JP3090164B2 - Electronic endoscope device - Google Patents

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 using a solid-state image pickup device, and more particularly to an electronic endoscope apparatus for imaging a subject under illumination light.

[0002]

2. Description of the Related Art An electronic endoscope used for medical or industrial purposes includes an endoscope main body, a processor, and a monitor device, and an insertion portion of the endoscope main body is inserted into a body cavity or the like. The illumination light is directed toward the subject from an illumination device built in or independent of the processor, the reflected image from the subject is photoelectrically converted by a solid-state imaging device such as a CCD, and the photoelectrically converted signal is transmitted to the processor. After performing signal processing in the processor, color display is performed on the monitor device.

Here, a single solid-state image sensor is used in order to reduce the diameter of the insertion portion of the scope section, and red (R), green (G), and blue ( The image of each color of B) is formed for each field, and the solid-state imaging device is driven by a so-called plane-sequential system in which the images are displayed by superimposing them. That is, in the field sequential method, the illumination light from the illumination lamp is converted to R,
Illumination with light of each color wavelength region of G and B is sequentially repeated, while charge accumulation and transfer are repeated for each illumination of each color in the solid-state imaging device, so that the R, G, and B color image signals are respectively divided for each field. In this method, a color video signal is created by forming these color image signals and converting them into simultaneous signals via R, G, B field memories.

[0004]

By the way, when driving a solid-state image pickup device to capture an image of a subject, in order to obtain a clear and high-quality image, the subject must be illuminated with an appropriate amount of illumination light. . However, the positional relationship between the end of the insertion section of the endoscope body provided with the illumination window and the observation window and the subject,
The appropriate illumination light amount is not constant depending on the reflectance of the subject and the like. For example, when the subject is at a distant position, the amount of light reflected from the subject decreases, so that the amount of light received by the solid-state image sensor decreases, and the monitor screen becomes dark. On the other hand, when the subject is in a close position, the amount of light received by the solid-state imaging device is too large, and the solid-state imaging device is immediately saturated, causing a so-called whiteout phenomenon, and detailed information on a white portion of the monitor image. Is missing, and the image quality also deteriorates.

Therefore, conventionally, there is provided a mechanism for adjusting the amount of illumination light emitted from an illumination lamp according to the position of a subject, the reflectance of light of the subject, and the like. The accompanying change in the amount of light received by the solid-state imaging device is adjusted. The mechanism for adjusting the amount of illumination light includes an aperture for mechanically controlling the illumination light, an aperture drive mechanism for driving the aperture, and a control circuit for controlling the aperture drive mechanism. The output signal of the solid-state imaging device is detected to extract luminance information therein, and the diaphragm driving mechanism is controlled so that the luminance information becomes a predetermined reference level. The light amount is being adjusted.

Incidentally, it is known that the amount of light of an illumination lamp such as a xenon lamp decreases with time.
When the amount of light decreases, a dark screen is obtained even when the aperture is opened. Therefore, there was a potential demand to use an expensive lamp for as long as possible and to observe the affected part clearly, but the lamp had to be replaced every 200 hours or so.

Further, depending on the subject to be observed,
The reflectance of light of each wavelength of R, G, and B is different. For example, in a medical endoscope which is inserted into a human body or the like and used for diagnosis and observation inside the body, the reflectance of light of a red wavelength component from a subject is extremely high, and green and blue light are emitted. Is absorbed on the object side, so that the amount of reflected red light becomes significantly larger than the amount of reflected light of other wavelengths, and a remarkable difference occurs in the amount of light received by the solid-state imaging device. Further, even in the case of an industrial endoscope, the reflectivity of light of wavelengths of R, G, and B greatly changes depending on the surface condition of a subject to be observed.

