JP4009626B2 - Endoscope video signal processor - Google Patents

Description

  The present invention relates to an endoscope video signal processing apparatus that performs signal processing on an imaging unit provided in an endoscope.

In recent years, electronic endoscopes equipped with imaging means have been widely adopted in various endoscopic examinations and the like.
When performing an endoscopic examination using an electronic endoscope, a simultaneous endoscope apparatus that performs color imaging using an imaging device including a color optical filter under white light; and 2. Description of the Related Art There is a field sequential endoscope apparatus that generates a color image by performing imaging under R, G, and B surface sequential illumination light using a monochrome image sensor, and the signal processing system is Different.
Further, for example, in Japanese Patent Application Laid-Open No. 2002-95635, blood vessel traveling in the depth direction in the vicinity of the mucosal surface layer, which is easily buried with optical information obtained in the case of normal visible light, using narrow-band illumination light is disclosed. An endoscope apparatus that can display a state or the like as image information that can be more easily identified is disclosed.

In the conventional example of the above publication, a narrow-band image is generated using a narrow-band illumination light in a frame sequence, so that a narrow-band illumination light is used instead of a R-, G-, and B-sequential illumination light. If changed, it is possible to obtain a narrow band image relatively easily without requiring a large change in the signal processing system.
On the other hand, FIG. 10 shows a configuration of a conventional video signal processing device 81 for a simultaneous electronic endoscope.
A color image pickup signal picked up by a charge coupled device (abbreviated as CCD) 83 having a color separation filter 82 is input to a CDS circuit 84 in the video signal processing device 81 and subjected to CDS processing to generate a baseband signal component. Extracted.

The output signal of the CDS circuit 84 is input to the A / D conversion circuit 85 and converted from an analog signal to a digital signal. This digital signal is input to a Y / C separation circuit 86, where it is separated into a luminance signal Y and a line sequential color signal (color difference signal) C.
The luminance signal Y is input to the selector 88 via the γ circuit 87 (this luminance signal is Yh) and is input to a first low-pass filter (abbreviated as LPF) 89. The LPF 89 is set in a wide band, and the luminance signal Yl in the band set by the LPF 89 is input to the first matrix circuit 90.
The color signal C is input to the synchronization circuit 92 (line-sequentially) via the second LPF 91. In this case, the second LPF 91 has a lower band than the first LPF 89.
The synchronization circuit 92 generates synchronized color difference signals Cr (= 2R−G) and Cb (= 2B−G), and the color difference signals Cr and Cb are input to the first matrix circuit 90.

The first matrix circuit 90 converts the luminance signal Yl and the color difference signals Cr, Cb into the three primary color signals R1, G1, B1, and outputs them to the γ circuit 93. The three primary color signals R2, G2, and B2 that have been γ-corrected by the γ circuit 93 are input to the second matrix circuit 94, and the second matrix circuit 94 converts the luminance signal Ynbi and the color difference signals RY and BY into the second matrix circuit 94. Converted.
In this case, the second matrix circuit 94 converts the three primary color signals R2, G2, and B2 into a luminance signal Ynbi and color difference signals RY and BY so as to have a natural color tone.
The luminance signal Ynbi output from the second matrix circuit 94 is input to the expansion circuit 95 via the selector 88, and the color difference signals RY and BY are input to the expansion circuit 95. The selector 88 selects the luminance signal Yh subjected to γ correction from the Y / C separation circuit 86 and the luminance signal Ynbi input through the second matrix circuit 94 and outputs the selected luminance signal Ynbi to the enlargement circuit 95.

The luminance signal Yh / Ynbi enlarged by the enlargement circuit 95 is input to the third matrix circuit 97 via the enhancement circuit 96, and the color difference signals RY and BY enlarged by the enlargement circuit 95 are enhanced. The signal is input to the third matrix circuit 97 without passing through the circuit 96.
Then, the third matrix circuit 97 converts the signals to the three primary color signals R, G, B and outputs them to a color monitor (not shown).
Note that the selector 88 selects the luminance signal Yh side in the case of normal light observation with normal light, and the luminance signal that has passed through the second matrix circuit 94 in the case of narrow band light observation with illumination of narrow band light. That is, Ynbi is selected.
In this conventional video signal processing device 81, in order to perform signal processing conforming to the standard of a standard video signal, the luminance signal Y is subjected to wideband signal processing, and the color signal C is processed. Low-band signal processing was performed.
JP 2002-95635 A

In the conventional example shown in FIG. 10, the image quality in the normal light observation can be ensured, but in the narrow-band light observation, there is a defect that the image is processed as a low-band color signal and the resolution is low.
Furthermore, during narrow band light observation (NBI observation), there is a problem that the observation image becomes dark because the illumination light is narrowed.

