JP2003069898A - Electronic scope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic scope by which an amplification factor in a signal amplifying part for generating a light control signal (YIRIS) is easily adjusted and the amplification factor with higher precision is set which is used for generating the light control signal (YIRIS) which is optimized to control diaphragm feed-back. SOLUTION: The electronic scope is provided with a solid-state imaging device and a signal processing part for outputting a luminance signal based on the output signal of the solid-state imaging device. The electronic scope is also provided with at least one variable resistance part, a deciding means for automatically deciding the resistance value of at least one variable resistance part based on the prescribed amplification factor and a light control signal generating means for generating a light control signal by amplifying the luminance signal outputted from the signal processing part by the prescribed amplification factor through the use of at least one variable resistance part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scope having a color image pickup device and a signal processing device, and an electronic endoscope system using the scope.

[0002]

2. Description of the Related Art Conventionally, an output video signal of a scope having a color image pickup device such as a color CCD (Charge Coupled Device) at the tip of an insertion portion is processed by a processor to generate a video signal, and the video signal is displayed on a CRT or the like. Electronic endoscopy systems configured to display on a device are known.

Generally, the scope is constructed so that it can be attached to and detached from the processor, and various scopes can be replaced and used according to the application.

As described above, in the electronic endoscope system, since various types of scopes are attached to the processor, it is necessary to match the signals between the scope and the processor. That is, the color video signal sent from the scope to the processor needs to be output as a signal that satisfies predetermined specifications. For this reason, the scope that employs the color CCD has a built-in signal processing device.
The output signal from the CD is subjected to predetermined processing and the standardized color video signal is output to the processor. Generally, a color video signal is a color difference signal (R-
Y, BY) and the luminance signal (Y).

Furthermore, a signal used for feedback control of a diaphragm in a light source of a processor (hereinafter referred to as a dimming signal (YIRIS)) is also output from a signal processing device of a recent electronic endoscope system. . Dimming signal (YIRIS)
Is compared in the processor with a reference value corresponding to a predetermined brightness of the preset image. The diaphragm was drive-controlled so that the dimming signal (YIRIS) coincided with the reference value.

FIG. 5 is an electric circuit diagram showing the inside of a conventional scope. As shown in FIG. 5, the signal processing device 10Z
Is a CPU 101, DSP (Digital Signal Processo)
r) 102, dimming signal generator 103Z, driver circuit 1
04, an A / D converter 105, and a buffer circuit 106. The DSP 102, under the control of the CPU 101, CC
D drive pulse is generated, and the pulse is supplied to the CCD driver 10
Send to 4. The CCD 5 repeats image pickup operations such as charge accumulation and transfer by the CCD driver 104. C
The accumulated charge transferred from CD5 is the A / D converter 105.
It is digitized by and input to the DSP 102.

The DSP 102, under the control of the CPU 101,
A luminance signal (Y) and two color difference signals (RY, BY) are generated and output to the processor. Note that R is a red component video signal, and B is a blue component video signal. here,
The luminance signal (Y) is divided into two paths. One of the divided luminance signals (Y) is directly input to the processor. The other is input to the processor via the buffer circuit 106 as a dimming signal (YIRIS) amplified by the dimming signal generation unit 103Z to an amplitude level suitable for the feedback control regarding the diaphragm.

In the above configuration, the amplification factor (gain) in the dimming signal generating section 103Z is adjusted by changing the resistance value of the trimmer resistance rZ in the initial setting at the time of shipment.
However, in the above adjusting method, the adjuster itself has to directly adjust the trimmer resistance, so that precise work and long adjusting time are required to obtain a predetermined amplification factor. Also,
In order to adjust the trimmer resistance, it is necessary to remove a part or all of the outer frame (cover) of the scope, and there is a problem that the adjuster is constantly inconvenienced.

[0009]

In view of the above circumstances, the present invention makes it possible to easily adjust the amplification factor in the signal amplifying unit for generating the dimming signal (YIRIS), and further, the feedback control of the diaphragm. Dimming signal optimized for (YIRI
It is an object to provide an electronic scope capable of setting a more accurate amplification factor for generating S) and an electronic endoscope system equipped with the electronic scope.

