JPS63314076A - Outline compensating circuit - Google Patents

Abstract

PURPOSE:To prevent excessive outline compensation of a video signal obtained from a solid-state image pickup element by subjecting at least the black level of vertical outline component to compression processing. CONSTITUTION:A horizontal outline signal (APh) obtained by a horizontal outline signal forming circuit 10 is supplied to a signal adding circuit 16 as it is. A vertical outline signal (APv) obtained by a vertical outline signal forming circuit 11 is supplied to a clip circuit 14 from a buffer circuit 12 through a DC cutting-off capacitor 13 and is supplied to the signal adding circuit 16 through this clip circuit 14. An outline compensating signal (AP) formed by adding the horizontal outline signal (APh) and a vertical outline signal (APv') subjected to black level compression processing is used to perform outline compensation. Thus, the extent of outline compensation in the vertical direction is suppressed even in a high-luminance image part, where the outline may be excessively prominent by excessive outline compensation, to perform natural outline compensation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention performs contour compensation processing by extracting horizontal contour components and vertical contour components from a video signal obtained from a solid-state image sensor and adding them to the video signal. The present invention relates to a contour compensation circuit for a solid-state imaging device.

C. Summary of the Invention The present invention provides a contour compensation circuit for a solid-state imaging device that performs contour compensation processing by extracting horizontal contour components and vertical contour components from a video signal obtained from a solid-state imaging device and adding them to the video signal. By performing compression processing on at least the black level of the vertical contour component, excessive contour compensation for the video signal obtained from the solid-state imaging device is prevented.

[Conventional technology]

In general, video equipment such as video cameras and video tape recorders use transversal filters, bandpass filters, etc. to convert video signals into Contour compensation processing is performed in which horizontal contour components and vertical contour components are extracted and added to the video signal.

For example, in a video camera that uses an image pickup tube such as a vidicon as an imaging unit to form a video signal of a subject, the beam current is changed according to the brightness of the subject image, so that more beam current is applied to high-brightness images. Because of this, when photographing a high-brightness subject, the scanning beam diameter becomes thick, causing resolution degradation, and there is also so-called beam bending, which causes the image to bulge, reducing the sharpness of the outline of the high-brightness image. Since this is low, contour compensation processing is performed by extracting horizontal contour components and vertical contour components from the video signal formed by the imaging section and adding them to the video signal.

In addition, charge coupled devices (CCDs) have traditionally been used instead of image tubes such as vidicon.
A solid-state imaging device using a solid-state imaging device such as ICE) in an imaging section has been put into practical use.

[Problem that the invention seeks to solve]

By the way, in a solid-state imaging device having a discrete pixel structure such as a CCD, which is used as an imaging section of a solid-state imaging device,
A high resolution determined by the pixel structure can be obtained without causing resolution deterioration or beam bending caused by the above-mentioned storage.

Therefore, in a solid-state imaging device that uses a solid-state imaging device as an imaging section, contour compensation is performed in which horizontal contour components and vertical contour components are extracted from a video signal using a transversal filter, a bandpass filter, etc., and added directly to the video signal. If this processing is performed, there is a risk that excessive contour compensation will be performed. In particular, as shown in FIG. 4, the oblique contour line 42 that appears in a step-like manner in a high-brightness image 41 reproduced with a video signal subjected to contour compensation processing is emphasized, resulting in an unnatural image 40.
Become.

In view of the conventional problems as described above, the present invention provides a solid-state image sensor that performs contour compensation processing by extracting a horizontal contour component and a vertical contour component from a video signal obtained from a solid-state image sensor and adding them to the video signal. In the contour compensation circuit of the imaging device, excessive contour compensation for the video signal obtained from the solid-state image sensor is prevented by performing compression processing on the vertical contour components (both black level) and high-brightness images. An object of the present invention is to provide a contour compensation circuit for a solid-state imaging device having a novel configuration that can perform natural contour compensation even for objects.