(Object of invention)
The present invention has been made in view of the above-described points, and provides an endoscope video signal processing apparatus that can cope with normal light observation and obtain an endoscopic image with good image quality even during narrow-band light observation. For the purpose.

According to the present invention, an output signal from an imaging unit provided with a color separation optical filter for performing color imaging mounted on an endoscope is separated into a luminance signal and a color difference signal by a color separation unit. In an endoscope video signal processing apparatus that performs signal processing to generate a video signal of
In response to switching from the case of the illumination light in the visible region to the signal processing in the case of the narrow band illumination light, the processing characteristic changing means for changing the processing characteristics for the color separated signals by the color separating means, the color Band limiting means for performing band limitation on the color difference signal separated by the separating means, and
When the illumination light in the visible region is switched to illumination light in a narrow band, the processing characteristic changing unit changes the characteristic of the pass band by the band limiting unit to a wide band.

  According to the present invention, it is possible to deal with the case of illumination light in the visible region, and at the time of signal processing for the case of narrow-band illumination light, an image with good image quality can be obtained by changing the processing characteristics.

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

1 to 8 relate to a first embodiment of the present invention, FIG. 1 shows a configuration of an endoscope apparatus including the first embodiment of the present invention, and FIG. 2 shows a color separation filter provided in a solid-state image sensor. FIG. 3 shows an example of spectral characteristics of the narrowband filter, FIG. 4 shows a flowchart for explaining the operation of the present embodiment, FIG. 5 shows a signal band in the luminance signal and the color difference signal, and FIG. 6 shows the coefficients of the second matrix circuit set in the first modification in consideration of the characteristics of FIG. 5, FIG. 7 shows the spectral characteristics of the narrowband filter in the second modification, and FIG. The coefficient of the 2nd matrix circuit set in the case of 7 is shown.
As shown in FIG. 1, an endoscope apparatus 1 having Example 1 includes an electronic endoscope (hereinafter simply abbreviated as an endoscope) 2 that is inserted into a body cavity or the like and performs endoscopy, As an endoscope video signal processing device that drives a light source device 3 that supplies illumination light to the endoscope 2 and an imaging means built in the endoscope 2 and performs signal processing on an output signal of the imaging means. A video processor 4 and a monitor 5 that displays an endoscopic image captured by the imaging means when a video signal output from the video processor 4 is input are provided.

The endoscope 2 includes an elongated insertion portion 7, an operation portion 8 provided at the rear end of the insertion portion 7, and a universal cable 9 extending from the operation portion 8. The light guide connector 11 at the end of this is detachably connected to the light source device 3, and the signal connector is detachably connected to the video processor 4.
A light guide 13 that transmits illumination light is inserted into the insertion portion 7, and the light guide connector 11 at the end on the hand side of the light guide 13 is connected to the light source device 3. Illumination light is supplied to the light guide 13.
In the normal light observation mode, the light source device 3 generates white light (visible region) illumination light as normal illumination light and supplies it to the light guide 13, and in the narrow band light observation mode, the narrow band illumination light is supplied. Generated and supplied to the light guide 13.

The switching instruction between the normal light observation mode and the narrow-band light observation mode can be performed by, for example, the mode change switch 14 such as a scope switch provided in the operation unit 8 of the endoscope 2. In addition to the scope switch provided in the endoscope 2, the mode change switch 14 may be constituted by a foot switch, or may be provided on the front panel of the video processor 4, or by a keyboard (not shown). You may comprise.
The switching signal by the mode switch 14 is input to the control circuit 15 in the video processor 4. When the switching signal is input, the control circuit 15 controls the filter insertion / removal mechanism 16 of the light source device 3. The normal illumination light and the narrow-band illumination light are selectively switched.
As will be described later, the control circuit 15 also performs control for switching the characteristics of the video signal processing system in the video processor 4 in conjunction with switching control of illumination light supplied from the light source device 3 to the light guide 13. Then, by switching the characteristics of the video signal processing system by the switching operation by the mode switch 14, signal processing suitable for the normal light observation mode and the narrowband light observation mode can be performed.

