JPH11136693A - Electron endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of an S/N with a simple structure and to provide a luminance reproducibility by generating a high band luminance signal from an image pickup signal outputted from a solid-state image pickup element, generating plural low band color signals, detecting a hue by using at least more than one low band color signal out of the low band color signals and correcting the high band luminance signal with a correction amount output corresponding to the hue. SOLUTION: A luminance generation part 20 generates a high band luminance signal YH from an image pickup signal by an LPF 21, and applies an outline compensation to the generated high band luminance signal YH by an enhancement circuit 22, whereas a γ correction circuit 23 executes a γ correction of a luminance element. A band pass filter 31 extracts a color carrier element from the image pickup signal, and generates a line sequential color difference signals CR/CB, while a 1H delay circuit 32 performs one horizontal period delay the line sequential color difference signals CR/CB, and a selector 33 switches for every horizontal period the delayed line sequential color difference signals CR/CB and the non-delayed line sequential color difference signals CR/CB thus a matrix circuit 34 converts them into primary colors RGB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus, and more particularly to an electronic endoscope apparatus characterized by a portion for generating a luminance signal based on an imaging signal from a solid-state imaging device having a complementary color filter.

[0002]

2. Description of the Related Art Conventionally, in a video signal processing circuit of an electronic endoscope apparatus, a subject is imaged by a solid-state image pickup device (hereinafter abbreviated as CCD) provided at the tip of an insertion section, and a video signal is processed in a video signal processing section. The generated and observed image is displayed on the monitor.

In a video signal processing circuit for processing an image signal from a single-plate type electronic endoscope having a complementary color filter in front of the CCD, as shown in FIG.
The low-pass filter (hereinafter abbreviated as LPF) 102 removes the color carrier component from the imaging signal read from 1 to obtain a high-band luminance signal YH. Also, L
The PF 103 has a cut-off frequency lower than that of the LPF 102, whereby the low-band luminance signal YL is used.
Is obtained. In the bandpass filter (BPF) 104, extraction of a color carrier component from the image signal is used, whereby a line-sequential color difference signal CR / CB is obtained.

The line-sequential color difference signals CR / CB are synchronized by the 1H delay line 105 and the selector 106 to obtain color difference signals CR (= 2R-G) and CB (= 2B-G). The YL, CR, and CB signals are supplied to the first matrix circuit 10.
7 and converted into primary color RGB signals by the following determinant.

[0005]

(Equation 1) In the above equation, K _{11 to} K ₃₃ are the connected CCD 101
In consideration of the spectral sensitivity characteristics described above, for example, when red is captured, the R signal is set to be large.

The white balance correction circuit 108 corrects a variation in the spectral sensitivity of the complementary color filter with respect to a change in the color temperature of the light source from the RGB signals of the primary colors.

The RGB signals after the white balance in the white balance correction circuit 108 are subjected to γ correction independently for R, G, and B in the γ correction circuit 109, and the second matrix circuit 110 performs the following NTSC The luminance signal YL ', the chrominance signal RY, and the BY signal are converted again by the conversion conforming to the standard of the system.

[0008]

(Equation 2) The luminance signal YL 'obtained by the second matrix circuit 110 has the following characteristics.

(1) Since luminance is generated from RGB signals after white balance correction, luminance reproducibility is good.

(2) Color mixing occurs due to the calculation with the color difference signal, and the S / N is poor.

On the other hand, after the high-band luminance signal YH is subjected to contour compensation by the enhancement circuit 111, the γ correction circuit 1
At 12, the luminance component is subjected to γ correction.

Here, the high-band luminance signal YH is C
Since it is obtained by removing the color carrier component from the image pickup signal of the CD 101, there is no color mixing of pixels and no deterioration of S / N occurs.

However, the spectral sensitivity characteristic depends on the spectral sensitivity of the complementary color filter and differs from the actual visual sensitivity of the eye, so that the luminance reproducibility is poor.

Therefore, conventionally, the YL ′ signal, which has a poor S / N but good luminance reproducibility, is
This problem is remedied by adding to the YH signal, which has poor luminance reproducibility but good S / N, and the RY and BY signals by the encoder 114 and the corrected high-band luminance signal Y
It was converted to a video signal using H '.

