JPH05252450A - Electronic endoscope device - Google Patents

Abstract

PURPOSE:To vary sensitivity of a solid-state image pickup element, to brightly photograph a dark part which cannot be corrected entirely by light quantity control executed by a conventional diaphragm, and also, to use an illuminating lamp longer than conventional by controlling an OFD voltage applied to an OFD electrode of the solid-state image pickup element in accordance with an output signal of the solid-state image pickup element. CONSTITUTION:An object to be photographed is irradiated with an illuminating light from the tip part of the endoscope, a reflected image from the object to be photographed concerned is photodetected by a solid-state image pickup element 20 provided in the tip part of the endoscope, and an output signal of the solid-state image pickup element 20 is processed and outputted to a monitor TV. The solid-state image pickup element 20 generates a sensitivity control signal of a voltage corresponding to an output signal level of the solid- state image pickup element 20, in the electronic endoscope device in which the sensitivity is varied in accordance with an OFD voltage applied to an OFD electrode, and this device is provided with a CCD sensitivity control circuit 26 for outputting this generated sensitivity control signal to the OFD electrode of the solid-state image pickup element 20 as the OFD voltage.

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 picking up an image of a subject under irradiation of illumination light.

[0002]

2. Description of the Related Art An electronic endoscope used for medical or industrial purposes comprises an endoscope body, a processor, and a monitor device, and an insertion portion of the endoscope body is inserted into a body cavity or the like. , Illuminating light toward a subject from an illumination device built in or independent of the processor, photoelectrically converting a reflected image from the subject by a solid-state imaging device such as CCD, and transmitting the photoelectrically converted signal to the processor, The processor performs signal processing and then displays in color on the monitor device.

Here, in order to reduce the diameter of the insertion portion of the endoscope main body, normally, one solid-state image pickup device is used to obtain a color image signal. There are a so-called simultaneous system and a frame-sequential system as a system for obtaining this color video signal. In the simultaneous method, a color filter array that passes red (R), green (G), and blue (B) wavelength light is arranged in a checkered pattern on the light receiving portion of the solid-state image sensor, and the solid-state image sensor is exposed. Then, the R, G, and B accumulated charges accumulated in each pixel of the light receiving section are read out, and then signal processing is performed to create a color image signal. Illumination by R, G, and B color region lights is sequentially repeated through the rotating color filter, while the solid-state imaging device repeats charge accumulation and transfer for each color illumination, thereby Each color image signal is formed for each field, and these color image signals are converted into R,
This is a method of creating a color video signal by converting it into a simultaneous signal through the G and B field memories.

[0004]

In order to obtain a clear and high-quality image when driving a solid-state image pickup device to capture an image of a subject, regardless of the simultaneous method or the frame-sequential method, it is necessary to Must be illuminated with an appropriate amount of illumination light. However, the appropriate amount of illumination light is not constant depending on the positional relationship between the tip of the insertion portion of the endoscope main body provided with the illumination window and the observation window and the subject, 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 the amount of light received by the solid-state image sensor also 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 image sensor is too large and the solid-state image sensor is saturated immediately, causing a so-called white crushing phenomenon, and detailed information of the white portion of the monitor image. Is missing, and the image quality deteriorates.

Therefore, conventionally, there is provided a mechanism for adjusting the amount of illumination light emitted from the illumination lamp according to the position of the subject, the reflectance of the light of the subject, and the like, which changes the amount of light reflected from the subject. The change in the amount of light received by the solid-state image sensor is adjusted accordingly. The mechanism for adjusting the amount of illumination light is composed of a diaphragm for mechanically controlling the illumination light, a diaphragm drive mechanism for driving the diaphragm, and a control circuit for controlling the diaphragm drive mechanism. The control circuit is a solid-state image sensor. The output signal of is detected and the brightness information in it is taken out, and the diaphragm drive mechanism is controlled so that this brightness information becomes a predetermined reference level, which allows illumination so that the output level of the solid-state image sensor becomes almost constant. The light intensity is adjusted.

By the way, it is known that illumination lamps such as xenon lamps decrease in light amount with time.
When the amount of light decreases, the screen becomes dark even if the diaphragm is opened. Therefore, there has been a potential demand for using an expensive lamp for a long time and observing the affected area clearly, but the lamp must be replaced every 200 hours or so.

The present invention has been made in view of the above circumstances, and it is possible to capture a bright image of a dark place that cannot be corrected by the conventional light amount control using the diaphragm, and to use the illumination lamp longer than before. It is an object of the present invention to provide an electronic endoscope device capable of performing the above.