The light source device 3 incorporates a lamp 20 that generates illumination light, and the lamp 20 generates illumination light including a visible light region. The illumination light is incident on the diaphragm 22 after the infrared light is cut by the infrared cut filter 21 so that the illumination light is close to the wavelength band of substantially white light. The aperture of the diaphragm 22 is adjusted by a diaphragm driving circuit 23 and the amount of light passing therethrough is controlled.
The illumination light that has passed through the diaphragm 22 passes through the narrow band filter 24 (in the narrow band light observation mode) inserted into and removed from the illumination optical path by the filter insertion / removal mechanism 16 constituted by a plunger or the like, or the narrow band filter. Without passing through 24 (in normal light observation mode), the light is incident on the condensing lens 25, collected by the condensing lens 25, and incident on the end face on the hand side of the light guide 13, that is, the incident end face.
FIG. 3 shows an example of the spectral characteristics of the narrowband filter 24. The narrow band filter 24 exhibits a three-peak filter characteristic, and has, for example, narrow band transmission filter characteristic portions Ra, Ga, and Ba in red, green, and blue wavelength regions, respectively.

More specifically, the narrow-band transmission filter characteristic portions Ra, Ga, and Ba have bandpass characteristics having center wavelengths of 600 nm, 540 nm, and 420 nm, respectively, and a half width of 20 to 40 nm.
Accordingly, when the narrow band filter 24 is arranged in the illumination optical path, the three bands of narrow band illumination light transmitted through the narrow band transmission filter characteristic portions Ra, Ga, Ba are incident on the light guide 13.
On the other hand, when the narrow band filter 24 is not arranged in the illumination optical path, white light is supplied to the light guide 13.
Illumination light from the light guide 13 is transmitted to the distal end surface thereof by the light guide 13, and is emitted to the outside through an illumination lens 27 attached to an illumination window provided at the distal end portion 26 of the insertion portion 7. Illuminate the surface of living tissue.

The distal end portion 26 is provided with an observation window adjacent to the illumination window, and an objective lens 28 is attached to the observation window. The objective lens 28 forms an optical image by reflected light from the living tissue. A charge coupled device (abbreviated as CCD) 29 is disposed as a solid-state imaging device at the imaging position of the objective lens 28, and photoelectric conversion is performed by the CCD 29.
For example, a complementary color filter shown in FIG. 2 is attached to the image pickup surface of the CCD 29 for each pixel as a color separation filter 30 for optically color separation.
This complementary color filter has four color chips of magenta (Mg), green (G), cyan (Cy), and yellow (Ye) in front of each pixel, and Mg and G alternate in the horizontal direction. In the vertical direction, Mg, Cy, Mg, Ye and G, Ye, G, Cy are arranged in the order of arrangement.

In the case of the CCD 29 using this complementary color filter, two adjacent columns of pixels in the vertical direction are added and sequentially read out. At this time, the pixel columns are shifted and read in the odd and even fields. Then, the luminance signal and the color difference signal are generated as is well known by the color separation circuit on the subsequent stage side.
The CCD 29 is connected to one end of a signal line. By connecting a signal connector to which the other end of the signal line is connected to the video processor 4, the CCD driving circuit 31 and the CDS circuit 32 in the video processor 4 are connected. Connected to.
Each endoscope 2 includes an ID generation unit 33 that generates identification information (ID) unique to the endoscope 2, and the ID generated by the ID generation unit 33 is input to the control circuit 15, and the control circuit 15 Identifies the type of the endoscope 2 connected to the video processor 4 and the number of pixels of the CCD 29 built in the endoscope 2 by the ID.

Then, the control circuit 15 controls the CCD drive circuit 31 so as to appropriately drive the identified CCD 29 of the endoscope 2.
The CCD 29 receives the CCD drive signal from the CCD drive circuit 31 and inputs the photoelectrically converted imaging signal to a correlated double sampling circuit (abbreviated as CDS circuit) 32. A signal component is extracted from the imaging signal by the CDS circuit 32 and converted into a baseband signal, which is then input to the A / D conversion circuit 34, converted into a digital signal, and input to the brightness detection circuit 35. , Brightness (average luminance of the signal) is detected.
The brightness signal detected by the brightness detection circuit 35 is input to the dimming circuit 36, and a dimming signal for dimming is generated based on the difference from the reference brightness (target dimming value). The dimming signal from the dimming circuit 36 is input to the aperture driving circuit 23, and the aperture amount of the aperture 22 is adjusted so that the reference brightness is obtained.

The digital signal output from the A / D conversion circuit 34 is input to the Y / C separation circuit 37, and the luminance signal Y and the line-sequential color difference signal Cr (= 2R-G) (as the color signal C in a broad sense), Cb (= 2B-G) is generated. The luminance signal Y is input to the selector 39 via the γ circuit 38 (this luminance signal is referred to as Yh), and is also input to a first low-pass filter (abbreviated as LPF) 41 that limits the passband of the signal. .
The LPF 41 is set to have a wide pass band corresponding to the luminance signal Y, and the luminance signal Y 1 in the band set by the pass band characteristic of the LPF 41 is input to the first matrix circuit 42.
Further, the color difference signals Cr and Cb are input to the synchronization circuit 44 (line-sequentially) through the second LPF 43 that limits the pass band of the signal.
In this case, the passband characteristic of the second LPF 43 is changed by the control circuit 15 according to the observation mode. Specifically, in the normal light observation mode, the second LPF 43 is set to a lower band than the first LPF 41 .

