JPH0336A - Electronic endoscope device - Google Patents

Abstract

PURPOSE:To prevent a color picture on a display screen from producing an unnatural feeling by providing a green killer circuit having a means to produce a clip level changed according to the level of a luminance signal and a means to effect clip in a negative direction on each of a plurality of a color signals by means of a clip level. CONSTITUTION:A clip level producing circuit 18 generates a clip level V from a luminance signal Y each time an OS signal from a photographing element 4 is separated into a luminance signal Y and color difference signals R-Y and B-Y by a color signal separating circuit 5. A clip level producing circuit 18 generates a clip level Vc from the luminance signal Y. Negative direction clip circuits 19 and 20 perform clip in a clip level on the color difference signals R-Y and B-Y, respectively, by means of a clip level Vc. A clip level producing circuit 18 to receive the luminance signal Y from the color signal separating circuit 5 generates the clip level Vc. The color difference signals R-Y and B-Y from the color signal separating circuit 5 are inputted to corresponding negative direction clip circuits 19 and 20, and green killer processing is effected by the negative direction clip circuits 19 and 20.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention has a configuration in which the output signal of an image sensor is separated into a luminance signal and a plurality of color signals, and predetermined signal processing can be performed. The present invention relates to electronic endoscope devices, and particularly to improvements in technology for color signal processing.

(Prior Art) As is well known, this type of electronic endoscope device is equipped with an image sensor such as a CCD at the tip of the endoscope, and the aperture of the optical system of the image sensor is variable. It is difficult to
This makes it difficult to control the light that enters the image sensor. Therefore, the intensity of the light incident on the imaging surface of the image sensor is too strong, and the incident light often causes halation.

On the other hand, in the output signal of the image sensor (hereinafter referred to as O8 signal), color information is multiplexed with the luminance signal as a modulated wave, so if the O8 signal becomes saturated and the amplitude of the color signal cannot be maintained, the result will be The color image on the display screen turns green.

In other words, as the brightness increases, normally the color becomes lighter and becomes white, but when the brightness becomes even higher, for the above-mentioned reason, what should be white becomes green, which becomes unnatural.

Therefore, even in conventional electronic endoscope devices of this type, a so-called green killer circuit is installed in a part of the color signal processing circuit, so that even if the light incident on the imaging surface of the image sensor causes halation, the display screen will not be displayed. It is now possible to prevent color images from turning green.

(Problem to be Solved by the Invention) However, the green killer circuit applied to this type of conventional electronic endoscope device turns off the color signal in response to whether the luminance signal level is higher than a predetermined level. Because it has a switching configuration in which it can be turned on or left on, it is possible to prevent the color image on the display screen from turning green if halation occurs in the light incident on the imaging surface of the image sensor. However, there was a problem in that the brightness and darkness of the image changed unnaturally.

In addition, in a TV camera used for boat fishing, a green killer circuit is configured with a variable gain amplifier that changes the gain of the color signal according to the brightness signal level, and this green killer circuit is used to eliminate green at high brightness. are widely adopted. However, in the case of the green killer circuit using the above-mentioned variable gain amplifier used in TV cameras, in order to apply it to an electronic endoscope device that separates color signals such as color difference, RGB, etc., it is necessary to separate each color signal. Since it is necessary to provide a variable gain amplifier, the characteristics of each variable gain amplifier must be made the same. Moreover, variable gain amplifiers are expensive, difficult to adjust, and unstable.

Therefore, the green killer circuit using the variable gain amplifier cannot be applied to electronic endoscope devices at present.

The present invention has been made in view of the above circumstances, and its purpose is to provide an electronic endoscope device having a green killer circuit that is easy to adjust and does not cause unnaturalness in color images on the display screen. Our goal is to provide the following.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention has an electronic internal structure configured to separate the output signal of an image sensor into a luminance signal and a plurality of color signals and perform predetermined signal processing. A green killer comprising: a means for generating a clip level that changes according to the level of the luminance signal; and a means for clipping each of the plurality of color signals in a negative direction using the clip level. The device is characterized by comprising a circuit.