However, as described above, the S / N of the YL 'signal is poor, and there is a problem that the luminance reproducibility and the S / N are traded off by the correction.

For example, in Japanese Patent Application Laid-Open No. 2-288574, a color evaluation means is provided, and a YH signal having a good S / N but poor luminance reproducibility and a YL signal having a poor S / N but good luminance reproducibility are provided. 'A proposal has been made to generate a correction signal by controlling the mixing ratio of the signals based on the hue, thereby preventing the S / N from deteriorating.

That is, the same components as those shown in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted. However, in Japanese Patent Laid-Open No. 2-288574, as shown in FIG. The color difference signal R obtained by the matrix circuit 110
-Y and BY are input to an evaluation circuit 121 to evaluate the color saturation, color temperature, and the like, and the evaluation results are added to an adder 12.
Output to 2. In the adder 122, the high-band luminance signal YH
And YL ′ are added at different mixing ratios according to the evaluation result. As a result, according to the color information of the subject, S
While taking advantage of the YH signal with good / N and the YL 'signal with high luminance reproducibility, it is possible to obtain a luminance signal with little S / N deterioration and high luminance reproducibility.

[0018]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 2-288 is disclosed.
In Japanese Patent Application Laid-Open No. 574, 574, after performing white balance correction using the primary color RGB signals, the low band luminance signal Y
Attempts have been made to prevent S / N degradation by generating L 'and mixing it with the low-band luminance signal YL at a certain ratio to generate a correction amount.

However, there is a problem that means such as the evaluation circuit 121 and the adder 122 for selecting the mixture ratio become very complicated.

Further, since the degree of freedom of correction is low, there is also a problem that a sufficient correction cannot be obtained when paying attention to a specific hue. In particular, in a medical electronic endoscope apparatus, most subjects have a reddish hue, and luminance reproducibility is very important for a reddish hue. In many cases, a highly saturated red color, such as a bleeding part, is imaged from close-up. In such a case, the luminance reproducibility tends to be particularly impaired because the color reproducibility is emphasized. In such a case, if the luminance reproducibility is impaired, it is difficult to observe the undulation of the observation site, which may hinder the inspection.

The present invention has been made in view of the above circumstances, and provides a degree of freedom in luminance reproducibility for a desired hue, performs optimal correction in accordance with the hue, and implements a simple configuration.
It is an object of the present invention to provide an electronic endoscope apparatus that can prevent deterioration of / N and obtain high luminance reproducibility, and can improve diagnostic performance and safety in endoscopy.

[0022]

According to an electronic endoscope apparatus of the present invention, an electronic endoscope having a solid-state image sensor having a complementary color filter at a distal end of an insertion portion, and an image output from the solid-state image sensor are provided. An electronic endoscope apparatus comprising: a video signal processing unit configured to generate a video signal from a signal; a luminance signal generating unit configured to generate a high-band luminance signal from an imaging signal output from the solid-state imaging device; and the solid-state imaging unit. Color signal generation means for generating a plurality of low-band color signals from the imaging signal output from the, hue detection means for detecting hue using at least one or more low-band color signals of the low-band color signals, A correction amount generating unit that generates a correction amount corresponding to a hue using at least one or more low band color signals of the low band color signal; and receiving the output of the hue detecting unit and the correction amount generating unit, Band brightness Constructed and a luminance correcting means for correcting the signal.

In the electronic endoscope apparatus according to the present invention, the hue detecting means detects a hue using at least one of the low-band color signals among the low-band color signals, and the correction amount generating means detects the hue. A correction amount corresponding to the hue is generated using at least one or more low-band color signals of the band color signal, and the luminance correction unit receives the outputs of the hue detection unit and the correction amount generation unit, and receives the high-band luminance. By correcting the signal, the degree of freedom in luminance reproducibility for a desired hue is given, optimal correction is performed according to the hue, and the S / N is prevented from deteriorating with a simple configuration, and high luminance reproducibility is achieved. This makes it possible to improve diagnostic performance and safety in endoscopy.

