JPH08102888A - Image pickup device - Google Patents

Abstract

PURPOSE: To improve characteristic of a contour correction circuit at the time of executing a signal processing such as gamma correction in an analog signal form by generating a delay signal by converting a video signal to a digital signal and generating the contour correction signal of the analog signal form from this delay signal. CONSTITUTION: A signal processing circuit 5 executes signal-processing such as gamma correction, knee processing in the analog signal form with respect to an output signal and after then, adds the signal-processed output signal with the contour correction signal generated by a contour correction signal generation circuit 8 to emphasize the contour of a video. The contour correction signal generation circuit 8 converts the signal-processed output signal to the digital signal to generate first and second delay signals obtained by delaying this output signal respectively by one or two horizontal scanning period. The contour correction signal is generated by adding and subtracting these first and second delay signals and the output signal, and the second delay signal is generated by delaying the first delay signal by one horizontal period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device and can be applied to, for example, a television camera.

[0002]

2. Description of the Related Art Conventionally, in a television camera,
By emphasizing the contour of the video signal with the contour correction circuit,
The resolution of the video signal is visually improved.

That is, the contour correction circuit generates a contour correction signal from a video signal and adds the contour correction signal to the video signal to emphasize the contour of the video signal. Here, the contour correction signal is
It is generated by adding two types of contour correction signals, each of which emphasizes the contour.

Of these, the contour correction signal in the vertical direction is first delayed by one horizontal scanning period of the video signal, whereby one horizontal scanning period and two horizontal scanning periods from the original video signal.
First and second delay signals delayed by the horizontal scanning period are generated. The contour correction circuit defines the first delay signal as a video signal of the main line, and subtracts the original video signal from the video signal of the main line to generate a first contour correction component. Further, the contour correction circuit subtracts the second delay signal from the video signal of the main line to generate a second contour correction component, and adds the first and second contour correction components to obtain a vertical direction. The contour correction signal of is generated.

Therefore, this vertical contour correction signal is obtained by observing a change in the signal level in the vertical direction of the display image.
It is formed so that the signal level rises after the signal level falls at the timing when the video signal level of the main line rises. On the contrary, when the video signal level of the main line falls, the signal level rises after the fall timing, and then the signal level falls.

As a result, the contour correction signal can be added to the video signal of the main line to emphasize the rising and falling of the signal level of the video signal in the vertical direction. Note that the contour correction circuit similarly delays the video signal in the horizontal direction to generate a contour correction signal.

[0007]

In a television camera of this type, a signal processing circuit such as a gamma correction circuit including a contour correction circuit and a shading correction circuit is formed of an analog circuit and a digital circuit. There is something I did. Among them, the television camera in which the signal processing circuit is formed by an analog circuit consumes less power than the one formed by a digital circuit and has a characteristic that the entire structure can be simplified. However, in a television camera in which the signal processing circuit is formed by an analog circuit, there is a problem that the characteristics of the contour correction circuit are still insufficient in practical use.

That is, in a television camera in which the signal processing circuit is formed by an analog circuit, so-called glass delay lines are used to generate the above-mentioned first and second vertical delay signals. Here, this glass delay line is formed by forming electrodes for input and output on a glass plate having a predetermined shape. The input electrodes are driven by a video signal to form mechanical vibrations. Is taken out from the output electrode, the video signal is delayed by utilizing the time required for the mechanical vibration to propagate through the glass plate.

Therefore, the glass delay line cannot avoid variations in delay time due to variations in the glass plate, and further has a drawback that the delay time changes with temperature. Further, the glass delay line has drawbacks that it changes over time, its insertion loss is large, and its frequency characteristics are insufficient. Further, there is a drawback that unnecessary reflection occurs, and it is difficult for a television camera to reduce this unnecessary reflection.

Of these, the delay time varies, the temperature changes,
After the change over time, it becomes difficult to enhance the contours at the correct timing with respect to the primary color signals of red, blue, and green that enhance the contours, and the registration of the display image deteriorates. Therefore, a television camera requires a correction circuit for correcting temperature changes and the like. Moreover, since the insertion loss is large, the SN of the delay signal is
There is also a drawback that the deterioration of the ratio cannot be avoided and the image quality of the displayed image deteriorates accordingly. Also, a correction circuit for correcting the frequency characteristic is required, and in this case, the group delay characteristic of the video signal also deteriorates,
If the degree of modulation further decreases, the resolution will deteriorate.