[0008]

In order to achieve the above-mentioned object, the present invention irradiates a subject with illumination light from the tip of the endoscope and arranges a reflected image from the subject on the tip of the endoscope. An electronic endoscopic device that receives light by a solid-state image sensor, processes an output signal of the solid-state image sensor, and outputs the signal to a monitor TV, wherein the solid-state image sensor is an OFD applied to an OFD electrode.
In an electronic endoscope device whose sensitivity changes according to the voltage,
It is characterized by further comprising: means for generating a sensitivity control signal having a voltage corresponding to an output signal level of the solid-state image sensor, and means for outputting the generated sensitivity control signal to an OFD electrode of the solid-state image sensor. There is.

[0009]

The present invention focuses on the fact that the sensitivity of the solid-state image sensor changes depending on the OFD voltage applied to the overflow / drain (hereinafter referred to as OFD) electrode of the solid-state image sensor. The fixed OFD voltage is changed according to the output signal level of the solid-state image sensor, so that under low illumination or when the amount of light reflected from the subject is small (that is, when the amount of light incident on the solid-state image sensor is small). ), High-sensitivity images can be obtained, and blooming does not occur even when the amount of light incident on the solid-state image sensor increases.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of an electronic endoscope apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. First, the present invention will be described in principle. Some solid-state imaging devices have an OFD electrode. In this OFD electrode, the charge accumulated in the light receiving portion of the solid-state imaging device by incident light within the charge accumulation time is usually defined by the potential of the OFD electrode. When a certain amount of charge is reached, excess charge is discharged to the drain as excess charge and is provided to reduce blooming when the amount of incident light is large. As shown in FIG. 2, the sensitivity of the solid-state imaging device may change depending on the increase / decrease in the voltage of the OFD electrode.

Using such a solid-state image sensor,
By controlling the OFD voltage applied to the FD electrode according to the output signal of the solid-state image sensor, the sensitivity of the solid-state image sensor is controlled according to the illumination state of the object. By reducing the sensitivity, it reduces the darkness of the image and enables a clearer observation of the affected area in the body cavity.

FIG. 1 shows a first electronic endoscope apparatus according to the present invention.
It is a block diagram which shows an Example, and has shown about the simultaneous system. In the figure, 10 is an illumination lamp that emits white light (for example, a xenon lamp), and 14 is a light guide. Illumination light emitted from the illumination lamp 10 is passed through the condenser lens 11 and the diaphragm 12 to the light guide 1
4 is incident on the light incident end 14A, transmitted by the light guide 14, and emitted from the light exit end 14B toward the subject through the illumination lens 16.

The reflected image from the object illuminated in this way is passed through the objective lens 18 and a solid-state image sensor (hereinafter
An image is formed on the light receiving surface of a CCD 20. CCD 20
Is a CC that has an OFD voltage-sensitivity characteristic as shown in the graph of FIG. 2 and that outputs a CCD drive signal.
It is driven by the D drive circuit 22 and outputs R, G, and B color image signals to the video signal processing circuit 24, and the CCD
From the sensitivity control circuit 26 through the CCD drive circuit 22 to OF
The sensitivity is controlled by the OFD voltage (sensitivity control signal) applied to the D electrode. The timing pulse generator 28
Applies a timing pulse to the CCD drive circuit 22 and a clamp pulse to the CCD sensitivity control circuit 26 in synchronism with the synchronization signal applied from the synchronization signal generator 30. The details of the CCD sensitivity control circuit 26 will be described later.

The video signal processing circuit 24 arithmetically combines the color image signals input from the CCD 20, outputs the color video signal to a monitor device (not shown), and outputs it to the CCD sensitivity control circuit 26 and the automatic aperture control circuit 32. The automatic aperture control circuit 32 detects the video signal input from the video signal processing circuit 24 and extracts the luminance information therein,
The diaphragm 12 is controlled so that the brightness information becomes a predetermined reference level set in advance.

Next, the CCD sensitivity control circuit 26 will be described. FIG. 3 is a circuit diagram showing a concrete example of the CCD sensitivity control circuit 26. The CCD sensitivity control circuit 26 mainly includes an amplifier circuit 26A, a clamp circuit 26B, an OFD reference voltage setting circuit 26C, an emitter follower 26D and the like. The video signal input from the video signal processing circuit 24 is
After being amplified to a predetermined level by the amplifier circuit 26A, it is added to the clamp circuit 26B. Clamp circuit 2
A clamp pulse is applied to the 6B from the timing pulse generator 28, and the OFD reference voltage setting circuit 2
The OFD reference voltage is set by 6C. Incidentally, O
The FD reference voltage setting circuit 26C is set to O by the variable resistance VR.
The FD reference voltage can be set appropriately.