[0024]

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

FIGS. 1 to 8 relate to an embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of an electronic endoscope apparatus, and FIG. 2 is a block diagram showing a configuration of a complementary color filter of FIG. 3 is a block diagram showing the configuration of the video signal processing device of FIG. 1, and FIG.
FIG. 5 is a configuration diagram showing a configuration of the correction amount generation circuit of FIG. 3, FIG. 6 is a configuration diagram showing a configuration of a modification of the hue detection circuit of FIG. 4, and FIG. FIG. 8 is a configuration diagram showing a configuration of a first modification of the correction amount generation circuit of FIG. 5, and FIG. 8 is a configuration diagram showing a configuration of a second modification of the correction amount generation circuit of FIG.

As shown in FIG. 1, an electronic endoscope apparatus 1 according to the present embodiment has a flexible insertion section 2 to be inserted into a body cavity and an operation section provided on the base end side of the insertion section 2. 3, an electronic endoscope 4 for imaging an observation site in a body cavity, a light source device 5 for supplying illumination light to the electronic endoscope 4, and a monitor 6 for processing image signals from the electronic endoscope 4 for signal processing. And a video signal processing device 7 for displaying an image of the observation site.

The electronic endoscope 4 is connected to a video signal processing device 7 by a universal cable 8 extending from the operation section 3, and further connected to a light source device 5 via a light guide cable 9.

The illumination light supplied from the light source device 5 is transmitted through the light guide cable 9, the universal cable 8 and the insertion section 2 of the electronic endoscope 4.
0 is transmitted to the distal end of the insertion portion 2 and the light guide 10
Are irradiated to an observation site (not shown) from the emission end surface of the light emitting device.

The optical image of the observation site is provided on the distal end surface of the insertion section 2 of the electronic endoscope 4 by a magenta (M) shown in FIG.
g), green (G), cyan (Cy), yellow (Y
The optical color separation is performed by a complementary color filter 11 for color coding in which the respective color filters are arranged, and then an image is formed on a light receiving surface of a solid-state imaging device, for example, a CCD 13 by an imaging lens 12.

The imaging signal obtained by the photoelectric conversion by the CCD 13 is transmitted to the video signal processing device 7 through a signal line (not shown) passing through the insertion section 2 and the universal cable 8.

As shown in FIG. 3, in the video signal processing device 7, the image pickup signal output from the CCD 13 is input to the luminance generation unit 20 and the color generation unit 30.

In the luminance generating section 20, the LPF 21 generates a high-band luminance signal YH from the image pickup signal,
The high-band luminance signal YH generated as described above is subjected to contour compensation by the enhancement circuit 22, and further to γ correction of the luminance component by the γ correction circuit 23.

The color generator 30 extracts a color carrier component from the image pickup signal by a band-pass filter (hereinafter, abbreviated as BPF) 31 and outputs a line-sequential color difference signal CR.
/ CB is generated.

Further, the color generator 30 includes a 1H delay circuit 3
2, the line sequential color difference signal CR / CB is delayed by 1H, and the line sequential color difference signal CR / CB delayed by the selector 33 and the line sequential color difference signal CR / CB that is not delayed by 1
Switch every H. Thereby, the line-sequential color difference signal C
R / CB is synchronized and output (CR, CB).

The CR and CB signals and the high-band luminance signal YH from which the color carrier component has been removed by the LPF 21 of the luminance generation section 20 are input to a first matrix circuit 34, and the primary color RGB signals are calculated by the following determinant. Is converted to

[0036]

(Equation 3) At this time, k _{11 to} k ₃₃ are set in consideration of the spectral sensitivity characteristics of the connected CCD 13 so that, for example, when an image of red is taken, the R signal becomes large.

The RGB signals obtained as described above are
The band is limited to a low band by the LPFs 35a, 35b, and 35c.

R through LPFs 35a, 35b and 35c
The GB signal is input to the white balance circuit 37, and the white balance circuit 37 adjusts the gain of the R and B signals so that R: G: B = 1: 1: 1 when capturing white. Thus, white balance is obtained with respect to a change in the color temperature of the light source.

The RGB signals subjected to white balance compensation by the white balance circuit 37 are output to the γ correction circuit 38, hue detection circuit 39, and correction amount generation circuit 40 at the next stage.

The gamma correction circuit 38 performs gamma correction on the color components and outputs the result to the second matrix circuit 41, which converts the color components into color difference signals RY and BY again.