For this reason, among the R, G, and B color image signals formed in the solid-state imaging device, the specific signal level becomes too high and the width up to the saturation voltage is reduced, so that the dynamic range is reduced. In addition, the possibility of occurrence of a whitening phenomenon, blooming, smear, and the like increases. The present invention has been made in view of such circumstances,
It is an object of the present invention to provide an electronic endoscope apparatus that can adjust the sensitivity of a solid-state imaging device and can keep the luminance level of an output signal of the solid-state imaging device constant.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a method in which R, color-separated from a distal end of an endoscope in time series.
The illumination light of G and B is applied to the subject, the reflected image from the subject is received by the solid-state imaging device disposed at the end of the endoscope, and the R, G, and B signals sequentially output from the solid-state imaging device are output. An electronic endoscope apparatus for sequentially storing color image signals for each color in an image memory and simultaneously reading out R, G, and B color image signals from the image memory, wherein the solid-state imaging device is an OFD
In an electronic endoscope apparatus in which sensitivity changes according to an OFD voltage applied to an electrode, the sensitivity of the solid-state imaging device is set to R,
Setting means for setting each of the G and B illumination lights; and sensitivity control signals for R, G and B of voltages corresponding to the R, G and B illumination lights based on the settings made by the setting means. Means for outputting to the OFD electrode of the solid-state imaging device in synchronization with a vertical synchronization signal, and individually controlling the levels of R, G, and B color image signals sequentially output from the solid-state imaging device. Features.

[0010]

[0011]

[0012]

The present invention focuses on the fact that the sensitivity of the solid-state imaging device changes depending on the OFD voltage of the solid-state imaging device. The OFD voltage, which has been conventionally fixed at a constant voltage (10 to 12 V), is changed to R, G, B. Each color image signal,
Thereby, R, G, B sequentially output from the solid-state imaging device
Are individually adjusted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an electronic endoscope apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. First, the present invention will be described in principle. Generally, a solid-state imaging device accumulates light incident on a light receiving portion within a charge accumulation time. Some solid-state imaging devices have an OFD electrode.
When the voltage applied to the electrodes exceeds a certain level, there is a solid-state imaging device that releases accumulated charges to the drain and hardly outputs any power.

FIG. 2 shows the OFD power of such a solid-state imaging device.
5 is a graph illustrating an example of pressure-sensitivity characteristics, where the OFD voltage is
As the voltage rises, the sensitivity decreases due to a steep slope from a certain voltage,
Pressure V _tThe above shows that it has dropped to almost 0
ing. The OFD using such a solid-state imaging device
A predetermined level V is applied to the electrode._tPulse width with above voltage
Applies a controlled OFD pulse to the solid-state imaging device.
By changing the effective charge storage time,
Control of the sensitivity of the child, and the level of the R, G, B color image signal
Are controlled individually.

FIG. 1 shows a first embodiment of an electronic endoscope apparatus according to the present invention.
It is a block diagram showing an example. In the figure, reference numeral 10 denotes an illumination lamp (for example, a xenon lamp) that emits white light,
Reference numeral 14 denotes a light guide. This lighting lamp 10
The illumination light emitted from the light source enters the incident end 14A of the light guide 14 via the condenser lens 11, the aperture 12, and the rotating color filter 13, is transmitted by the light guide 14, and is transmitted from the exit end 14B to the illumination lens. The light is radiated toward the subject via the light source 16. In addition, the rotating color filter 1
Reference numeral 3 denotes an R filter region that transmits R (red) wavelength region light, a G filter region that transmits G (green) wavelength region light, and a B filter region that transmits B (blue) wavelength region light. By rotating the color filter 13, illumination is sequentially performed with light of each wavelength of R, G, and B.

The reflected image from the object illuminated in this way is transmitted through an objective lens 18 to a solid-state image pickup device (hereinafter, referred to as a solid-state image pickup device).
An image is formed on a light receiving surface of a CCD (referred to as CCD) 20. CCD20
Has an OFD voltage-sensitivity characteristic as shown in the graph of FIG. 2 and outputs a CCD driving signal.
The reflected image from the subject, which is driven by the D drive circuit 22 and is illuminated by the R, G, and B sequential illumination light, photoelectrically changes, and the image signals of the R, G, and B colors are sequentially transmitted to the video signal processing circuit 24. Output. Here, the CCD 20 receives an OFD signal from the CCD sensitivity control circuit 26 via the CCD drive circuit 22.
The sensitivity is controlled by the OFD pulse applied to the electrode. The timing pulse generator 28 applies a timing pulse to the CCD drive circuit 22 in synchronization with a synchronization signal applied from the synchronization signal
A synchronization signal is applied to the sensitivity control circuit 26. The details of the CCD sensitivity control circuit 26 will be described later.

