scanning period, first subtracting the original luminance signal and the output luminance signal of the second delay means from the output luminance signal of the first delay means Subtracting means, slicing means for extracting only a signal component of a predetermined level or more from the output luminance signal of the first subtracting means, second subtracting means for subtracting the output luminance signal of the first subtracting means from the output luminance signal of the slicing means, And the first
The adding means for adding the output luminance signal of the delay means, the output luminance signal of the slicing means, and the output luminance signal of the second subtracting means are provided, thereby achieving the above object.

[0008]

In the first subtraction means, the original luminance signal and the luminance signal delayed by 2H are subtracted from the luminance signal delayed by 1H from the original luminance signal. Therefore, if the original luminance signal has an edge portion where the luminance greatly changes in the vertical direction, the first subtraction means emphasizes 1H before the edge portion in the luminance signal delayed by 1H in the direction opposite to the luminance changing direction. Then, after 1H, a luminance signal emphasized in the luminance change direction can be obtained. Then, the conventional vertical contour correction circuit adds the output luminance signal of the first subtraction means to the luminance signal delayed by 1H to emphasize the luminance of the edge portion in the vertical direction to clearly show the contour of the image. It was possible to obtain a luminance signal that can be obtained.

However, in the vertical contour correction circuit of the present invention,
Further, the slicing means extracts only the signal component of a predetermined level or higher from the output luminance signal of the first subtracting means. Then, even if there is a slight difference in the luminance level for each 1H in the original luminance signal, the output luminance signal of the slicing means ignores this slight difference, and the output luminance signal of the slicing means 1
Only the signal components in which the brightness around H is emphasized are extracted. When the output luminance signal of the first subtracting unit is subtracted from the output luminance signal of the slicing unit by the second subtracting unit, the luminance of the edge portion around 1H is emphasized in the output luminance signal of the second subtracting unit. Signal components are canceled out,
Only the signal component of the slight difference in the brightness level for each 1H included in the output brightness signal of the first subtraction means is inverted and extracted.

Therefore, when the output luminance signal of the second subtraction means is added to the luminance signal delayed by 1H by the addition means, only the signal component having a slight difference in luminance level for each 1H from the luminance signal delayed by 1H is added. Can be offset.
Moreover, in this adding means, since the luminance signal in which only the luminance around 1H of the edge portion output from the slicing means is emphasized is also added, the luminance of the edge portion in the vertical direction in the original luminance signal is emphasized and the image is enhanced. You can also clearly show the outline of.

As a result, according to the vertical contour correction circuit of the present invention, although the contour of the image in the vertical direction can be emphasized, the solid-state image pickup device outputs due to a slight deviation in the process of producing the color filter. 1H for luminance signal
Even if there is a difference in the brightness level for each image, this difference can be canceled to obtain a video signal in which horizontal lines are not noticeable in the image.

[0012]

EXAMPLES The present invention will be described below with reference to examples.

FIG. 1 shows an embodiment of the present invention. The vertical contour correction circuit according to the present embodiment inputs the luminance signal a in the video signal output from the solid-state image sensor to the 1H delay line 1 and outputs the 1H delay line.
The luminance signal b output from the delay line 1 is input to another 1H delay line 2. These 1H delay lines 1 and 2 are delay circuits for delaying the luminance signal by 1H, respectively.

The luminance signal output from the 1H delay line 2 is
It is input to the first addition circuit 3 together with the original luminance signal a. The output of the first adder circuit 3 is connected to the inverting input of the first subtractor circuit 4. The output of the 1H delay line 1 is connected to the non-inverting input of the first subtraction circuit 4.

The output of the first subtraction circuit 4 is the slice circuit 5
And the inverting input of the second subtraction circuit 6. The slice circuit 5 is a circuit that removes low-level noise from the input luminance signal and extracts only a signal component of a predetermined level or higher. The output of the slice circuit 5 is connected to the non-inverting input of the second subtraction circuit 6 via the level adjusting amplifier 7. Further, the output of the slice circuit 5 and the output of the second subtraction circuit 6 are connected to the input of the second adder circuit 8. The output of the 1H delay line 1 and the second
The output of the adder circuit 8 is connected to the input of the third adder circuit 9,
The output of the third addition circuit 9 becomes the output of the vertical contour correction circuit.