[0010]

In order to achieve the above object, an electronic scope according to a first aspect of the present invention includes a solid-state image pickup device and a signal processing unit for outputting a luminance signal based on an output signal of the solid-state image pickup device. Have. In addition, at least one variable resistance portion and a determination means for automatically determining the resistance value of at least one variable resistance portion based on a predetermined amplification factor,
It is characterized in that it has a dimming signal generating means for generating a dimming signal by amplifying a luminance signal output from the signal processing unit by a predetermined amplification factor using at least one variable resistor unit. That is, according to the present invention, since the brightness signal is amplified by using the variable resistance portion whose resistance value is automatically determined, the trouble of removing the outer frame of the scope to set the amplification factor is saved, and the operation is simple. The amplification factor can be set by various adjustments.

According to another aspect of the electronic scope, the dimming signal generating means has a first fixed resistance portion and a first variable resistance portion, and the determining means determines the resistance value of the first variable resistance portion. decide. In this configuration, the dimming signal is generated by resistance-dividing the luminance signal input to the dimming signal generating means by the first fixed resistance section and the first variable resistance section.

Further, by providing a buffer circuit between the signal processing section and the dimming signal generating means, a highly accurate and stable dimming signal can be output (claim 5).

According to another aspect of the electronic scope of the present invention, the dimming signal generating means is arranged between an operational amplifier to which a luminance signal is input to a non-inverting input terminal, and an output terminal and an inverting input terminal of the operational amplifier. A second fixed resistance portion provided, and a second variable resistance portion disposed between the inverting input terminal and the ground side,
The non-inverting amplifier circuit applies a voltage divided by the second fixed resistance section and the second variable resistance section to the inverting input terminal. The determining means determines the resistance value of the second variable resistance section. In this configuration, the luminance signal is passed through the non-inverting amplifier circuit to generate a desired dimming signal.

In each of the above-mentioned configurations, the first variable resistance portion and the second variable resistance portion are connected in parallel to each other in a plurality of pairs of a resistor and a switching unit for switching between a conductive state and a non-conductive state of the resistor. It is desirable that When the first variable resistance part and the second variable resistance part are configured as described above, the determining means controls the drive of each switching part in accordance with a predetermined amplification factor to thereby reduce the resistance of the first variable resistance part and the second variable resistance part. The value can be determined (claims 3 and 7).

It is preferable that the plurality of resistors forming each variable resistance portion have different resistance values (claims 4 and 8). As a result, the range of the amplification factor that can be set is expanded, and the amplification factor more suitable for the feedback control of the aperture can be set.

According to the electronic scope of the present invention,
It is preferable to use a transistor as the switching means. As a result, the determining means can make the resistance conductive by supplying the base current to the predetermined transistor.

Further, in the electronic endoscope system equipped with the above electronic scope, it is preferable that a predetermined amplification factor can be set by the processor (claim 11).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an electronic endoscope system 100 as an embodiment of the present invention.

The electronic endoscope system 100 includes a scope 7, a processor 21, and a monitor device 29. The scope 7 has an insertion part 4 formed of a flexible conduit, and a CCD 5 and a CC as a solid-state image sensor are provided at the tip of the insertion part 4.
The objective lens 6 is arranged in front of D5. Note that C
CD5 is a so-called single-plate color CCD, and a color filter is provided on the light receiving surface. An optical image of an observation target (imaging body) is formed on the light receiving surface of the color CCD 5 by the objective lens 6. Further, the light guide 1 formed of an optical fiber bundle is inserted into the scope 7. Light guide 1
One end (light emission end) of the end of the insertion part 4 (left end in the figure)
And irradiates the observation target with light via the light distribution lens 2.

The scope 7 is detachably connected to the processor 21 via the connecting portion 8. A signal processing device 10 </ b> A that performs a predetermined process on the video signal from the CCD 5 is built in near the coupling portion 8 of the scope 7. The other end of the light guide 1 reaches the inside of the processor 21 through the coupling portion 8 and is fixed at a position where the end face faces the condenser lens 11.