Each color image signal output from the video signal processing circuit 24 is applied to an automatic aperture control circuit 32 and to an A / D converter 40. The automatic aperture control circuit 32 detects a video signal input from the video signal processing circuit 24, extracts luminance information from the video signal, and controls the aperture 12 so that the luminance information becomes a predetermined reference level.
Control.

The A / D converter 40 converts an input signal into a digital signal and outputs the digital signal to the field memory 42. The field memory 42 is an R memory area 42 for storing an R image signal.
The A / D converter 4 has a G memory area 42G for storing R and G image signals and a B memory area 42B for storing B image signals.
The R, G, and B color image signals sequentially added from 0 are stored in the corresponding color memory areas, and the image signals stored in these memory areas 42R, 42G, and 42B are read out at the same time. Is converted to an image signal.

On the output side of each of the memory areas 42R, 42G, 42B in the field memory 42, D
/ A converters 44R, 44G, 44B are provided,
The image signals converted simultaneously are converted into analog signals by the D / A converters 44R, 44G, and 44B, and then converted into composite video signals by the color encoder 46. Then, the composite video signal, or R,
The G and B signals are output to a monitor device (not shown), where the subject is displayed in color.

Next, the CCD sensitivity control circuit 26 will be described.
I will tell. The CCD sensitivity control circuit 26 includes a setting device
R_OFD, G_OFD, B_OFD, Switch R _SW, G_SW, B_SW,
It comprises a pulse width conversion circuit 26A and an amplification circuit 26B.
Have been. Setting device R_OFD, G_OFD, B_OFDIs the voltage
Setting volume, which is sequentially output from the CCD 20
Manifold in advance so that the image signal level for each color is constant.
Switches the voltage signal according to the_SW, G_SW, B
_SWTo the pulse width conversion circuit 26A.

Here, the switches R _SW , G _SW , and B _SW are:
B output from the enable signal generator 48,
ON / OFF is controlled by R and G enable signals B _EN , R _EN and G _EN , and turned on when the enable signals B _EN , R _EN and G _EN are input. As a result, a voltage signal is input from the setting device corresponding to the illumination light that is currently illuminating the subject. The enable signal generator 48
Are R, G, B enable signals R _EN , G _EN , B based on a detection output from a detector 49 that detects when each of the R, G, B filter areas in the color filter 13 has reached the illumination optical path. _EN , and these enable signals R _EN , G _EN , and B _EN are normally transmitted to the field memory 4.
2 are used to store image signals of colors corresponding to the respective memory areas 42R, 42G, and 42B.

That is, as shown in the timing chart of FIG.
As described above, the subject is illuminated by the R, G,
Then (FIG. 6A), one field from the CCD 20
R, G, B color image signals of the illuminated subject image with a delay
Are sequentially output (FIG. 6B). Meanwhile, the R,
G, B enable signal R_EN, G_EN, B_ENFigure 6
It occurs at the timings shown in FIGS.
As described above, the enable signal R_EN, G _EN, B_ENBy
The writing of the field memory 42 is performed. And this
Enable signal R_ENSwitch G when output_SWTurn on
And the enable signal G_ENSwitch B when output_SWOn
And the enable signal B_ENSwitch R at the output of_SWThe
Illumination light that is currently illuminating the subject
Pulse width conversion circuit 2 converts the voltage signal from the setting device corresponding to
6A.

The pulse width conversion circuit 26A outputs a pulse signal having a pulse width corresponding to the input voltage signal in synchronization with the vertical synchronizing signal. For example, the pulse signal is input from the synchronizing signal generator 30 as shown in FIG. By comparing the comparison signal A synchronized with the synchronization signal and the input voltage signal B, a pulse signal C having a pulse width corresponding to the input signal level is output to the amplifier circuit 26B.