[Means for solving problems]

In order to solve the conventional problems as described above, the present invention has the following features:
In the contour compensation circuit that extracts a horizontal contour component and a vertical contour component from a video signal obtained from a solid-state image sensor and adds them to the video signal, a black compression circuit is provided that compresses at least the black level of the vertical contour component. It is characterized by

[Effect]

The contour compensation circuit according to the present invention performs contour compensation in the vertical direction by adding at least a vertical contour component with a compressed black level to a video signal obtained from a solid-state image sensor.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

The first embodiment shown in the block diagram in FIG. Concerning the obtained video signal (Sin) of a subject image (not shown), the contour compensation circuit 3 according to the present invention
The contour compensation process is performed on the video signal (
Sout) is output from the signal output terminal 4.

The contour compensation circuit 3 receives the video signal (Sin) from the CCD image sensor l via the video signal processing unit 2.
) is provided with a horizontal contour signal forming circuit 10 and a vertical contour signal forming circuit 11 to which a signal is supplied.

The horizontal contour signal forming circuit 10 includes the video signal (Si
A horizontal contour component is extracted from n) to form a horizontal contour signal (APh). The horizontal contour signal forming circuit 10
The horizontal contour signal (APh) obtained in
The signal is supplied to the signal addition circuit 16 of.

Further, the vertical contour signal forming circuit 11 extracts a vertical contour component from the video signal (Sin) to form a vertical contour signal (APv). The vertical contour signal (APv) obtained by the vertical contour signal forming circuit 11 is supplied from the buffer circuit 12 to the clip circuit 14 via the DC cutoff capacitor 13, and via the crimp circuit 14 to the first The signal is supplied to the signal addition circuit 16.

The clip circuit 14 has an output terminal connected to the base of the buffer circuit 12 via the capacitor 13.
PN) transistor 14A and NPN with clip power supply 15 connected to the base) transistor 14B and the above NPN
PN) transistor 14A.

and a load resistor 14C to which each emitter of the NPN transistor 14A is commonly connected.

14B are commonly connected to a positive power supply terminal, and each emitter is connected to a negative power supply input terminal via a common load resistor 14C. This clip circuit 14 consists of the above-mentioned NPN) transistors 14A and 14B.
is a non-additive mixer (NAM:N).

For example, the capacitor 13 operates as a second adder mixer, and the DC component is removed by the capacitor 13, rather than the negative clip voltage (Ect) applied to the base of the NPN transistor 14B by the clip power supply 15.
As shown in (A) of the figure, when the vertical contour signal (APv) decreases, the decreased portion is applied to the clip voltage (-ECL).
2, the negative side of the vertical contour signal (APv), that is, the black level, is clipped by the clip voltage (Ect) and black level compression processing is performed, as shown in FIG. 2 (B). (APv') is formed. and,
The vertical contour signal '(APv') which has been subjected to black level compression processing and obtained by the clip circuit 14 is supplied to the first signal addition circuit 16 .

The first signal addition circuit 16 receives the horizontal contour signal (APh) directly supplied from the horizontal contour signal forming circuit IO.
) and the black level compressed vertical contour signal (APv") supplied from the vertical contour signal forming circuit 11 via the clipping circuit 14, thereby forming an contour compensation signal (AP). .

The contour compensation signal (AP) obtained by the first signal addition circuit 16 is sent to the second crispening circuit 17, which suppresses the contour component due to noise by clamping the small signal level region to 0 level. The signal is supplied to the signal addition circuit 18.

The second signal addition circuit 18 includes the video signal processing section 3
A video signal (Sin) is supplied from the video signal (Sin), the contour compensation signal (AP) is added to this video signal (Sin) to perform contour compensation, and the contour compensation processed video signal (Sout) is obtained.
is output from the signal output terminal 4.

As in the first embodiment, the video signal (Sin) obtained by the CCD image sensor 1 is divided into a horizontal contour signal (APh) and a vertical contour signal (APh) that has been subjected to black level compression processing.
By performing contour compensation using the contour compensation signal (8P) formed by adding APv'), it is possible to perform contour compensation even for high-brightness image parts where the contour line may be too conspicuous due to excessive contour compensation. , natural contour compensation can be performed by suppressing the amount of contour compensation in the vertical direction.

Next, the second embodiment shown in the block diagram of FIG.
The present invention is applied to a solid-state imaging device equipped with a D-image sensor 21, and the contour according to the present invention is applied to a video signal (Sin) of a subject image (not shown) obtained from the image sensor 21 via the video signal processing unit 22. Compensation circuit 2
In step 3, contour compensation processing is performed, and the contour-compensated video signal (Sout) is output from the signal output terminal 24.