The lamp 13 is driven by the lamp power supply 16. The illumination light emitted from the lamp 13 is adjusted in quantity by the diaphragm mechanism 12, and the condenser lens 1
1 makes the light incident on the end face of the light guide 1. Light that has entered the light guide 1 passes through the light guide 1 and passes through the insertion portion 4
Is emitted from the end surface on the tip side of the, and is emitted toward the observation target through the irradiation lens 2.

The illumination light reflected by the observation target is imaged on the light receiving surface of the color CCD 5 by the objective lens 6. The CCD 5 transmits a color video signal corresponding to the optical image formed on the light receiving surface to the signal processing device 10. The signal processing device 10 performs various kinds of signal processing, and the processor 21
In contrast, the luminance signal (Y) and the color difference signals (RY, B-
Y) and a dimming signal (YIRIS) generated based on the luminance signal (Y) are output.

The above signals sent to the processor 21 are input to the preprocessor 22. The two color difference signals (RY, BY) and the luminance signal (Y) input to the preprocessor 22 are A / D converters 18A, 18 as they are.
After being inputted to B and 18C respectively, converted into digital signals, they are stored in the frame memory 19 in synchronization with the synchronizing signal outputted from the timing generator 17. The data stored in the memory 19 is used for freeze processing,
After being subjected to interpolation processing and the like, the D / A converters 20A, 20
Converted to analog signal at B and 20C, signal processing circuit 2
8 outputs the RGB video signal of a predetermined format to the monitor device 29. The monitor device 29 displays a color image based on the received RGB video signal.

On the other hand, the dimming signal (YIRIS) input to the preprocessor 22 is integrated by the integrator 22A,
The difference amplifier 22B is compared with the reference value Vref corresponding to the target light amount output from the system controller 27, and the shift amount of the output of the integrator 22A (that is, the brightness of the imaging target) with respect to the reference value Vref is input to the diaphragm drive circuit 22C. The aperture driving circuit 22C receives the input integrator 22A.
The diaphragm mechanism 12 is driven and controlled based on the difference between the reference value Vref and the reference value Vref. As described above, in the electronic endoscope system 100, automatic light control is performed by performing feedback control using the light control signal and the reference value Vref.

The above is the outline of the imaging operation of the electronic endoscope system 100. Hereinafter, the dimming signal (YIRIS) generation of the signal processing device 10 will be described in detail. 2 shows the scope 7
It is an electric circuit diagram which shows the 1st Example of the signal processing apparatus 10 built into. The signal processing device 10 according to the first embodiment includes a dimming signal generation unit 103A. Others, signal processing device 1
0, the same components as those of the conventional signal processing device 10Z shown in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted. In addition, a luminance signal (Y) and a color difference signal (RY, B-
The generation processing of Y) is also the same as that of the conventional signal processing device 10Z shown in FIG. 5, and therefore the description thereof is omitted here. The same applies to FIG. 3, which will be described later, regarding the second embodiment.

The dimming signal generation unit 103A includes the CPU 101.
The amplification factor is set automatically by. Therefore, the CPU 101 of the signal processing device 10 has the EEPROM 101
a is provided. The EEPROM 101a stores information on the amplification factor necessary for generating the dimming signal (YIRIS). The setting of the information regarding the amplification factor of the dimming signal generation unit 103A stored in the EEPROM 101a is executed at the time of initial setting performed at the time of shipping the electronic endoscope system 100, at the time of regular maintenance, or the like. Specifically, first, an adjuster or the like operates the front panel switch 30 of the processor 21 to set the dimming signal generation unit 103A.
At, a predetermined amplification factor is input so that a dimming signal optimized for the automatic dimming process described above is generated. Based on the input information in the front panel switch 30, the system controller 27 causes the EEPRO in the CPU 101 to operate.
Data regarding a predetermined amplification factor is written in M101a.

The dimming signal generation section 103A includes a buffer circuit bf, a first fixed resistance section Rf1, a first variable resistance section Rv1,
Have. The buffer circuit bf is provided for generating a highly accurate dimming signal. First variable resistance part Rv1
Has a total of four sets (resistor r
11 to r14, transistors TR11 to TR14) are connected in parallel. Each transistor TR1
1 to TR14 are npn type, the collector is connected to each of the resistors r11 to r14, and the base is connected to the CPU 101.