The amplification circuit 26B has a pulse width conversion circuit 26A.
A pulse signal to be input, the reference voltage V _B is 10V as shown in FIG. 2, and amplified as peak voltage V _t becomes 15V, which in OFD electrode of CCD20 through the CCD driving circuit 22 as the OFD pulses from Apply. Thereby, the effective charge accumulation time in the CCD 20 is controlled according to the pulse width of the OFD pulse, and the sensitivity of the CCD 20 is set.

That is, as shown in FIG. 4, the total charge accumulation time (t _s + t) that can be accumulated by the CCD 20 while the illumination is on.
_{If d} ), the pulse width t _s of the OFD pulse becomes the charge release time (ineffective charge storage time), and the remaining time t _d becomes the effective charge storage time. Therefore, as described above, OFD
By making the pulse width t _s of the pulse variable corresponding to the sequential illumination light of R, G, and B, the effective charge accumulation time t _d in each of the R, G, and B fields can be controlled, respectively. As a result, R, G,
Each signal level of the B color image signal can be made constant. Note that, when observing the inside of the body cavity, the amount of reflected red light is significantly larger than the amount of reflected light of other wavelengths, then the amount of reflected green is large, and the amount of reflected blue is the smallest. Thus, the blue effective charge accumulation time is set to be the longest (the same length as the total charge accumulation time), and the effective charge accumulation time is shortened in the order of green and red.

FIG. 5 shows a second embodiment of the electronic endoscope apparatus according to the present invention.
It is a block diagram showing an example. Incidentally, the first type shown in FIG.
The same reference numerals are given to portions common to the embodiment, and the detailed description thereof will be omitted. As shown in the figure, the electronic endoscope apparatus is configured so that the pulse width of the OFD pulse can be automatically controlled in accordance with the level of the video signal for each color. That is, the CCD sensitivity control circuit 34 includes the setting devices R _OFD , G _OFD , B _OFD and the switch R _SW , of the first embodiment.
A detection circuit 34A is provided instead of G _SW and B _SW , and each output of the D / A converters 44R, 44G and 44B is applied to the detection circuit 34A via switches 47R, 47G and 47B. Here, each switch 47R, 4
7G and 47B are controlled on / off by B, R and G enable signals B _EN , R _EN and G _EN output from the enable signal generator 48, respectively, as in the first embodiment, and the enable signal B _EN , R _EN and G _EN are turned on.

Thus, a video signal of the same color as that of the illumination light which is currently illuminating the subject is input. Next, the relationship between the illumination light that currently illuminates the subject and the video signal input to the detection circuit 34A will be described with reference to the timing chart of FIG. As described above, the enable signals R _EN , G _EN , and B _{EN for} R, G, and B are set as shown in FIG.
It occurs at the timings shown in (C) to (E). Accordingly, the outputs read from the field memory 42 and converted into analog signals by the D / A converters 44R, 44G, and 44B are as shown in FIGS.

[0028] Then, to select the switch 47G when the output enable signal R _EN as described in FIG. 5, to turn on the switch 47B when the output enable signal G _EN, turn on the switch 47R when the output enable signal B _EN To capture a video signal (see FIGS. 6 (I) to 6 (K)). As a result, the video signal input to the detection circuit 34A is
As shown in (L), the color corresponds to the color of the illumination light (FIG. 6A) that currently illuminates the subject.

In the second embodiment, the video signal processing circuit 2
Although the video signal output from 4 is applied to the automatic aperture control circuit 32, it may be the same as the video signal applied to the detection circuit 34A. The detection circuit 34A
The signal to be input to the image signal is not limited to the above embodiment, and may be input, for example, via a delay unit that delays the video signal output from the video signal processing circuit 24 by two fields. Further, in the case of the second embodiment, since the same operation as the electronic shutter for controlling the charge accumulation time can be performed,
The aperture 12 and the automatic aperture control circuit 32 can be omitted.

FIG. 7 shows a third embodiment of the electronic endoscope apparatus according to the present invention.
It is a block diagram showing an example. Incidentally, the first type shown in FIG.
The same reference numerals are given to portions common to the embodiment, and the detailed description thereof will be omitted. In the third embodiment, the CCD 21 having an OFD voltage-sensitivity characteristic as shown in the graph of FIG. 8 is used, and the sensitivity of the CCD 21 is changed by increasing or decreasing the voltage of the OFD electrode.