FIG. 2 shows the operation of the vertical contour correction circuit having the above configuration.
It will be explained based on. However, here, it is assumed that there is a difference in the brightness level for each 1H in the brightness signal output from the solid-state image sensor due to a slight deviation in the process of creating the color filter.

In the first adding circuit 3, the original luminance signal a is
Since the 1H delay lines 1 and 2 add the luminance signals delayed by 2H, the luminance signal c output from the first subtraction circuit 4 is the original luminance signal b delayed by 1H by the 1H delay line 1. The luminance signal a and the luminance signal delayed by 2H are subtracted from each other. Therefore, when the original luminance signal a has an edge portion where the luminance greatly changes in the vertical direction as shown in the figure, the luminance signal c is emphasized in the direction opposite to the luminance change direction 1H before this edge portion, 1
The signal after H becomes a signal emphasized in the luminance conversion direction.

Further, when the luminance signal c is passed through the slice circuit 5, the slight difference D is neglected even when the original luminance signal a has a slight difference D in luminance level for each 1H. As a result, the luminance signal d is obtained in which only the signal component in which the luminance around 1H of the edge portion is emphasized is extracted. Then, when the luminance signal c is subtracted from the luminance signal d whose level is adjusted by the level adjustment amplifier 7 by the second subtraction circuit 6, the signal component in which the luminance of the edge portion around 1H is emphasized is canceled out, and the luminance signal c It is possible to output the extracted luminance signal e by inverting only the signal component of the slight difference D in luminance level for each 1H included in the above.

Therefore, when the luminance signal d output from the second subtraction circuit 6 is added to the luminance signal d output from the slice circuit 5 by the second addition circuit 8, a signal component in which the luminance around 1H of the edge portion is emphasized is obtained. A luminance signal f to which a signal component obtained by inverting the slight difference D in luminance level for each 1H is added is obtained. Then, when the brightness signal f is added to the brightness signal b delayed by 1H output from the 1H delay line 1 by the third adder circuit 9, the brightness around 1H at the edge portion of the brightness signal b is emphasized and the brightness is also increased. It is possible to obtain the luminance signal g in which the slight difference D of the luminance level of the signal b for each 1H is canceled.

As a result, according to the vertical contour correction circuit of the present embodiment, the contour of the image can be made clear by emphasizing the edge portion in the vertical direction, and a slight deviation in the process of producing the color filter. Even if there is a difference in the brightness level for each 1H in the brightness signal output by the solid-state image sensor, the difference is canceled out so that the horizontal line for each scanning line is inconspicuous, and thus the image quality of the video signal is improved. Can be prevented.

[0021]

As is apparent from the above description, according to the vertical contour correction circuit of the present invention, the luminance signal output from the solid-state image pickup device is changed in luminance level for each 1H due to a slight deviation in the process of forming the color filter. Even if a difference occurs, the difference can be canceled and a video signal in which the contour of the image in the vertical direction is emphasized can be obtained.

[Brief description of drawings]

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

FIG. 2 is a time chart of each luminance signal for showing the operation of the embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional vertical contour correction circuit.

FIG. 4 is a time chart of each luminance signal for showing the operation of the conventional example.

FIG. 5 is a time chart of each luminance signal for showing the operation of the vertical contour correction circuit when a difference in luminance level for each 1H occurs in the conventional example.

[Explanation of symbols]

 1 1H delay line 2 1H delay line 3 1st addition circuit 4 1st subtraction circuit 5 slice circuit 6 2nd subtraction circuit 8 2nd addition circuit 9 3rd addition circuit

Claims (1)

[Claims] 1. A first delay means for delaying an original luminance signal in a video signal outputted by an image pickup means by one horizontal scanning period, and a second delay means for further delaying an output luminance signal of the first delay means by one horizontal scanning period. A first subtraction means for subtracting an original brightness signal and an output brightness signal of the second delay means from an output brightness signal of the first delay means, and a signal of a predetermined level or more from the output brightness signal of the first subtraction means Slice means for extracting only the component, second subtraction means for subtracting the output brightness signal of the first subtraction means from the output brightness signal of the slice means, output brightness signal of the first delay means, and output brightness of the slice means A vertical contour correction circuit for an image pickup device, comprising: an addition means for adding a signal and an output luminance signal of the second subtraction means.