On the other hand, in the narrow band light observation mode, the second LPF 43 is changed to a wider band than the low band in the normal light observation mode. For example, the second LPF 43 is set (changed) in a wide band almost like the first LPF 41. As described above, the second LPF 43 forms processing characteristic changing means for changing the processing characteristic for limiting the pass band for the color difference signals Cr and Cb in conjunction with the switching of the observation mode.
The synchronization circuit 44 generates synchronized color difference signals Cr and Cb, and the color difference signals Cr and Cb are input to the first matrix circuit 42.
The first matrix circuit 42 converts the luminance signal Y and the color difference signals Cr, Cb into the three primary color signals R, G, B, and outputs them to the γ circuit 45.
The first matrix circuit 42 is controlled by the control circuit 15 to change the matrix coefficient value (determining the conversion characteristics) according to the characteristics of the color separation filter 30 of the CCD 29 and the characteristics of the narrowband filter 24. Thus, the signals are converted into three primary color signals R1, G1, and B1 with no color mixture or almost no color mixture.

For example, the characteristics of the color separation filter 30 of the CCD 29 mounted on the endoscope 2 may differ depending on the endoscope 2 that is actually connected to the video processor 4. The coefficient of the first matrix circuit 42 is changed according to the characteristics of the color separation filter 30 of the CCD 29 that is actually used. By doing so, it is possible to appropriately cope with different types of imaging means that are actually used, preventing the generation of false colors, or converting the signals to the three primary color signals R1, G1, and B1 having no color mixture. Can do.
In addition, by generating the three primary color signals R1, G1, and B1 having no color mixture, particularly in the narrowband light observation mode, the color signal captured under the narrowband light of a specific color is a narrowband light of another color. It is possible to effectively prevent the color signal picked up below from being difficult to identify.

That is, in the conventional example shown in FIG. 10, a plurality of image components picked up under each narrowband light set in each of the R, G, and B wavelength bands are mixed, and the specific identification of interest However, in this embodiment, it is possible to prevent color mixing that causes such ambiguity.
In addition, by preventing this color mixture, on the subsequent stage side, the ratio of the image component corresponding to the specific narrow band light of interest is increased, or only the image component corresponding to the specific narrow band light of interest is displayed. It is also possible to perform display using the image, and it is also possible to perform image display that clearly reflects the characteristics of the image component corresponding to the specific narrow band light of interest.

The γ circuit 45 is also controlled by the control circuit 15. Specifically, in the narrow-band light observation mode, the γ characteristic is changed to emphasize the γ correction characteristic than in the normal light observation mode. As a result, the contrast on the low signal level side is enhanced, and the display characteristics are more easily identified. The three primary color signals R2, G2, and B2 that have been γ-corrected by the γ circuit 45 are input to the second matrix circuit 46, and by the second matrix circuit 46, the luminance signal Y and the color difference signals RY and BY are obtained. Is converted to
In this case, in the normal light observation mode, the control circuit 15 matrixes the second matrix circuit 46 so as to simply convert the three primary color signals R2, G2, and B2 into the luminance signal Y and the color difference signals RY and BY. Set the coefficient.
In the narrow-band light observation mode, the control circuit 15 changes the matrix coefficient of the second matrix circuit 46 from the value in the normal light observation mode, and the ratio (weighting) from the three primary color signals R2, G2, B2 to the B signal in particular. The luminance signal Ynbi and the color difference signals RY and BY are generated.

The conversion formula in this case is as follows using the matrix A and K of 3 rows and 3 columns.

Here, K is composed of, for example, three real number components k1 to k3 (the other components are 0), and the G and B color signals with respect to the R color signal by the conversion formula (1). The weighting (ratio) of the B color signal is particularly maximum. In other words, the R color signal having a long wavelength is suppressed, and the B color signal on the short wavelength side is emphasized.
A is a matrix for converting RGB signals into Y color difference signals, and the following known calculation coefficient (2) and the like are used.

  The luminance signal Ynbi output from the second matrix circuit 46 is input to the selector 39. Switching of the selector 39 is controlled by the control circuit 15. That is, the luminance signal Yh is selected in the normal light observation mode, and the luminance signal Ynbi is selected in the narrow band light observation mode.