Then, a voltage is applied to the OFD electrode of the CCD 21.
The OFD voltage is set by the setting device R_OFD, G _OFD, B_OFDFrom
Itch R_SW, G_SW, B_SWAnd via the CCD drive circuit 22
Output. In addition, switch R_SW, G_SW, B_SWIs the first
As in the embodiment, each of the enable signal generators 48
B, R, G enable signal B output_EN, R_EN, G
_ENON / OFF is controlled by the enable signal
B_EN, R_EN, G_ENTurns on when is input.

As a result, the OFD voltage from the setting device corresponding to the illumination light that is currently illuminating the subject is applied to the OFD electrode of the CCD 21, and the sensitivity of the CCD 21 is controlled for each color of the illumination light. The levels of the B color image signals are individually controlled.

[0033]

As described above, according to the electronic endoscope apparatus of the present invention, an OFD pulse having a voltage not lower than a predetermined level and having a pulse width controlled for each color of the illumination light is used as an OFD pulse.
By applying the voltage to the D electrode, the effective charge accumulation time in the solid-state imaging device can be controlled for each color of the illumination light, and the sensitivity of the solid-state imaging device can be arbitrarily adjusted for each color of the illumination light. Further, by controlling the pulse width of the OFD pulse in accordance with the color image signal level of each color of the illumination light, the luminance level of the output signal of the solid-state imaging device is constant regardless of the illumination state of the subject and the color of the illumination light. , And a mechanical aperture control mechanism can be omitted. Furthermore, O
By setting the reference voltage of the FD pulse to a relatively low value, even if the solid-state imaging device is used with high sensitivity, it is possible to prevent the image quality deterioration such as the overexposure phenomenon, so that the inside of the body cavity can be more clearly observed. In addition, there is an advantage that an illumination lamp whose illuminance decreases with time can be used longer than before.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an OFD voltage of a CCD applied to the present invention.
4 is a graph illustrating an example of a sensitivity characteristic.

FIG. 3 is a signal waveform diagram used for explaining the pulse width conversion circuit shown in FIG. 1;

FIG. 4 is a timing chart used to explain a relationship between an OFD pulse and an effective charge accumulation time.

FIG. 5 is a block diagram showing a second embodiment of the electronic endoscope apparatus according to the present invention.

FIG. 6 is a timing chart used to explain the on / off control of the switches of the first and second embodiments shown in FIGS. 1 and 5;

FIG. 7 is a block diagram showing a third embodiment of the electronic endoscope apparatus according to the present invention.

FIG. 8 is a graph showing an example of an OFD voltage-sensitivity characteristic of a CCD applied to the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Illumination lamp 13 ... Rotating color filter 20,21 ... Solid-state image sensor (CCD) 22 ... CCD drive circuit 24 ... Video signal processing circuit 26,34 ... CCD sensitivity control circuit 26A ... Pulse width conversion circuit 26B ... Amplification circuit 34A ... Detector circuit 42: Field memory 47R, 47G, 47B, R _SW , G _SW , B _SW , Switch 48: Enable signal generator R _OFD , G _OFD , B _OFD : Setting device

Claims (1)

(57) [Claims] 1. A solid-state imaging device in which R, G, and B illumination lights, which are color-separated in a time series, are radiated from a distal end portion of an endoscope to a subject, and a reflection image from the subject is disposed at the distal end portion of the endoscope. And sequentially stores the R, G, and B color image signals sequentially output from the solid-state imaging device in an image memory for each color, and simultaneously reads the R, G, and B color image signals from the image memory. An endoscope apparatus, wherein the solid-state imaging device has a sensitivity that changes according to an OFD voltage applied to an OFD electrode, wherein the sensitivity of the solid-state imaging device is set to each of R, G, and B illuminations. Setting means for setting for each light; and sensitivity control signals for R, G, and B of voltages corresponding to the respective illumination lights of R, G, and B are sequentially synchronized with the vertical synchronization signal based on the setting by the setting means. Means for outputting a signal to an OFD electrode of the solid-state imaging device. R sequentially output from the serial solid-state image pickup element, G,
An electronic endoscope apparatus wherein the level of a B color image signal is individually controlled.