The present invention has been made in consideration of the above points, and proposes an image pickup apparatus capable of improving the characteristics of a contour correction circuit in an image pickup apparatus which executes signal processing such as gamma correction in an analog signal format. Is what you are trying to do.

[0012]

In order to solve the above problems, the present invention provides an image pickup apparatus for converting an output signal of a solid-state image pickup device into a video signal after outputting a signal from the signal processing circuit. The processing circuit performs signal processing on the output signal in the form of an analog signal, adds the contour correction signal generated by the contour correction signal generation circuit to emphasize the contour of the video signal, and the contour correction signal generation circuit performs signal processing. The output signal is converted into a digital signal, and the output signal is delayed by one horizontal scanning period and two horizontal scanning periods to generate first and second delay signals, and the first delay signal and the second delay signal are generated. The delay signal and the output signal are added / subtracted to generate a contour correction signal, and the first delay signal is delayed by one horizontal scanning period to generate a second delay signal.

[0013]

When the contour correction signal generated by the contour correction signal generation circuit is added to emphasize the contour of the video signal after the signal processing of the output signal in the form of an analog signal, the contour correction signal generation circuit outputs the output signal. To convert the digital signal into a digital signal to generate the first and second delay signals, effectively avoid the deterioration of the frequency characteristic, and hold the delay time with high accuracy in one horizontal scanning period and two horizontal scanning periods. You can

[0014]

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 2, reference numeral 1 denotes a television camera as a whole, which picks up an image of a desired subject through an optical system including a zoom lens 2 and outputs a video signal SV.

That is, in the television camera 1, in the dichroic prism 3, the incident light from the zoom lens 2 is separated into red, green, and blue light rays, and the respective light rays are received by the solid-state image pickup devices 4R, 4G, and 4B. As a result, the television camera 1 has the solid-state image pickup devices 4R and 4R,
Red, green, and blue color signals R output from G and 4B,
After G and B are processed by the subsequent signal processing circuit 5, the encoder 6 converts them into a video signal SV.

Here, the signal processing circuit 5 inputs the red, green and blue color signals R, G and B through an amplifier circuit (not shown), and performs shading correction and gamma on the color signals R, G and B. Signal processing such as correction and knee processing is executed. At this time, the signal processing circuit 5 emphasizes the contours of the respective color signals R, G, and B in the contour correction circuit 7, thereby improving the resolution of the video signal SV.

For this reason, the contour correction circuit 7 generates the contour correction signal DTL by the built-in contour correction signal generation circuit 8 and the color signals R and 9 are added to the addition circuits 9R, 9G and 9B, respectively.
The contour correction signal DTL is added to G and B. As a result, the contour correction circuit 7 causes the red, green, and blue color signals R, G, B
Emphasize the outline of each. In this example,
For the green color signal G, the contour correction circuit 7 replaces the green color signal G with a green delayed color signal G1 delayed by one horizontal scanning period with respect to the green color signal G, and outputs the contour correction signal DTL. Are added, and thereby the timing correction of the green color signal G is made to coincide with the contour correction signal DTL.

Here, as shown in FIG. 3, the contour correction signal generation circuit 8 generates a contour correction signal DTL from the green color signal G. That is, the contour correction signal generation circuit 8 supplies the green color signal G to the clamp circuit 10 and clamps it by the clamp pulse CLP. Mixer (MIX) 11
Inputs the green color signal G and the sample pulse VS output from the clamp circuit 10, and inserts the sample pulse VS in the vertical synchronization period of the color signal G.