During image pickup, the CPU 101 causes the dimming signal generation unit 103A to amplify the luminance signal (Y) at a predetermined amplification factor, that is, the dimming signal (YIRIS optimized for automatic dimming in the processor 21). ) Is generated, the resistance value of the first variable resistance part Rv1 is determined. In particular,
The CPU 101 applies a current to the bases of the transistors TR11 to TR14 based on the data regarding the predetermined amplification rate written in the EEPROM 101a. CPU10
By 1, the resistance connected to the collector of the transistor to which the base current is supplied becomes conductive, and the resistance connected to the collector of the transistor to which the base current is not supplied becomes non-conductive. That is, the transistors TR11 to TR14 function as switches that switch the resistors r11 to r14 between the conductive state and the non-conductive state.
In this way, the resistance value of the first variable resistance portion Rv1 is obtained by combining the resistance values of the resistors in the conductive state among the resistors r11 to r14.

The dimming signal generation unit 103A resistance-divides the input luminance signal (Y) by the first fixed resistance unit Rf1 and the first variable resistance unit Rv1 whose resistance value is previously determined as described above. . As a result, the dimming signal (YIRIS) in a state where the luminance signal (Y) is amplified by the predetermined amplification factor is generated. The amplification factor (gain) of the dimming signal generation unit 103A is
It changes corresponding to the change in the resistance value of the first variable resistance portion Rv1. In other words, the CPU 101 determines the resistance value of the first variable resistance unit Rv1 so that a predetermined amplification factor is automatically set in the dimming signal generation unit 103A.

Table 1 shows the first fixed resistance portion Rf1 at 10K.
Ω, resistance r11 is 160 KΩ, r12 is 80 KΩ, r1
3 shows the relationship between the resistance value of the first variable resistance part Rv1 (combined resistance value of the resistors r11 to r14) and the amplification factor of the dimming signal generation part 103A when 3 is 40 KΩ and r14 is 20 KΩ.

[0031]

[Table 1]

In Table 1, "0" represents a state where no current flows through the resistor (non-conducting state), and "1" represents a state where current flows through the resistor (conducting state). The same applies to Table 2 shown later. As shown in Table 1, the first variable resistance part Rv
There are 16 types of resistance values that 1 can take. Therefore, there are 16 types of amplification factors that can be set in the dimming signal generation unit 103A.

The above is the description of the signal processing apparatus 10 of the first embodiment. As shown in Table 1, in the first embodiment, the amplification factor of the dimming signal generation unit 103A is determined within the range of 1 to about 0.5. That is, the first embodiment is suitable for the case where it is desired to generate the dimming signal (YIRIS) whose amplitude is smaller than that of the luminance signal (Y).

FIG. 3 is an electric circuit diagram showing a second embodiment of the signal processing device 10 incorporated in the scope 7. The signal processing device 10 of the second embodiment includes a dimming signal generation unit 103B. The rest of the configuration of the signal processing device 10 of the second embodiment is substantially the same as that of the first embodiment, so a description thereof will be omitted.

The dimming signal generator 103B has an operational amplifier O
P, the second fixed resistance portion Rf2, and the second variable resistance portion Rv2. The second fixed resistor section Rf2 is a feedback resistor arranged between the output terminal of the operational amplifier OP and the inverting input terminal (inverting input terminal). The second variable resistance part Rv2 is provided on the ground side. The second variable resistance part Rv2 has substantially the same configuration as the first variable resistance part Rv1 of the first embodiment. That is, a total of four sets (resistor r21
To r24, transistors TR21 to TR24) are connected in parallel. Dimming signal generator 103B
Forms a non-inverting amplifier circuit by the operational amplifier OP, the second fixed resistance part Rf2, and the first variable resistance part Rv1.

In the second embodiment, the luminance signal (Y) is input to the non-inverting input terminal (non-inverting input terminal) of the operational amplifier OP,
The luminance signal (Y) is obtained by utilizing the amplification action of the non-inverting amplifier circuit.
Is amplified at a predetermined amplification rate. The point that the amplification factor is automatically set by the CPU 101 is the same as in the first embodiment. As a result, a dimming signal (YIRIS) optimized for automatic dimming is generated. The amplification factor of the dimming signal generation unit 103B can be arbitrarily set by changing the resistance value of the second variable resistance unit Rv2 in the non-inverting amplifier circuit.