The color difference signals RY and BY output from the second matrix circuit 46 are input to the enlargement circuit 47 together with the luminance signal Yh or Ynbi (denoted as Yh / Ynbi) that has passed through the selector 39.
The luminance signal Yh / Ynbi enlarged by the enlargement circuit 47 is subjected to edge enhancement by the enhancement circuit 48, and then input to the third matrix circuit 49, and the color difference signals RY, B that have been enlarged by the enlargement circuit 47. -Y is input to the third matrix circuit 49 without passing through the emphasis circuit 48.
Then, after being converted into the three primary color signals R, G, and B by the third matrix circuit 49, it is converted into an analog video signal by a D / A conversion circuit (not shown) and outputted to the monitor 5 from the video signal output terminal.

  Note that the emphasis circuit 48 may change the emphasis characteristics (whether the emphasis band is a middle or low band or a middle or high band) according to the type of the CCD 29, the color separation filter 30, and the like.

In particular, in the narrow-band light observation mode, the luminance signal Ynbi is enhanced. In this case, when the formula (1) is adopted, as will be described later, the processing of emphasizing structures such as capillaries near the living body surface layer by the B signal is performed, so that the image component of interest can be clearly displayed. become.
Note that the three primary color signals R, G, and B that are actually input from the video signal output terminal to the R, G, and B channels of the monitor 5 are in the narrow-band light observation mode, when the formula (1) is adopted, G, B, and B signals (weighting varies depending on the coefficient), especially the ratio due to the B signal is the largest, and it is easy to identify an endoscopic image corresponding to a structure such as a capillary vessel near the living body surface by the B signal. It can be displayed in the state.
That is, the signals input to the RGB channels of the monitor 5 in the narrow-band light observation mode are actually G, B, and B signals (apart from the coefficient values).

As described above, in the present embodiment, the signal processing system of the video processor 4 (more specifically, the Y / C separation circuit 37 and later) so that signal processing suitable for each observation mode can be performed in conjunction with switching of the observation mode. The processing characteristic changing means for changing the processing characteristics in the signal processing system) is formed.
In this case, instead of providing a dedicated processing circuit for each observation mode, it is possible to perform processing suitable for both observation modes by changing the processing characteristics in the almost common processing circuit, so that both processes can be performed with a simple configuration. It is characterized by being able to respond appropriately to the observation mode.

The effect | action by a present Example is demonstrated below with reference to FIG.
The operator connects the endoscope 2 to the light source device 3 and the video processor 4 as shown in FIG. 1 and turns on the power, whereby the control circuit 15 of the video processor 4 starts the initial setting process. As shown in step S1, as the operation mode of the light source device 3 and the video processor 4, for example, the normal light observation mode is set.

In this state, the light source device 3 is set in a state in which the narrowband filter 24 is detached from the illumination optical path as shown by the solid line in FIG. 1 and is imaged by the endoscope 2 under white illumination light. It will be in the state to perform. In addition, each unit on the video processor 4 side is also set to perform signal processing in the normal light observation mode.
The surgeon can perform an endoscopic examination by inserting the insertion portion 7 of the endoscope 2 into the body cavity of the patient. When the operator wants to observe in more detail the running state of the blood vessels on the surface of the tissue to be examined such as the affected part in the body cavity, the operator operates the mode switch 14.
As shown in step S2, the control circuit 15 monitors whether or not the mode change switch 14 has been operated. If the mode change switch 14 has not been operated, the control circuit 15 maintains that state, and the mode change switch 14 has been operated. If so, the process proceeds to the next step S3.

In step S3, the control circuit 15 changes the operation mode of the light source device 3 and the video processor 4 to the setting state of the narrowband light observation mode.
Specifically, the control circuit 15 controls the light source device 3 so that the narrowband filter 24 is arranged in the illumination optical path as indicated by a two-dot chain line in FIG. As shown in FIG. 2, the narrow band filter 24 is arranged in the illumination optical path so that illumination is performed by the narrow band illumination light by the narrow band transmission filter characteristic portions Ra, Ga, Ba.
Further, the control circuit 15 changes the setting of each unit in the video processor 4. Specifically, the control circuit 15 widens the band characteristic of the LPF 43 so that color mixing does not occur in the matrix coefficient of the first matrix circuit 42. And the γ characteristic of the γ circuit 45 is changed, and the matrix coefficient of the second matrix circuit 46 is changed in particular so that the ratio of the signal component by the color signal B (by the narrowband transmission filter characteristic unit Ba) becomes large, Further, change setting such as switching the selector 39 so that the luminance signal Ynbi is selected is performed.