The contour compensation circuit 23 includes the CCD image sensor 2
A horizontal contour signal (APh) is formed by the horizontal contour signal forming circuit 31 from the video signal (Sin) supplied from 1 through the video signal processing section 22, and a horizontal contour signal (APh) is formed by the vertical contour signal forming circuit 32. The vertical contour signal (APv) is the first
A crispening circuit in which a contour compensation signal (AP) is obtained by addition and synthesis in a signal addition circuit 33, and this contour compensation signal (8P) is supplied from a buffer circuit 34 via a DC cutoff capacitor 35. In step 36, crispening processing is performed and black level compression processing is performed on the vertical contour component, resulting in a contour compensation signal (^P) that has undergone black level compression processing.
) is supplied to the second signal addition circuit 37, and the contour compensation signal (AP') is added to the video signal (Sin) to perform contour compensation.

In the above Crispinning circuits 3 and 6, the anode is a resistor 40.
A first diode 41 is connected to a positive voltage input terminal via a resistor 42, and a second diode 43 whose cathode is connected to a negative voltage input terminal via a resistor 42 is provided. The first diode 41 has its cathode connected to the input end 36A through a parallel circuit of a resistor 44 and a capacitor 45, and its anode connected to the output end 36B through a resistor 46.
It is connected to the. The second diode 43 has its anode connected to the input terminal 36A and grounded via a resistor 47, and its cathode connected to the output 636B via a resistor 47. Further, the anode of the first diode 41 is connected to the cathode of the second diode 43 via a semi-fixed resistor 49.

The crisp pinning circuit 36 passes a contour compensation signal (8P) of a signal level that can turn on the first diode 41 and the second diode 43, and A crispening operation is performed in which the contour compensation signal (AP) at a minute signal level that cannot turn on the signal 43 is regarded as noise and is clamped to the O level. The range of the minute signal level is set by the anode bias of the first diode 41 and the cathode bias of the second diode 43, which are adjustable by the semi-fixed resistor 49. In this embodiment, the impedance of a parallel circuit of a resistor 44 and a capacitor 45 arranged on the cathode side of the first diode 41 of the crispening circuit 36 is turned on by the black level of the contour compensation signal (AP). , the compression ratio of the black level of the contour compensation signal (AP) is determined by the ratio of the output impedances on the anode side of the first diode 41. The impedance of the parallel circuit of the resistor 44 and capacitor 45 has a frequency characteristic such that black level compression is not performed on high frequency horizontal contour components, but black level compression is performed only on low frequency vertical contour components. is set to a value with .

In this second embodiment, regarding the video signal (Sin) obtained by the CCD image sensor 21, the horizontal contour signal (
APh) and a vertical contour signal (APh) subjected to black level compression processing
The contour compensation signal (A
P) In the crispinning circuit 36, a black level crispening processing system performs level compression processing that gives frequency characteristics to form a contour compensation signal (AP") in which only the vertical contour component is level-compressed. By performing contour compensation using the contour compensation signal (AP'), the amount of contour compensation in the vertical direction is suppressed for high-brightness image areas where the contour lines may become too conspicuous due to excessive contour compensation. Contour compensation can be performed.

〔Effect of the invention〕

The contour compensation circuit of the solid-state imaging device according to the present invention performs vertical contour compensation by adding at least a vertical contour component obtained by compressing the black level to the video signal obtained from the solid-state image sensor, so that a step-like appearance appears. Diagonal contour lines are not emphasized more than necessary, and natural contour compensation can be performed even on high-brightness images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the above embodiment, and FIG. 3 is a block diagram showing a second embodiment of the present invention. FIG. FIG. 4 is a schematic diagram showing the state of an image reproduced when conventional contour compensation processing is applied to a video signal obtained from a solid-state image sensor. 1.21... CCD image sensor 3.23... Contour compensation circuit 10.31... Horizontal contour signal forming circuit 11.32...
・Vertical contour signal forming circuit 14...Clip circuit

Claims (1)

[Claims] In a contour compensation circuit that extracts a horizontal contour component and a vertical contour component from a video signal obtained from a solid-state image sensor and adds them to the video signal, compression processing is performed on at least the black level of the vertical contour component. A contour compensation circuit for a solid-state imaging device, comprising a black compression circuit.