The delay signal generation circuit 12 has the mixer 11
The first and second horizontal scanning periods delayed from the green color signal G output from the first and second horizontal scanning periods, respectively.
And outputs the first and second delayed color signals to the clamp circuits 13 and 14, respectively. The clamp circuit 13 clamps the first delayed color signal, and the subsequent blanking cleaner 15 blanks the blanking pulse BLK during the blanking period of the first delayed color signal.
Replace with and output. As a result, the contour correction signal generation circuit 8 causes the delay signal generation circuit 12 to output the first delayed color signal G1.
To generate the first delayed color signal G1 and the clamp circuit 1
3. The blanking cleaner 15 shapes the waveform.

On the other hand, the clamp circuit 14 clamps and outputs the second delayed color signal, whereby the contour correction signal generation circuit 8 causes the delayed signal generation circuit 12 to generate the second delayed color signal G2. The clamp circuit 14 shapes the waveform of the second delayed color signal G2.

The vertical correction signal generation circuit 17 defines the first delayed color signal G1 as the color signal of the main line, and subtracts the original color signal G from the color signal of the main line to obtain the first contour correction signal. Generate the ingredients. Further, the vertical correction signal generation circuit 1
Reference numeral 7 denotes the main line color signal G1 to the second delayed color signal G2.
Generate a second contour correction component by subtracting
The first and second contour correction components are added to generate the vertical contour correction signal VDTL.

The comb filter 18 removes the chroma band signal components from the original green color signal G, the first delayed color signal G1, the second delayed color signal G2, and the red color signal R, respectively. Effectively avoid the occurrence of cross color.
The adder circuit 19 adds the green color signal G, the first delayed color signal G1, the second delayed color signal G2, and the red color signal R output from the comb filter 18 and outputs the result.

Here, in this embodiment, the green color signal G
The solid-state image pickup device 4G that outputs the red color signal R and the blue color signal B that are output are arranged pixel-shifted, thereby improving the spatial frequency in the television camera 1. It is done like this. For this reason, the contour correction signal generation circuit 8 has the addition circuit 19
, The green color signal G, the first delayed color signal G1, the second
Not only the delayed color signal G2 but also the red color signal R is added, thereby compensating the resolution of the green color signal G, the first delayed color signal G1, and the second delayed color signal G2.

The horizontal correction signal generating circuit 20 delays the output signal of the adding circuit 19 by a predetermined period to generate first and second delayed signals, and the first and second delayed signals are the original signals. By adding and subtracting with the output signal,
A horizontal contour correction signal HDTL is generated. Thus, in the contour correction signal generation circuit 8, the level adjustment circuit 21 adjusts the levels of the vertical contour correction signal VDTL and the horizontal contour correction signal HDTL and adds them.

The amplifier circuit 22 has the level adjusting circuit 21.
The output signal of 1 is amplified and output with a predetermined gain, and the clipping circuit 23 removes the noise component from the output signal by clipping the output signal of the amplifier circuit 22 and outputs the output signal. The variable gain amplifier circuit 24 amplifies and outputs the output signal of the clipping circuit 23, and the level adjusting circuit 25 adjusts the level. As a result, the contour correction signal generation circuit 8 generates an entire contour correction signal from the vertical and horizontal contour correction signals VDTL and HDTL, and then performs waveform shaping and level adjustment of the generated contour correction signal. Has been done.

Further, in this embodiment, an aperture signal is added to the contour correction signal generated in this way so that the contour correction circuit 6 also compensates the high frequency band of the video signal SV. That is, the delay circuit 27 delays the output signal of the adder circuit 19 by about 30 [nsec] and outputs it. The amplifier circuit 28 amplifies the output signal of the adder circuit 19 with a specified gain and outputs it. Level adjustment circuit 29
Adjusts the level of the output signal of the delay circuit 27 and the level of the output signal of the amplifier circuit 28, and then performs subtraction processing, whereby the contour correction signal generation circuit 8 extracts high frequency components from the output signal of the addition circuit 19. Generate an aperture signal.

The delay circuit 30 delays this aperture signal by about 110 [nsec] to match the timing of this aperture signal with the output signal of the clipping circuit 23. The level adjusting circuit 31 adjusts the level of this aperture signal and outputs it to the mixer (MIX) 32, and the mixer 32 adds the output signal of the level adjusting circuit 31 to the output signal of the level adjusting circuit 25 and outputs it.
As a result, the contour correction signal generation circuit 8 adds the aperture signal to the contour correction signal and adds the final contour correction signal DTL.
The blanking cleaner 33 replaces the blanking period of the contour correction signal DTL with the blanking pulse BLK and outputs the blanking pulse BLK.