The clamp circuit 26B turns on the transistor Tr each time a clamp pulse synchronized with the synchronizing signal is applied, and the video signal amplified to a predetermined level is forced to O.
It is clamped to the FD reference voltage (for example, 5V) and is output as a sensitivity control signal via the emitter follower 26D. Although this sensitivity control signal has a waveform corresponding to the input video signal, it may be integrated in the CCD sensitivity control circuit 26.

The sensitivity control signal generated by the CCD sensitivity control circuit 26 in this way is transferred to the CCD drive circuit 22.
Is applied to the OFD electrode of the CCD 20 via the
Control the sensitivity of zero. That is, as shown in the graph of FIG. 2, the sensitivity of the CCD 20 changes depending on the OFD voltage. Therefore, when the video signal is large, the sensitivity control signal (OFD voltage) becomes large and the CCD sensitivity is lowered.
The output level also decreases, while the OFD voltage decreases when the video signal is small, increasing the CCD sensitivity, which increases the CCD output level.

FIG. 4 shows a second electronic endoscope apparatus according to the present invention.
It is a block diagram which shows an Example. Incidentally, the first shown in FIG.
The same parts as those of the embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG.
It differs from the first embodiment in that a switch 34 and a video level detection circuit 36 are added as compared with the first embodiment. That is, the video level detection circuit 36 detects whether or not the video signal applied from the video signal processing circuit 24 is at a certain level or higher.
CCD signal control circuit 2 to turn on the video signal from off to on
Output to 6.

As a result, the CCD 20 is used with high sensitivity when the video signal is below a certain level, and the OFD voltage is raised when the video signal is above a certain level.
The CCD sensitivity is lowered to suppress blooming. FIG. 5 shows a third example of the electronic endoscope apparatus according to the present invention.
It is a block diagram which shows an Example, and has shown about the frame sequential method. The same parts as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in the figure, the electronic endoscope apparatus of the third embodiment is of a frame-sequential type and has an aperture 12 and a light guide 1.
4 between the four incident ends 14A and the rotating color filter 13
Is installed. This color filter 13 has R
R filter region that transmits light in the red wavelength region, and G
G filter region that transmits light in the (green) wavelength region, and B
A B filter region for transmitting light in the (blue) wavelength region is provided, and by rotating this color filter 13, sequential illumination is performed with R, G, and B wavelength lights. This R, G, B sequential illumination light is emitted from the light guide 14.
And is emitted from the exit end 14B toward the subject through the illumination lens 16. CCD 20
Photoelectrically converts a reflected image from a subject illuminated by the R, G, B sequential illumination light, and sequentially outputs image signals of R, G, B colors to the video signal processing circuit 24. Each color image signal output from the video signal processing circuit 24 is added to the CCD sensitivity control circuit 26 and the automatic aperture control circuit 32 as in the first embodiment, and also to the A / D converter 40.

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

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

FIG. 6 shows a fourth example of the electronic endoscope apparatus according to the present invention.
It is a block diagram which shows an Example. The third shown in FIG.
The same parts as those of the embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in the figure, in the fourth embodiment,
The video signal input to the CCD sensitivity control circuit 26 is different from that of the third embodiment.

That is, the D / A converters 44R, 44G, 44
Each output of B is applied to the CCD sensitivity control circuit 26 via the switches 47R, 47G and 47B. Here, on / off of each of the switches 47R, 47G, 47B is controlled by the enable signals B _EN , R _EN , G _{EN of} B, R, G output from the enable signal generator 48,
It is turned on when the enable signals B _EN , R _EN , and G _EN are input.

As a result, a video signal of the same color as the color of the illumination light currently illuminating the subject is input. The enable signal generator 48 outputs the R, G, B enable signals based on the detection output from the detector 49 that detects when the R, G, B filter regions of the color filter 13 face the illumination optical path. Generating R _EN , G _EN , and B _EN , these enable signals R _EN , G _EN , and B _EN
Is usually a memory area 42R of the field memory 42,
It is used to store image signals of colors corresponding to 42G and 42B.

Next, the relationship between the illumination light currently illuminating the subject and the video signal input to the CCD sensitivity control circuit 26 will be described with reference to the timing chart of FIG. As shown in FIG. 7A, when a subject is illuminated by sequential illumination light of R, G, B, the R, G, B color image signals of the illuminated subject image are delayed by one field from the CCD 20. The signals are sequentially output (FIG. 7 (B)).

On the other hand, R, G, B enable signals R _EN ,
G _EN and B _EN are generated at the timings shown in FIGS. 7C to _7E , and the enable signals R _EN and G _EN are generated as described above.
_The field memory 42 is written by _EN and B _EN . Therefore, D read from the field memory 42
The outputs converted into analog signals by the / A converters 44R, 44G, and 44B are as shown in FIGS. 7 (F) to (H).