By performing such a change setting, for example, in the narrowband light observation mode, for example, the matrix coefficient of the second matrix circuit 46 is changed to a processing characteristic that particularly increases the ratio of the signal component by the B color signal. It is possible to display in a state where the running state of capillaries in the vicinity of the surface layer of the biological tissue obtained from the B color signal imaged under the B illumination light by the transmission filter characteristic unit Ba can be easily identified.
In addition, since the band characteristics of the signal passage of the LPF 43 are widened, the traveling state of the capillaries and the G color signal imaged under the G illumination light close to the luminance signal by the narrow band transmission filter characteristic unit Ga. The resolution (resolution) of the blood vessel running state near the surface layer obtained can be improved, and an image with good image quality that is easy to diagnose can be obtained.
In the next step S4, the control circuit 15 monitors whether or not the mode change switch 14 has been operated. If the mode change switch 14 has not been operated, the control circuit 15 maintains that state, and the mode change switch 14 has been operated. If so, the process returns to the next step S1.

According to this embodiment that operates in this way, the existing simultaneous color imaging function is maintained in the normal light observation mode, and the coefficient of each part in the video processor 4 is set even in the narrowband light observation mode. By changing the processing characteristics such as changing, it is possible to sufficiently secure the observation function in the narrow-band light observation mode.
In other words, it is possible to prevent a decrease in resolution in the conventional example and obtain an endoscopic image with a good resolution, and (in the conventional example, it is easy to be buried due to a signal imaged under R narrow-band illumination light, for example). It is possible to display the running state of the capillaries imaged under the narrow-band illumination light B) in a state where it is easier to identify clearly.
In addition, according to the present embodiment, by switching some processing characteristics in the signal processing system, it is possible to easily cope with both the normal light observation mode and the narrow band light observation mode. It becomes a very convenient and useful device.

Also in the light source device 3, a narrow band light source device can be easily formed by providing means for inserting / removing the narrow band filter 24 in / from the optical path in addition to the normal light illumination means.
Next, a first modification will be described. In the first embodiment, the multiplication process can be reduced by performing the calculation by the first matrix circuit 42 as follows.
The first matrix circuit 42 described above generates the three primary color signals R1, G1, and B1 from the input luminance signal Y and color difference signals Cr and Cb.
In this case, the matrix calculation expression by the first matrix circuit 42 is generally as follows using a matrix M (matrix coefficients m11 to m33) of 3 rows and 3 columns.

  On the other hand, the luminance signal Y and the color difference signals Cr and Cb input to the first matrix circuit 42 have characteristics as schematically shown in FIG.

When the calculation of the above equation (3) is performed, considering the ratio (ratio) of the contribution of the luminance signal Y and the color difference signals Cr and Cb to the R, G, and B bands in FIG. The ratio contributed by the color difference signal Cb in the R band in FIG. 5 is sufficiently small compared to the other and can be approximated to zero.
That is, the coefficient m13 can be approximated to zero. Further, the ratio contributed by the color difference signal Cr in the G band is sufficiently small and can be approximated to zero. That is, the coefficient m22 can be approximated to zero.
Further, the ratio contributed by the color difference signal Cr in the B band is sufficiently small compared to the other, and can be approximated to zero. That is, the coefficient m32 can be approximated to zero.
Therefore, the following can be adopted as the matrix M.

The coefficients of this matrix M are shown in FIG. Further, the coefficients of the matrix M may be approximated as shown in FIGS. 6B, 6C, and 6D from the characteristics shown in FIG. By approximating in this way, the configuration of the multiplier by the first matrix circuit 42 can be further reduced or simplified, and high-speed processing and cost reduction are possible.
Next, a second modification will be described. In the above description, the narrowband filter 24 employs a trimodal filter, but a bimodal filter may be employed as follows.
As the narrow band filter 24B in the second modification, a filter having transmission characteristics as shown in FIG. 7 may be adopted. This narrow band filter 24B is a bimodal filter, and has narrow band transmission filter characteristic parts Ga and Ba in the G and B wavelength regions, respectively. That is, the narrow band transmission filter characteristic portion Ra in the trimodal narrow band filter 24 in the first embodiment is not provided.

More specifically, the narrow-band transmission filter characteristic portions Ga and Ba have bandpass characteristics with center wavelengths of 420 nm and 540 nm, respectively, and a half width of 20 to 40 nm.
Accordingly, when the narrow band filter 24B is disposed in the illumination optical path, the two bands of narrow band illumination light that has passed through the narrow band transmission filter characteristic portions Ga and Ba are incident on the light guide 13.
In this case, the matrix calculation formula by the first matrix circuit 42 is generally as follows using a matrix M of 2 rows and 3 columns.