The hue detection circuit 39, as shown in FIG.
The G signal input from the white balance circuit 37 is multiplied by k by a coefficient unit 39a to obtain a G 'signal, and the B signal is multiplied by m by a coefficient unit 39b to obtain a B' signal. The G ′ and B ′ signals are added by the adder 39c,
9d. The discrimination circuit 39d compares the G '+ B' added by the adder 39c with the magnitude of the R signal, and discriminates the hue by the following discriminant.

Discriminant: When R ≧ k × G + m × B, a correction instruction signal is generated. When R <k × G + m × B, no correction instruction signal is provided. As shown in FIG. The G signal input from the circuit 37 is multiplied by k by the coefficient unit 40a to obtain a G 'signal, and the B signal is multiplied by m by the coefficient unit 40b to obtain a B' signal. The G ′ and B ′ signals multiplied by the coefficients are added by an adder 40c,
is input to d. The adder 40d calculates the output of the adder 40c and the R signal, and generates the following signal C.

C = R− (k × G + m × B) Here, the case where k = m = 1 is considered. When the subject color is the primary red color, G = B = 0 and C = R. Next, when the subject color is yellow, R = G and B = 0, and C = RG−
It becomes 0. Similarly, when the subject is magenta, C = 0.

That is, when the subject color is red, the correction signal C has the maximum value R, and becomes smaller as approaching yellow or magenta. Further, when the color in the direction of G, Cy, B is obtained, R
Since G <B, C = 0. That is, the value of the correction signal C increases as the hue of the subject approaches R. The correction signal C is output as C 'after being n-times optimized by the coefficient unit 40e and optimized.

In the above-described configuration examples of the hue detection circuit 39 and the correction amount generation circuit 40, the coefficient units 39a and 40a, the coefficient units 39b and 40b, and the adder 39c
The operation of the adder 40c is the same as that of the adder 40c, so that the circuit can be simplified.

Returning to FIG. 3, the correction instruction signal obtained by the hue detection circuit 39 and the correction signal generation circuit 40
The output correction signal C ′ is input to the selector 42. The selector 42 outputs the correction signal C ′ to the luminance correction unit 43 only when a desired hue is detected based on the correction instruction signal from the hue detection circuit 39.

The luminance correction unit 43 calculates, for example, YH '= YH +
As in C ', the high-band luminance signal YH and the correction amount C' are added, and thereby the luminance level is corrected. Note that the luminance correction section 43 may be configured by a multiplier or the like, and the level may be corrected by setting YH ′ = YH × C ′.

Then, the corrected high-band luminance signal YH 'together with the chrominance signals RY and BY again obtained by the second matrix circuit 41 are simultaneously input to the encoder 44, and the standard television The signal is converted to a signal and output to the monitor 6.

As described above, in the present embodiment, the correction signal C ′ generated by the correction signal generation circuit 40 only when the desired hue detected by the hue detection circuit 39 is detected.
Is output to the luminance correction unit 43, and the luminance correction unit 43 adds the high-band luminance signal YH and the correction amount C ′ to correct the luminance level, so that the degree of freedom in luminance reproducibility for a desired hue is given. Optimum correction can be performed according to the hue, S / N can be prevented from deteriorating with a simple structure, and high luminance reproducibility can be obtained, and diagnostic performance and safety in endoscopy can be improved. it can.

In this embodiment, the hue is detected and the correction signal is generated based on the RGB signals after the white balance correction. However, the RGB signals before the white balance correction are generated.
It may be performed by a signal, or the second matrix circuit 41
This may be performed using the obtained color difference signals RY and BY. In any case, by detecting a desired hue and generating an optimal correction amount based on the hue,
Similar effects can be obtained.

As shown in FIG. 6, the multiplication coefficients u and v are controlled by control signals a and b from an external instruction means (not shown).
Coefficient units 51a and 52b can be changed to coefficient units 39a and 39b.
In this case, the hue to be corrected can be changed in the magenta direction and the Ye direction by changing the multiplication coefficients u and v.

Further, as shown in FIG. 7, a correction signal generating circuit 40 in which a coefficient unit 53 capable of varying the gain w by a control signal L from an external not shown indicating means may be used instead of the coefficient unit 40e may be used. In this case, by changing the gain of the coefficient unit 53 by the external control signal L,
The correction amount of the luminance component of the subject can be selected according to the viewer's preference.