(Function) In the electronic endoscope device according to the present invention, attention is paid to the fact that as the light incident on the image sensor becomes brighter, the plurality of color signals obtained from the O8 signal, specifically each color difference signal, becomes negative. However, as described above, a green killer circuit having a variable level clip circuit configuration that performs negative clipping with the clip level changed depending on the brightness is provided for each of the plurality of color signals. In this case, since the green killer circuit does not use a conventional switching system, the brightness of the color image on the display screen does not change unnaturally.

Moreover, since green can be removed at high brightness without having to make the characteristics uniform as in the case of using a variable gain amplifier, color adjustment can be performed easily and stably.

(Embodiment) FIG. 1 is a block diagram showing the main part configuration of an electronic endoscope device according to an embodiment of the present invention, and FIG. 2 is an external appearance of the electronic endoscope device according to this embodiment. It is a perspective view showing an outline.

The electronic endoscope device of this embodiment consists of an endoscope 1 and a main body 2, as shown in FIG. The scope distal end 3 of the 5° endoscope 1 is equipped with an image sensor 4 which is a CCD as shown in FIG. The device main body 2 also includes a color signal separation circuit 5, green killer circuits 6 and 7, A/D converters 8 to 10, a frame memory 11, D/A converters 12 to 14, a matrix RGB conversion circuit 15, an encoder 16, and a CRT. Equipped with 17 displays,
The color signal separation circuit 5 and the green killer circuit 6.7 constitute the main parts of the camera control unit (CCU).

The green killer circuit 6°7 in the CCU is
In this embodiment, as shown in FIG. 3, the function is constituted by a clip level generation circuit 18 and negative direction clip circuits 19 and 20. In other words, the green killer circuit 6 is a combination of a clip level generation circuit 18 and a negative clip circuit 19, and the green killer circuit 7 is a combination of a clip level generation circuit 18 and a negative clip circuit 20. .

In this functional configuration, the O8 signal from the image sensor 4 is sent to the color signal separation circuit 5 where it is separated into a luminance signal Y and color difference signals R-Y, B-.
Clip level generation circuit 18
generates a clip level Vc from the luminance signal Y, a negative clipping circuit 19 clips the color difference signal R-Y in the negative direction using the clip level Vc, and a negative clip circuit 20 clips the color difference signal B using the clip level Vc. -Y
Clips in the negative direction. Note that here, R is a red component and B is a blue component.

That is, the clip level generation circuit 18 which receives the luminance signal Y from the color signal separation circuit 5 generates the clip level Vc as schematically shown in FIG. At this time, the color difference signals R-Y and B-Y from the color signal separation circuit 5 are applied to the corresponding negative direction clipping circuits 19.20, and the green killer processing described later is executed by the negative direction clipping circuits 19.20. Ru. Here, the operating principle of the negative direction clipping circuits 19 and 20 used in this embodiment will be explained.

In addition, in this description, the negative direction clipping circuits 19 and 20 are simply referred to as clipping circuits.

Figure 5 shows the human output characteristics of the clip circuit, and in the input/output characteristics of Figure 5, even if the input is on the negative side of the reference level Vt, the output will not fall below the clip level Vc. do not have. When the input is higher than the clip level Vc, the input/output characteristics are similar to VX.

Next, FIG. 6 shows the input/output characteristics when the clip level Vc shown in FIG. 5 is changed. In this Figure 6, Vc1=Vc
3 indicates each clip level, V c
1 is when the clip level is set to zero, and Vc2. V
c3 is when the clip level is lowered. When a signal as shown in FIG. 7 is input to a clipping circuit having characteristics with clip levels of V c 1 to V c 3, as shown in FIG. 5, the clip level V
At the time of c 1 , even if there is a negative voltage in the human power, the output becomes zero. However, when the clip level is made low such as the grip level vC3, a negative voltage also appears in the output.

The negative direction clipping circuits 19 and 20 operate on the principle shown in FIGS. 5 to 8, and perform green killer processing as follows.

When the color difference signal RY as schematically shown in FIG. 9 is applied from the color signal separation circuit 5 to one negative direction clipping circuit, the negative direction clipping circuit 19 operates as follows.