Thus, as described above with reference to FIG.
In the contour correction circuit 7, the contour correction signal DTL is added to each color signal G1, R, B to emphasize the contour of the video signal SV.

As shown in FIG. 1, the delay signal generation circuit 12 of the contour correction signal generation circuit 8 converts the green color signal G into a digital signal in an analog-digital conversion circuit (A / D) 40. And outputs it to the line memory 41, where it is delayed by the delay time TDL1. The digital-analog conversion circuit (D / A) 42 converts the digital signal output from the line memory 41 into an analog signal and outputs the analog signal, and the low-pass filter (LPF) 43.
Outputs the output signal of the digital-analog conversion circuit 42 after band limiting.

In this embodiment, the delay time TDL1 of the line memory 41 is Ta, the delay time of the analog-digital conversion circuit 40 is T, the delay time of the digital-analog conversion circuit 42 is Tb, and the delay time of the low-pass filter 43 is Tc. And the following formula

[Equation 1] The total delay time T1 represented by the relational expression is selected so as to be one horizontal scanning period, whereby the output signal of the low pass filter 43 is output as the first delayed color signal G1.

Thus, the delay time TDL1 of the line memory 41 is obtained by transforming the equation (1) into the following equation.

[Equation 2] The delay time represented by is selected.

Further, the delay signal generation circuit 12 inputs the digital signal output from the line memory 41 to the line memory 45, delays it by the delay time TDL2, and then converts it into an analog signal by the digital-analog conversion circuit 46. . The low-pass filter 47 band-limits the output signal of the digital-analog conversion circuit 46 and outputs it.

Here, the delay time T of the line memory 45 is
DL2 is selected for one horizontal scanning period T1. Therefore, in this embodiment, the second delayed color signal G2 delayed by two horizontal scanning periods T2 from the original green color signal G via the low pass filter 47 is selected. It is designed to generate.

That is, the digital-analog conversion circuit 46
, And the delay time of the low-pass filter 47 is Te, the delayed color signal G with respect to the original green color signal G is
The delay time T2 of 2 is

(Equation 3) It is represented by. Substituting equation (2) into equation (3),
The following formula

[Equation 4] The following relational expression is obtained. Here, between the delay times Tb and Td of the digital-analog conversion circuits 42 and 46 and the delay times Tc and Te of the low-pass filters 43 and 47,
The following formula

(Equation 5) Since the relational expression of

(Equation 6) Can be transformed like.

This gives the following equation

(Equation 7) And the delay time TDL2 is set to one horizontal scanning period T1.

(Equation 8) As shown by, it is possible to obtain the delayed color signal G2 delayed by two horizontal scanning periods T2 with respect to the original green color signal G.

At this time, in the delay signal generation circuit 12, when the green color signal G is converted into a digital signal and delayed by using the line memories 41 and 45, a delay signal is generated using the glass delay line. The problems of can be solved all at once.

That is, the line memories 41 and 45 can manage the clocks by transferring and delaying the input data sequentially by using the clocks as a reference to manage the delay time easily and with high accuracy. Therefore, it is possible to effectively avoid variations and changes in the delay time, and it is possible to effectively avoid the deterioration of registration as in the case of using the glass delay line. Also, unnecessary reflection can be effectively avoided. Furthermore, deterioration of frequency characteristics and insertion loss can be reduced, and the entire structure can be simplified by omitting the correction circuit as in the case of using the glass delay line.

Therefore, as a whole television camera,
By effectively utilizing the advantages of forming the signal processing circuit with an analog circuit, the problems of using a glass delay line can be effectively avoided, and the overall performance is improved compared to the conventional one. You can

In the above-mentioned structure, the image of the subject obtained through the zoom lens 2 is the solid-state image pickup devices 4R and 4R.
G, 4B are converted into red, green, and blue color signals R, G, B, respectively, and the color signals R, G, B are processed by the signal processing circuit 5, and then the video signal SV is output by the subsequent encoder 6. Is converted to and output (FIG. 2). When signal processing is performed by the signal processing circuit 5, the contour correction signal DTL generated by the contour correction signal generation circuit 8 is added to the red, green, and blue color signals R, G, B, whereby the contour is emphasized. To be done.