On the other hand, the luminance signal Y and the color difference signals Cr and Cb input to the first matrix circuit 42 have characteristics as shown in FIG. The coefficients m22 and m32 can be approximated to 0 by performing an approximation similar to that derived from Equation (4).
In this case,

It becomes. This is shown in FIG. Further, by performing other approximation methods, a matrix M of coefficients as shown in FIGS. 8B and 8C can be adopted.
Thus, by approximating some of the coefficients of the matrix M to 0, the number of multipliers can be reduced. Further, there is an effect that matrix calculation processing can be performed at higher speed. Furthermore, by using a bimodal filter, it is possible to reduce the cost of an expensive narrow band filter.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 shows an endoscope apparatus 1B provided with the second embodiment of the present invention.
The endoscope apparatus 1B has a configuration in which a video processor 4B in which a part of the video processor 4 in FIG. 1 is changed is employed. In this video processor 4B, the first matrix circuit 42, the γ circuit 45, and the second matrix circuit 46 in the video processor 4 of FIG.
Then, as described in the first embodiment, the control circuit 15 changes the γ characteristic of the γ circuit 45 and the matrix coefficient of the second matrix circuit 46 in accordance with the switching signal from the mode changeover switch 14. Change matrix coefficients.

When the matrix circuit 51 is switched from the normal light observation mode to the narrow-band light observation mode, the matrix circuit 51 suppresses color-free conversion, changes in γ characteristics, and color signals on the long wavelength side (converts color signals on the short wavelength side). The process of performing the emphasized conversion is collectively performed by changing the coefficient.
In addition, an AGC circuit 52 is provided between the A / D conversion circuit 34 and the Y / C separation circuit 37 for automatically gain-controlling the signal level of the input signal.
Further, the brightness detection circuit 35 receives the output signal of the CDS circuit 32 and the luminance signal Ynbi from the matrix circuit 51. Further, the control circuit 15 changes the AGC gain and the follow-up speed of the AGC circuit 52 according to the observation mode by switching the mode switch 14.

Specifically, in the narrow band light observation mode, the control circuit 15 sets the AGC gain of the AGC circuit 51 to be larger than that in the normal light observation mode, and for example, sets the follow-up speed of AGC gain control to the aperture 22 of the light source device 3. Set slower than the aperture control speed. In this way, the dimming operation by the diaphragm 22 is prioritized over the signal gain control operation by the AGC circuit 52.
In the light control circuit 36, the reference brightness (target value of light control) is also switched between the normal light observation mode and the special light observation mode.
In this way, the light control is performed by giving priority to the light control operation by the diaphragm 22 of the light source device. When the dimming operation cannot sufficiently perform dimming by the diaphragm 22, an automatic gain control operation by the AGC circuit 52 is supplementarily performed.

Specifically, if the brightness is not sufficient even when the aperture 22 is opened and the amount of illumination light is maximized, the AGC circuit 52 will function (before the aperture 22 is released). B) S / N can be prevented from deteriorating due to the operation of the AGC circuit 52, and an endoscopic image with appropriate brightness can be obtained.
According to the present embodiment, in addition to the operational effects of the first embodiment, it is possible to obtain an endoscopic image with appropriate brightness by preventing deterioration of S / N particularly in the narrow-band light observation mode.
Note that embodiments configured by partially combining the above-described embodiments and the like also belong to the present invention.

[Appendix]
1. 4. The conversion unit according to claim 3, wherein the conversion unit converts the luminance signal and the color difference signal into a three primary color signal having almost no color mixture.
2. 4. The method according to claim 3, further comprising second conversion means for converting the three primary color signals into a luminance signal and a color difference signal, and when the illumination light in the visible region is switched to illumination light in a narrow band. The conversion means changes the conversion characteristic to increase the weighting of the short wavelength color signal in the three primary color signals.
3. 2. The conversion device according to claim 1, further comprising a conversion unit configured to convert the luminance signal and the color difference signal separated by the color separation unit into a second luminance signal and a second color difference signal, and having a narrow band from the illumination light in the visible region. When switched to illumination light, the conversion means changes the conversion characteristic to increase the weighting of the short wavelength color signal.

4). In claim 1, when the illumination light in the visible region is switched to illumination light in a narrow band, the γ characteristic is changed.
5). In Claim 1, when the illumination light in the visible region is switched to illumination light in a narrow band, the enhancement characteristic by the enhancement unit is changed.
6). An output signal from an image pickup means provided with a color separation optical filter for color image pickup mounted on an endoscope is separated into a luminance signal and a color difference signal by a color separation means to generate a color video signal. A signal processing device for performing signal processing to be generated;
A light source device that switches between illumination light in a visible region and illumination light in a narrow band; and
In an endoscope apparatus comprising:
Intrasight characterized by comprising processing characteristic changing means for changing processing characteristics for signals color-separated by the color separation means in conjunction with switching between illumination light in the visible region and narrow-band illumination light Mirror device.