Then, as described with reference to FIG. 6, the switch 47G is turned on when the enable signal R _EN is output, the switch 47B is turned on when the enable signal G _EN is output, and the switch 47R is turned on when the enable signal B _EN is output. To capture the video signal (see FIGS. 7 (I) to 7 (K)). As a result, the video signal input to the CCD sensitivity control circuit 26 becomes as shown in FIG. 7L, which corresponds to the color of the illumination light (FIG. 7A) currently illuminating the subject.

In the fourth embodiment, the video signal processing circuit 2
Although the video signal output from No. 4 is applied to the automatic aperture control circuit 32, it may be the same signal as the video signal applied to the CCD sensitivity control circuit 26. Also, CCD
The signal input to the sensitivity control circuit 26 is not limited to that in the above embodiment, but may be input via a delay unit that delays the video signal output from the video signal processing circuit 24 by two fields.

[0030]

As described above, according to the electronic endoscope apparatus of the present invention, the OFD voltage is changed in accordance with the output signal level of the solid-state image pickup device, so that the conventional light amount control by the diaphragm is not performed. It has the advantages of being able to image a dark area that cannot be corrected brightly, allowing more clear observation of the inside of the body cavity, and being able to use an illumination lamp whose illuminance decreases over time longer than before. ..

[Brief description of drawings]

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

FIG. 2 shows the OFD voltage of CCD applied to the present invention.
It is a graph which shows an example of a sensitivity characteristic.

FIG. 3 is a circuit diagram showing a specific example of the CCD sensitivity control circuit shown in FIG.

FIG. 4 is a block diagram showing a second embodiment of the electronic endoscope apparatus according to the present invention.

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

FIG. 6 is a block diagram showing a fourth embodiment of the electronic endoscope apparatus according to the present invention.

FIG. 7 is a timing chart used to explain the fourth embodiment shown in FIG.

[Explanation of symbols]

 10 ... Illumination lamp 13 ... Rotating color filter 20 ... Solid-state image sensor (CCD) 22 ... CCD drive circuit 24 ... Video signal processing circuit 26 ... CCD sensitivity control circuit 28 ... Timing pulse generator 34, 47R, 47G, 47B ... Switch 36 ... video level detection circuit 42 ... field memory 48 ... enable signal generator

Claims (3)

[Claims] 1. A subject is irradiated with illumination light from the tip of an endoscope, and a reflected image from the subject is received by a solid-state image sensor provided at the tip of the endoscope, and an output signal of the solid-state image sensor is output. An electronic endoscope apparatus for signal processing and outputting to a monitor TV, wherein the solid-state imaging device is an OFD applied to an OFD electrode.
In the electronic endoscope apparatus in which the sensitivity changes according to the voltage, means for generating a sensitivity control signal having a voltage corresponding to the output signal level of the solid-state image sensor, and the generated sensitivity control signal of the solid-state image sensor. OF
An electronic endoscope apparatus comprising: a means for outputting to a D electrode. 2. A subject is irradiated with illumination light from the tip of the endoscope, and a reflected image from the subject is received by a solid-state image sensor provided at the tip of the endoscope, and an output signal of the solid-state image sensor is output. An electronic endoscope apparatus for signal processing and outputting to a monitor TV, wherein the solid-state imaging device is an OFD applied to an OFD electrode.
In an electronic endoscope apparatus in which the sensitivity changes according to a voltage, when the output signal level of the solid-state image sensor is equal to or higher than a reference level, a unit that generates a sensitivity control signal having a voltage corresponding to the output signal level, If the output signal level is below the reference level,
A predetermined OFD voltage for increasing the sensitivity is output to the OFD electrode of the solid-state image sensor, and when the output signal level is equal to or higher than the reference level, the generated sensitivity control signal is output to the OFD electrode of the solid-state image sensor. An electronic endoscope apparatus comprising: a means for outputting. 3. A solid-state image sensor in which R, G, and B illumination lights, which are color-separated in time series, are applied to a subject from a tip portion of the endoscope, and a reflected image from the subject is arranged at the tip portion of the endoscope. An electronic device for receiving the color image signals of R, G, B sequentially output from the solid-state image sensor in the image memory for each color and reading the color image signals of R, G, B simultaneously from the image memory. In the endoscope apparatus, the solid-state imaging device has a sensitivity that changes according to an OFD voltage applied to an OFD electrode. Means for taking out a color image signal of the same color as the above, a means for producing a sensitivity control signal having a voltage corresponding to the signal level of the taken out color image signal, and the produced sensitivity control signal for the OF of the solid-state imaging device.
An electronic endoscope apparatus comprising: a means for outputting to a D electrode.