Table 2 shows that the second fixed resistance portion Rf2 is 10K.
Ω, resistance r21 is 160 KΩ, r22 is 80 KΩ, r2
3 is a table showing the resistance value of the second variable resistance part Rv2 (combined resistance value of the resistors r21 to r24) and the amplification factor of the dimming signal generation part 103B when 3 is 40 KΩ and r24 is 20 KΩ.

[0038]

[Table 2]

As shown in Table 2, there are 16 kinds of resistance values that the second variable resistance part Rv2 can take. Therefore, there are 16 types of amplification factors that can be set in the dimming signal generation unit 103B.

The above is the description of the signal processing apparatus 10 of the second embodiment. As shown in Table 2, in the second embodiment, the amplification factor of the dimming signal generation unit 103B can be determined within the range of 1 to about 2. That is, the second embodiment is suitable for the case where it is desired to generate the dimming signal (YIRIS) having a larger amplitude than the luminance signal (Y).

As described above, in the signal processing device 10, the CPU 101 automatically determines the resistance value of the first variable resistance portion Rv1 (or the second variable resistance portion Rv2) based on the preset amplification factor. To do. Also, the amplification factor can be set from the processor 21. That is, it is not necessary to remove the outer frame (cover) of the scope or directly adjust the resistor as in the conventional case, which can be convenient for the adjuster.

The above is the embodiment of the present invention. The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, the present invention can be implemented by combining the above-described first embodiment and second embodiment. FIG. 4 is an electric circuit diagram showing the dimming signal generator 103C of the third embodiment in which the above two embodiments are combined.
As shown in FIG. 4, the dimming signal generation unit 103C includes a first fixed resistance unit Rf1, a first variable resistance unit Rv1 (a part corresponding to the first embodiment), an operational amplifier OP, a second fixed resistance unit Rf2, A non-inverting amplifier circuit (corresponding to the second embodiment) including the second variable resistance portion Rv2 is provided. Therefore, the luminance signal (Y) input to the dimming signal generation unit 103C is amplified twice by resistance division of the non-inverting amplifier circuit and the first fixed resistance unit Rf1 and the first variable resistance unit Rv1. .

According to the third embodiment, compared to the other embodiments,
Although the scale of the dimming signal generation unit 103C, that is, the signal processing device 10 itself becomes large, the amplification factor can be set more accurately accordingly. That is, it is possible to generate a dimming signal (YIRIS) suitable for automatic dimming in the processor 21.

In the above-described embodiment, the color CCD 5 is used as the image pickup device arranged at the tip of the scope 7, but the present invention is not limited to this, and a monochrome CCD may be used. If a monochrome CCD is used to capture a color image, the RGB rotary filter may be arranged at a position where the light emitted from the lamp 13 is incident.

Each variable resistance portion Rv described in each of the above embodiments.
1 and Rv2 are merely examples. Therefore, the number of resistances (and transistors) forming the variable resistance portion and the resistance value thereof can be arbitrarily determined in consideration of the size of the signal generation device 10 and the accuracy of amplification factor setting. Is. For example, in the third embodiment shown in FIG.
It is also possible to configure either one of the variable resistance units Rv1 and Rv2 with only one set of resistance and transistor.

In the above embodiment, the signal generator 10 is used.
The amplification factor is set using the processor 21.
However, the electronic scope of the present invention can set the amplification factor of the signal generation device 10 other than the processor 21. For example, it can be set by electrically connecting an electronic scope to a device dedicated to setting the amplification factor. This is effective when it is necessary to set a large number of electronic scopes at once, such as at the time of initial setting.

[0048]

As described above, according to the electronic scope of the present invention, the resistance value of the variable resistance portion is automatically set in the signal generator based on the predetermined amplification factor inputted from the outside. It is not necessary to remove the outer frame of the electronic scope or adjust the variable resistance portion by the operator himself, and the amplification factor for generating the dimming signal can be easily set.