The hatched area A in FIG. 9 is a green area caused by saturation of the O8 signal. This green area is erased when the clip level Vc and the color difference signal RY have the relationship schematically shown in FIG. 10 in the negative direction clipping circuit 19. That is, since the hatched portion B in FIG. 10 is at the clipped level, the output of the negative direction clipping circuit 19 becomes the processed color difference signal RY as schematically shown in FIG. That is, in FIG. 11, when the brightness is low as in the 01 part, the clip level Vc is lowered, so even if the color difference signal RY from the color signal separation circuit 5 is negative, it is output as is, whereas the high As the brightness increases, the clip level Vc also increases, so the
Unnecessary parts such as the second part are clipped. Moreover,
No equivalent operation is applied to the color difference signal RY above the clip level Vc. Therefore, as will be described later, it is possible to perform green killer processing in which the image on the CRT display 17 that displays the copy image has no difference in brightness or darkness.

Furthermore, the negative direction clipping circuit 20 also operates in the same manner as the negative direction clipping circuit 19, so a description thereof will be omitted.

In this way, the green killer circuit 6 in FIG.
, 7, the color difference signals R-Y, B-Y from the color signal separation circuit 5 are processed as described in accordance with FIGS. 3 to 11.
is processed. These processed color difference signals R-Y, B-Y
are sent to the A/D converters 9 and 10, and at the same time, the luminance signal Y from the color signal separation circuit 5 is sent to the A/D converter 8, so that the luminance signal Y and the color difference signals R-Y, B- Y is digitized and stored in frame memory 1
1 at the same time. Then, they are simultaneously read out under the read control of a controller (not shown), converted back into analog signals by the D/A converters 12 to 14, and sent to the matrix RGB conversion circuit 15. This matrix RGB conversion circuit 15 includes a D/A converter 1
Red (R), green (B), blue (B) from outputs 2 to 14.
), the subject image is displayed in color on the CRT display 17. Also, D/A
The outputs of the converters 12 to 14 are sent to an encoder 16 such as NTSC or PAL.

As described above, according to one embodiment of the present invention, the green killer circuit 6.7 functionally constituted by the clip level generation circuit 18 and the negative direction clip circuit 19.20,
Since the color signal is clipped in the negative direction, even if the light incident on the imaging surface of the image sensor causes halation, the color image on the display screen can be prevented from turning green.
By the processing of the green killer circuits 6 and 7 as schematically shown in FIG. 1, the brightness and darkness of the image can be changed naturally.

In addition, in the case of the conventionally adopted green killer circuit, since it is a switching method, as shown in Figure 12, the O
Since the processing waveform of the color signal changes unnaturally depending on the switching operation of N and OFF, the color difference signal R-
Even if color signals such as Y can be clipped in the negative direction, the brightness of the image changes unnaturally and becomes difficult to see.

〔Effect of the invention〕

As explained above, the electronic endoscope device of the present invention uses a green killer circuit that clips in the negative direction by changing the clip level depending on the brightness, so that the incident light on the image sensor is When halation occurs, the color image on the display screen can be prevented from turning green, and the brightness and darkness of the image can be changed so as not to lose its natural feel. Furthermore, since the present invention does not use a variable gain amplifier, there is no need to make the characteristics uniform for each color signal, so there are advantages such as extremely easy adjustment of the green killer circuit.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the main part configuration of an electronic endoscope device according to an embodiment of the present invention, Fig. 2 is a perspective view showing the outline of the external appearance of the electronic endoscope device, and Fig. 3 is a green endoscope device. Detailed explanation diagram of the killer circuit, Figure 4 is an output waveform diagram of the clip level generation circuit, Figures 5 to 8 are diagrams explaining the principle of the clip circuit,
Figure 9 is a color signal waveform diagram from the color signal separation circuit, Figure 10 is a diagram explaining the operation of the negative direction clipping circuit, Figure 11 is an output waveform diagram of the negative direction clipping circuit, and Figure 12 is a conventional green killer circuit. FIG. 1...Endoscope 2...Device body 3...Scope tip 4...Image sensor 5...Color signal separation circuit 6.7...Green killer circuit 8-10...A /D converter 11...Frame memories 12 to 14...D/A converter 15...Matrix RGB conversion circuit 16...Encoder 17...CRT display

Claims (1)

[Claims] (1) In an electronic endoscope device configured to separate an output signal of an image sensor into a luminance signal and a plurality of color signals and perform predetermined signal processing, a clip whose level is changed according to the level of the luminance signal. An electronic endoscope apparatus comprising: a green killer circuit having means for generating a level, and means for clipping each of the plurality of color signals in a negative direction based on the clip level.