As shown in FIG. 8, a noise reduction circuit 54 composed of an LPF or coring is provided between the adder 40d and the coefficient unit 40e to provide a correction signal generation circuit 4.
0 may be configured so that the correction signal C
Further, noise can be reduced.

[Supplementary note] (Supplementary note 1) An electronic endoscope having a solid-state imaging device having a complementary color filter at the tip of the insertion portion, and an image for generating a video signal from an imaging signal output from the solid-state imaging device In an electronic endoscope apparatus including a signal processing unit, a luminance signal generation unit configured to generate a high-band luminance signal from an imaging signal output from the solid-state imaging device, and a plurality of imaging signals output from the solid-state imaging unit. A color signal generating means for generating a low-band color signal; and at least one of the low-band color signals.
Hue detection means for detecting a hue by using one or more low-band color signals, and correction amount generation for generating a correction amount corresponding to the hue using at least one low-band color signal of the low-band color signals An electronic endoscope apparatus comprising: a luminance correction unit configured to receive the output of the hue detection unit and the correction amount generation unit and correct the high-band luminance signal.

(Additional Item 2) The color signal generation means has a white balance correction means, and converts the low band color signal before or after white balance correction into a primary color RGB signal or a color difference signal RY, 2. The electronic endoscope apparatus according to claim 1, wherein the electronic endoscope apparatus can be output as a BY signal.

[0056]

As described above, according to the electronic endoscope apparatus of the present invention, the hue detecting means detects the hue using at least one low-band color signal among the low-band color signals,
The correction amount generating means generates a correction amount corresponding to the hue using at least one or more low-band color signals of the low-band color signals, and the luminance correcting means receives the output of the hue detecting means and the correction amount generating means, and Since the band luminance signal is corrected, the degree of freedom in luminance reproducibility for a desired hue is given, optimal correction is performed according to the hue, and S / N is prevented from deteriorating with a simple configuration, and high luminance reproducibility is achieved. And the diagnostic performance and safety in endoscopy can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of an electronic endoscope apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a complementary color filter of FIG. 1;

FIG. 3 is a configuration diagram showing a configuration of the video signal processing device of FIG. 1;

FIG. 4 is a configuration diagram showing a configuration of a hue detection circuit of FIG. 3;

FIG. 5 is a configuration diagram showing a configuration of a correction amount generation circuit of FIG. 3;

FIG. 6 is a configuration diagram showing a configuration of a modification of the hue detection circuit of FIG. 4;

7 is a configuration diagram showing a configuration of a first modification of the correction amount generation circuit of FIG. 5;

8 is a configuration diagram showing a configuration of a second modification of the correction amount generation circuit of FIG. 5;

FIG. 9 is a configuration diagram showing a configuration of a video signal processing device of a first conventional example.

FIG. 10 is a configuration diagram showing a configuration of a video signal processing device of a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electronic endoscope apparatus 4 ... Electronic endoscope 5 ... Light source apparatus 6 ... Monitor 7 ... Video signal processing apparatus 11 ... Complementary color filter 13 ... CCD 20 ... Luminance generation parts 21, 35a, 35b, 35c ... LPF 22 ... Enhance Circuits 23, 38 γ correction circuit 30 Color generator 31 BPF 32 1H delay circuit 33, 42 Selector 34 First matrix circuit 37 White balance circuit 39 Hue detection circuits 39a, 39b, 40a, 40b , 40e... Coefficient units 39c, 40c, 40d... Adders 39d... Discrimination circuits 40... Correction amount generation circuits 41.

Claims (1)

[Claims] 1. An electronic endoscope having a solid-state imaging device having a complementary color filter at a distal end of an insertion portion, and a video signal processing unit for generating a video signal from an imaging signal output from the solid-state imaging device. In the electronic endoscope device, a luminance signal generating unit that generates a high-band luminance signal from an imaging signal output from the solid-state imaging device; and a plurality of low-band color signals from the imaging signal output from the solid-state imaging unit. A color signal generating means for generating; a hue detecting means for detecting a hue by using at least one low-band color signal among the low-band color signals; and at least one low band of the low-band color signal A correction amount generation unit configured to generate a correction amount corresponding to a hue using a color signal; and a luminance correction unit configured to receive the output of the hue detection unit and the correction amount generation unit and correct the high-band luminance signal. Electronic endoscope apparatus characterized by a.