7). The supplementary note 6 further comprises a band limiting unit that performs band limitation on the color difference signal separated by the color separation unit, and the processing characteristic change is performed when the illumination light in the visible region is switched to illumination light in a narrow band. The means changes the characteristic of the pass band by the band limiting means to a wide band.
8). In Additional Statement 6, when the luminance signal and the color difference signal separated by the color separation means are converted into three primary color signals, when the illumination light in the visible region is switched to the narrow-band illumination light The processing characteristic changing means changes the conversion coefficient for determining the conversion characteristic by the converting means.
9. In Appendix 6, further comprising: a dimming signal generating means for controlling the amount of illumination light; and a gain control means for variably controlling the level of the video signal, wherein the operation of the dimming signal generating means is controlled by the gain control. Prioritized the action of the means.

  Can be used in normal light observation mode in which color imaging is performed under white illumination using an endoscope equipped with a color separation filter, and narrowband illumination light is inserted through a narrowband filter in the illumination optical path By changing the processing characteristics by changing the coefficients of the low-pass filter or matrix circuit, an image with good image quality can be obtained even in the narrow-band light observation mode.

1 is a block diagram showing a configuration of an endoscope apparatus including Example 1 of the present invention. The figure which shows the structure of the filter arrangement | sequence of the color separation filter provided in the solid-state image sensor. The characteristic view which shows the example of the spectral characteristic of the filter for narrow bands. The flowchart for operation | movement description of a present Example. The figure which shows the signal band in a luminance signal and a color difference signal. The figure which shows the coefficient of the 2nd matrix circuit set in a 1st modification in consideration of the characteristic of FIG. The characteristic view which shows the spectral characteristics of the filter for narrow bands in the 2nd modification. The figure which shows the coefficient of the 2nd matrix circuit set in the case of FIG. The block diagram which shows the structure of the endoscope apparatus provided with Example 2 of this invention. The block diagram which shows the structure of the video signal processing apparatus of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Endoscope apparatus 2 ... (Electronic) endoscope 3 ... Light source apparatus 4 ... Video processor 5 ... Monitor 7 ... Insertion part 8 ... Operation part 11 ... Light guide connector 13 ... Light guide 14 ... Mode switch 15 ... Control Circuit 16 ... Filter insertion / removal mechanism 20 ... Lamp 22 ... Aperture 23 ... Aperture drive circuit 24 ... Narrow band filter 28 ... Objective lens 29 ... CCD
DESCRIPTION OF SYMBOLS 30 ... Color separation filter 31 ... CCD drive circuit 32 ... CDS circuit 33 ... ID generation circuit 34 ... A / D conversion circuit 35 ... Brightness detection circuit 36 ... Dimming circuit 37 ... Y / C separation circuit 38, 45 ... gamma circuit 39 ... Selector 41, 43 ... LPF
42, 46 ... Matrix circuit 44 ... Synchronization circuit 47 ... Expanded circuit Agent Patent attorney Susumu Ito

Claims (3)

An output signal from an image pickup means provided with a color separation optical filter for color image pickup mounted on an endoscope is separated into a luminance signal and a color difference signal by a color separation means to generate a color video signal. In an endoscope video signal processing apparatus that performs signal processing to be generated,
Corresponding to switching from the case of illumination light in the visible region to the signal processing in the case of narrow-band illumination light, processing characteristic changing means for changing processing characteristics for the signals color-separated by the color separation means ;
Band limiting means for performing band limitation on the color difference signal separated by the color separation means;
Comprising
The video for an endoscope , wherein when the illumination light in the visible region is switched to illumination light in a narrow band, the processing characteristic changing unit changes the characteristic of the pass band by the band limiting unit to a wide band Signal processing device.   Furthermore, it has conversion means for converting the luminance signal and color difference signal separated by the color separation means into three primary color signals,
  The processing characteristic changing unit changes a conversion coefficient for determining a conversion characteristic by the conversion unit when the illumination light in the visible region is switched to illumination light in a narrow band. Endoscope video signal processing device.   Furthermore, it has a dimming signal generating means for controlling the amount of illumination light, and a gain control means for variably controlling the level of the video signal,
  2. The endoscope video signal processing apparatus according to claim 1, wherein the operation of the dimming signal generation unit is prioritized over the operation of the gain control unit.

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