Of these, the green color signal G is converted into a digital signal in the delay signal generation circuit 12 and then output to the line memories 41 and 45 connected in series. The output signals of the line memories 41 and 45 are converted into analog signals by the digital-analog conversion circuits 42 and 46, whereby the green color signal G is output as 1
The first and second delayed color signals G1 and G2 delayed by the horizontal scanning period T1 and the two horizontal scanning periods T2 are generated (FIG. 1).

The first and second delayed color signals G1 and G
2 is a vertical correction signal generation circuit 1 together with the original green color signal G
The addition / subtraction processing is performed in step 7 to generate the vertical contour correction signal VDTL (FIG. 3). Further, the first and second delayed color signals G1 and G2 are added together with the original green color signal G and the red color signal R after the cross color components have been removed, and then added together in the horizontal correction signal generation circuit 20. The contour correction signal HDTL is generated.

As a result, the contour correction signals VDTL and HD
After being added by the level adjustment circuit 21, TL is subjected to processing such as clipping, added with the aperture signal by the mixer 32 and converted into a final contour correction signal DTL, and the contour is emphasized by this contour correction signal DTL. It

According to the above configuration, the green color signal is converted into a digital signal, delayed, and then converted into an analog signal again to generate a contour correction signal, whereby signal processing such as gamma correction is performed. Even in the case of executing in the form, it is possible to effectively avoid the deterioration of the registration and the like, and thereby improve the characteristics of the contour correction circuit.

In the above embodiment, the case where the digital-analog conversion circuit is provided immediately after the line memories 41 and 45 has been described, but the present invention is not limited to this.
Digital signal processing may be performed up to generation of the contour correction signal, and then digital-analog conversion may be performed.

Further, in the above-described embodiment, the case where the aperture signal is added to the contour correction signal for processing has been described. However, the present invention is not limited to this, and the addition of the aperture signal may be omitted if necessary. Good.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the television camera has been described, but the present invention is not limited to this, and is widely applied to various image pickup apparatuses such as a video tape recorder integrated with a camera. be able to.

[0048]

As described above, according to the present invention, a gamma correction or the like is performed by converting a video signal into a digital signal to generate a delay signal and generating an analog signal form contour correction signal from the delay signal. The characteristics of the contour correction circuit can be improved when the signal processing of (1) is executed in an analog signal format.

[Brief description of drawings]

FIG. 1 is a block diagram showing a delay signal generation circuit of a television camera according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of the television camera shown in FIG.

3 is a block diagram showing a contour correction signal generation circuit in the television camera of FIG.

[Explanation of symbols]

 1 Television camera 5 Signal processing circuit 6 Encoder 7 Contour correction circuit 8 Contour correction signal generation circuit 12 Delay signal generation circuit 17 Vertical correction signal generation circuit 20 Horizontal correction signal generation circuit 40 Analog-digital conversion circuit 41, 45 Line memory 42, 46 Digital-analog conversion circuit 43, 47 Low-pass filter

Claims (1)

[Claims] 1. An image pickup apparatus for converting an output signal of a solid-state image pickup device into a video signal after processing the signal by a signal processing circuit and outputting the image signal, wherein the signal processing circuit processes the output signal in an analog signal format. After doing
The contour correction signal generated by the contour correction signal generation circuit is added to emphasize the contour of the video signal, and the contour correction signal generation circuit converts the signal-processed output signal into a digital signal to output the output signal. The first and second delay signals respectively delayed by one horizontal scanning period and two horizontal scanning periods are generated, and the first delay signal, the second delay signal, and the output signal are subjected to addition / subtraction processing, and the contour is obtained. An image pickup apparatus, which generates a correction signal, delays the first delay signal by one horizontal scanning period, and generates the second delay signal.