Further, according to the present invention, the variable resistance section is formed by connecting a plurality of resistances in parallel, and the resistance value of the entire variable resistance section is determined by the conductive state of the plurality of resistances. A more accurate resistance value corresponding to a predetermined amplification factor can be determined in a shorter time than by directly adjusting the variable resistance portion. That is, the electronic scope of the present invention can generate a dimming signal optimized for automatic dimming from the luminance signal.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an electronic endoscope system according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a signal generator of the first embodiment.

FIG. 3 is an electric circuit diagram showing a signal generation device of a second embodiment.

FIG. 4 is an electric circuit diagram showing a dimming signal generator in the signal generator of the third embodiment.

FIG. 5 is an electric circuit diagram showing a conventional signal generator.

[Explanation of symbols]

7 scope 10 Signal processing device 101 CPU 103A, 103B dimming signal generator Rf1, Rf2 fixed resistance part Rv1, Rv2 variable resistance part OP operational amplifier 21 processors 100 electronic endoscope system

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H040 BA09 CA04 CA10 CA11 DA03                       GA02 GA05 GA11                 4C061 AA00 BB00 CC06 DD00 LL02                       MM02 MM07 NN01 NN05 QQ09                       RR02 RR15 RR22 RR30 TT01                 5C022 AA09 AB03 AB12 AC42 AC54                       AC55 AC69

Claims (11)

[Claims] 1. A solid-state image sensor, a signal processing unit for outputting a luminance signal based on an output signal of the solid-state image sensor, at least one variable resistor unit, and the at least one variable resistor based on a predetermined amplification factor. And a deciding means for automatically deciding the resistance value of the unit, and dimming by amplifying the luminance signal output from the signal processing unit by the predetermined amplification factor using the at least one variable resistance unit. A dimming signal generating means for generating a signal, and an electronic scope. 2. The electronic scope according to claim 1, wherein the dimming signal generating means includes a first fixed resistance section and a first variable resistance section, and the determining means is the first variable resistance section. The dimming signal is generated by determining the resistance value of the dimming signal and dividing the luminance signal to be input to the dimming signal generating means by the first fixed resistance section and the first variable resistance section. An electronic scope characterized by. 3. The electronic scope according to claim 2, wherein the first variable resistance section includes a plurality of resistances and a switching section for switching between a conductive state and a non-conductive state of the resistances connected in parallel. The determining means determines the resistance value of the first variable resistance section by drivingly controlling the switching section of the first variable resistance section according to a predetermined amplification factor. . 4. The electronic scope according to claim 3, wherein the plurality of resistors of the first variable resistance section have different resistance values from each other. 5. The electronic scope according to claim 1, further comprising a buffer circuit between the signal processing unit and the dimming signal generation means. . 6. The electronic scope according to claim 1, wherein the dimming signal generating means includes an operational amplifier that inputs the luminance signal to a non-inverting input terminal, and an output terminal of the operational amplifier. A second fixed resistance portion disposed between the inverting input end and a second variable resistance portion disposed between the inverting input end and the ground side. A variable resistance section and a non-inverting amplifier circuit for applying a voltage resistance-divided to the inverting input terminal, the determining means determines the resistance value of the second variable resistance section, the luminance signal is the An electronic scope, wherein the dimming signal is generated through a non-inverting amplifier circuit. 7. The electronic scope according to claim 6, wherein the second variable resistance section includes a plurality of resistances and a switching section for switching between a conductive state and a non-conductive state of the resistances connected in parallel. The determination means determines the resistance value of the second variable resistance section by drivingly controlling the switching section of the second variable resistance section according to a predetermined amplification factor. . 8. The electronic scope according to claim 7, wherein the plurality of resistors of the second variable resistance portion have different resistance values. 9. The electronic scope according to claim 3, wherein each switching unit is a transistor, and the determining unit applies a base current to a predetermined transistor according to a predetermined amplification factor. An electronic scope characterized in that the transistor is driven and controlled by flowing. 10. An electronic endoscope system comprising: the electronic scope according to any one of claims 1 to 9; and setting means for arbitrarily setting a predetermined amplification factor. 11. The electronic endoscope system according to claim 10, wherein the setting unit includes a dimming unit that dims light that illuminates an observation target from the electronic scope using the dimming signal. An electronic endoscope system characterized by: