DE10036448A1 - Electronic endoscope image element has rectangular image area with strip-shaped shadow areas of essentially same width on two opposing sides for detecting reference black level - Google Patents

Abstract

The endoscope image element has an essentially rectangular image area (521) with a strip-shaped shadow area (522,523) on two opposing sides for detecting a reference black level, whereby both shadow areas are essentially of the same width. The two sides of the image area are arranged on both ends of the image element relative to a horizontal scan direction in the image element. An Independent claim is also included for an electronic endoscope.

Description

The invention relates to a picture element for electronic endoscopes and an elek tronic endoscope equipped with such a picture element.

In the field of medicine, electronic endoscope systems come as diagnostics systems used to internal parts of the human body like that Examine esophagus.

Such electronic endoscope systems usually contain a light source lenvorrichtung and an endoscope detachably on the light source device mon is. The endoscope has a CCD image sensor as an image element and an opti imaging system at its top.

Fig. 8 shows a particular electronic endoscopes CCD image sensor 100 according to the prior art. As shown in FIG. 8, the known CCD image sensor 100 includes a rectangular case 110 .

Inside the housing 110 there is a CCD chip 120 which contains a rectangular image area 131 . Along the short sides 140 of the image area 131 , ie along the sides perpendicular to the horizontal scanning direction shown in FIG. 8, a plurality of connections 150 of the CCD chip 120 are arranged.

On the bottom surface of the housing 110 , a plurality of pins, not shown in FIG. 8, are also connected. These pins are cut with corresponding Kontaktab or web sections 180 electrically connected. About these Kontaktab sections 180 and 170 via wires, the pins are electrically connected to the corresponding terminals 150 .

One of the short sides 140 of the image area 131 of the CCD image sensor 100 is provided with a band-shaped shadow area 132 , which is used to detect a reference level for "optically black" and is shown in FIG. 8 by the oblique lines. The shadow area 132 is commonly referred to as a "black area".

Usually, the CCD image sensor 100 is designed such that the center 111 of the housing 110 is aligned with the center 133 of the image region 131 , ie coincides therewith. On the other hand, the image area 131 of the CCD image sensor 100 consists of the shadow area 132 and an effective area 135 , which forms a different section of the image area 131 than the shadow area 132 . As a result, the center 134 of the effective area 135 of the image area 131 is not aligned with the center 111 of the housing 110 .

The CCD image sensor 100 and the optical imaging system are provided inside a predetermined opening formed in the tip of the electronic endoscope. However, as explained above, the center 134 of the effective area 135 is offset from the center 111 of the housing 110 . If the CCD image sensor 100 is mounted in the opening without any adjustment, the center of the optical imaging system is therefore not aligned with the center 134 of the effective area 135 . The center of the imaging optical system is given by the intersection of the optical axis of the imaging system and the light receiving surface 130 .

For this reason, a centering adjustment, ie a adjustment to correct the eccentricity, is carried out when the CCD image sensor 100 is inserted into such an opening when the electronic endoscope is being assembled.

Such centering adjustment is performed by attaching a spacer (centering means) 190 to the outside of the housing 110 using a suitable tensioner so that the center 191 of the image sensor 100 containing the spacer 190 is at the center 134 of the effective area 135 is aligned. In practice, an insulating tape is used as a spacer. The centering / adjustment is then performed so that the insulating tape is wound around the housing 110 , so that the space around the housing 110 is filled with the wrapped insulating tape.

Such centering / adjustment is difficult to perform automatically The assembly of electronic endoscopes therefore requires considerable effort time and effort.

Since the spacer 190 must be adjusted on the outside of the CCD image sensor 100 , additional space is required inside the tip of the electronic endoscope in which the spacer 190 can be accommodated. As a result, there arises a problem that the diameter of the endoscope must be enlarged accordingly.

The object of the invention is to provide a picture element for an electronic endoscope and to specify an endoscope equipped with such a picture element, which allow the picture element to be positioned easily and reliably and the diameter of the endoscope can be reduced.  

The invention solves this problem by the picture element with the features of Claim 1 or by the electronic endoscope with the features of the An Proverbs 5

Since the invention enables a centering means such as one of the adjustment to do without the spacer on the outside of the picture element Reduced diameter of the electronic endoscope and also the Reduced the number of steps required to assemble the endoscope become.

The electronic endoscope according to the invention as a medical endo skop used, so by reducing the endoscope diameter load on the patient can be reduced.

Since none of the center when assembling the endoscope according to the invention tion, d. H. adjustment used to correct the eccentricity assembly must be compared to the case in which one such adjustment is required, easily and quickly.

Advantageous developments of the invention are the subject of the dependent claims and the following description.

The invention is explained in more detail below with reference to the figures. In it gene:

Fig. 1 is a block diagram of an embodiment of an electronic endoscope according to the invention and a light source apparatus to which the endoscope is connected,

Fig. 2 is a block diagram of a signal-Vorverarbeitungsprozessors of the electronic endoscope shown in FIG. 1,

Fig. 3 is a block diagram of a signal processing circuit of the light source device of Fig. 1,

Fig. 4, the tip of the electronic endoscope shown in FIG. 1 in bottom and cross-sectional view,

Fig. 5 shows an embodiment of a CCD image sensor of the invention in top and side view,

Fig. 6 is a diagram showing the timing of the generation Klammersignal-,

Fig. 7 is a timing diagram showing the timing of the clip processing, and

Fig. 8 is a plan view of an electronic endoscopes certain CCD image sensor according to the prior art.

Fig. 1 shows a block diagram of a preferred embodiment of the electronic endoscope according to the invention and the construction of a light source device which is connected to the electronic endoscope. Fig. 2 shows in a block diagram the structure of a signal preprocessing processor of the electronic endoscope of Fig. 1. Fig. 3 also shows in a block diagram the structure of a signal processing circuit of the light source device shown in Fig. 1. Fig. 4 shows the tip of the endoscope shown in Fig. 1 in a bottom and a cross-sectional view. The optical imaging system is not shown in the bottom view according to FIG. 4.

As shown in FIG. 1, an electronic endoscope system 300 includes a light source device 8 and an electronic endoscope 1 , which is detachably connected to the light source device 8 .

The endoscope 1 is permitted with a long, flexible (elastic) main body 2 .

The main body 2 has an operating part 23 at its base end. Inside the main body 2 , several functional channels run in its longitudinal direction. As shown in Fig. 4, there are an instrument channel 41 through which forceps and treatment instruments such as medical laser instruments are passed, a water supply channel 42 , an air supply channel 43 and two channels for holding optical fiber bundles 44 and 45 , hereinafter briefly referred to as light waves to be called head.

As shown in Fig. 4, two lighting lenses 31 and 32 are provided in the tip of the main body 2 . The illumination lenses 31 and 32 are scattering lenses and are provided at the tip of the respective optical waveguide 44 and 45 , respectively.

In the main body 2 an opening 46 is formed along its longitudinal direction. As shown in FIG. 4, the opening 46 is arranged eccentrically from the central axis 22 of the main body 2 .

Inside the opening 46 in the tip 21 of the main body 2 there are an optical imaging system which contains an objective lens 33 , a convex lens 34 , a concave lens 35 , a convex lens 36 and an optical low-pass filter 37 , and a CCD image sensor 5 as a picture element. The components just mentioned are arranged in this order from the tip, ie from the left in FIG. 4, to the base, ie to the right in FIG. 4.

The CCD image sensor 5 is held on a frame element 61 . Both the CCD image sensor 5 and the frame element 61 are inserted into the opening 46 . The frame element 61 has a cylindrical shape and a cavity in its center which is square in cross section.

The convex lenses 34 and 36 and the concave lens 35 are held on a lens holder 62 and used together with this in the opening 46 . The lens holder 62 has a cylindrical shape and a cavity in the middle. Between the convex lens 34 and the concave lens 35 , a spacer ring 38 is arranged.

The objective lens 33 is arranged in the central region of the opening 46 at the tip of the main body 2 , ie on the side of the opening 46 facing the tip.

The optical axes of the convex lenses 34 , 36 and the concave lens 35 held on the lens holder 62 are all aligned with the central axis of the lens holder 62 . The optical axis of the objective lens 33 is aligned with the central axis of the lens holder 62 when the latter is inserted into the interior of the opening 46 . The endoscope 1 is thus designed such that the optical axes of the objective lens 33 , the convex lenses 34 , 36 and the konka ven lens 35 are all aligned with one another, that is, they agree with one another.

If the CCD image sensor 5 is in a state in which it is held in the frame element 61 , the center 591 of the image region 521 , ie the center 592 of an effective region 524 explained later, is in one on the center axis of the frame element 61 Light receiving surface 52 of the CCD image sensor 5 aligned.

If the frame element 21 and the lens holder 22 are in a state in which they are inserted into the interior of the opening 46 , the central axis of the frame element 61 is aligned with the central axis of the lens holder 62 , and the optical axis O of the optical imaging system runs through the center 592 of the effective area 524 formed on the light receiving surface 52 of the CCD image sensor 5 .

The optical low-pass filter 37 is located at a central portion of a cover from 50 a of the CCD image sensor 5 , which will be described later.

FIG. 5 shows a preferred embodiment of the CCD image sensor 5 serving as a picture element in a top view and a side view.

As shown in Fig. 5, the CCD image sensor 5 has a housing 50 which has the shape of a right-angled parallelepiped. The housing 50 has a base part 50 b and the transparent cover 50 a, which is brought to the base part 50 b.

A CCD chip 51 is accommodated in the interior of the housing 50 and contains a right-angled image area 221 .

The CCD chip 51 is equipped with a plurality of connections 55 . For the sake of simplicity of illustration, the CCD image sensor 5 in FIG. 5 has six connections 55 (pins 56 ).

Three of the connections 55 are arranged along the long side 54 a, that is, along a line running parallel to the horizontal scanning direction according to FIG. 5, while the other three connections 55 lie along the other, opposite the long side 54 b and thus in turn parallel to horizontal scanning direction extending line are arranged.

In this way, the connections 55 are arranged along the long sides 54 a and 54 b of the image area 521 . They are thus arranged along lines that run perpendicular to the shadow areas 522 and 523 . Are arranged in comparison to the case in which the terminals 55 along the short sides 53a, 53b of the Bildbe realm 521, so the length of the SES in the front surface of Gehäu 50 extending diagonal line and the length of the longitudinal sides of the front surface of the housing 50 can be shortened become. The front surface of the housing 50 is the surface on the side on which the light receiving surface 52 is located. It is thus possible to reduce the diameter of the opening 46 and thus the diameter of the main body 2 .

At the base portion 50 b at locations near the terminals 55 , corre sponding contact portions or web portions 58 are provided, each of which is electrically connected to the corresponding terminal 55 via a lead wire 57 .

Six L-shaped pins 56 are connected to the bottom surface of the base section 50 b of the housing 50 . Three of these pins 56 are arranged in a row along the long side 54 a of the image area 521 , while the remaining three pins 56 are arranged in a row along the other long side 54 b.

The pins 56 are each connected at one end to the corresponding Kontaktab section 58 electrically connected. About the contact portions 58 and the Lei wires 57 so the pins 56 are electrically connected to their corresponding terminals 55 of the CCD chip 51 .

On both short sides 53a, 53b of the image area 521 of the CCD image sensor 5 , that is to say the sides which are at the two end sections in the direction of view of the horizontal scanning direction shown in FIG. 5, band-shaped shadow areas 522 and 523 are provided, which facilitate the detection serve a reference level for "optically black" and are shown in Fig. 5 by the oblique lines. The shadow areas 522 and 523 are commonly referred to as "black areas".

The following applies to the dimensions of the shadow areas 522 and 523 :
The shadow area 522 has a width a that is constant in the direction of a line parallel to the short side 53a. The shadow area 523 has a width b that is constant in the direction of a line parallel to the short side 53b. Furthermore, the widths a and b are dimensioned so that they are equal to one another. In this way, the center of that area of the image area 521 from which the shadow areas 522 and 523 are excluded, ie the center 592 of the effective area 524 is aligned with the center 591 of the image area 521 . The centers of these areas are thus aligned with one another.

In this context, it should be noted that the width a of the shadow area 522 and the width b of the shadow area 523 are not limited to a certain length, as long as the two widths are the same. In order to achieve a stable stapling process, however, it is advantageous to set the widths as explained above.

The CCD image sensor 5 is designed such that the center 593 of the housing 50 is aligned with the center 591 of the image area 521 .

As a result, the center 593 of the housing 50 is aligned with the center 592 of the effective area 524 .

As shown in Fig. 4, can be positioned by using the CCD image sensor 5 with its just described construction of the latter relative to the optical imaging system without an adjustment spacer (centering means) on the outside of the CCD image sensor 5 , i.e. between the CCD image sensor 5 and the frame member 61 must be provided. It is thus possible to align the center of the optical imaging system with the center 592 of the effective area 524 without using a spacer. The center of the optical imaging system is given by the intersection of the optical axis O of the imaging system with the light receiving surface 52 .

Since no spacer is required, the number of components can be reduced be wrested.

In addition, since a spacer is not required, the outer diameter of the frame member 61 and thus the diameter of the opening 46 of the main body 2 can be reduced. It is thus possible to reduce the diameter of the main body 2 .

Since the center of the optical imaging system can be aligned with the center 592 of the effective area 524 without an eccentricity correcting and thus serving the centering adjustment, the number of work steps required for assembling the endoscope 1 is reduced, resulting in improved productivity leads.

The function channels provided in tip 21 of the main body 2 are explained below.

As shown in FIG. 4, the CCD image sensor 5 is disposed inside the opening 46 such that a straight line 65 that runs through the center 561 of the image area 521 and is parallel to the short sides 53a and 53b of the image area 521 , runs through the central axis 22 of the main body 2 . As explained before, the objective lens 33 , the convex lens 34 , the concave lens 35 , the convex lens 36 and the optical low-pass filter 37 are each arranged in front of the CCD image sensor 5 .

The instrument channel 41 is located near the long side 54 a of the CCD image sensor 5 in an eccentric position away from the central axis 22 .

The other channels are symmetrical net compared to the straight line 65 . Thus, the water supply channel 42 and the optical waveguide 44 are arranged near the short side 53a and the air supply channel 43 and the optical waveguide 45 near the short side 53b, with respect to the straight line 65 on the one hand the water supply channel 42 and the air supply channel 43 and on the other hand the optical waveguide 44 and the optical fiber 45 are arranged symmetrically to each other. As already explained above, the illumination lenses 31 and 32 are arranged at the tips of the optical waveguides 44 and 45 , respectively.

By arranging the function channels as just explained, the diameter of the main body 2 can be further reduced.

As shown in FIG. 1, a universal cable connection 25 is connected at one end to the base end of the main body 2 .

The other end of the cable connection 25 has a connecting section 26 which is equipped with a connecting part 27 . Via the connection part 27, the endoscope 1 is detachably electrically and optically ver connected with the light source apparatus. 8

A with the connector 27 electrically connected signal preprocessor 7 is housed in the connecting portion 26 . The CCD image sensor 5 is electrically connected to the signal preprocessing processor 7 via the pins 56 of the CCD image sensor 5 and signal lines 47 , 48 .

One ends of the optical waveguides 44 and 45 are in contact with the Be leuchtungslinsen 31 and 32 are arranged, while the base ends of the Lichtwel lenleiter 44 and 45 are connected to the terminal part 27th

As shown in FIG. 2, the signal preprocessing processor 7 of the endoscope 1 includes a sample and hold / color separation circuit 71 , a CCD processing circuit 72 (bracket circuit), a television timing generator 73 , a CCD timing generator 74 and a buffer 75 .

As shown in FIG. 1, the light source device 8 includes a lamp power source 81 , a lamp 82 as a light source, a condenser lens 83 , a lens element 84 , a system control circuit 85 , a light control circuit 86 and a signal processing circuit 9 . All of these components are housed in a housing, not shown.

As shown in Fig. 3, the signal processing circuit 9 of the light source device 8 includes a matrix circuit 91 , a gamma correction circuit 92 , an aperture correction circuit 93 , an A / D converter 94 , a timing generator 95, a memory 96 , a D / A converter 97 , a buffer 98 and a matrix encoder buffer circuit 99 .

At the light source device 8 , a television monitor 400 is also releasably closed, which images of the part to be observed, for. B. the diseased body part of the patient represents.

The operation of the electronic endoscope system 300 is described below.

As shown in FIG. 1, when the power supply of the light source 82 is switched on, electrical energy is supplied from the power supply 81 . As a result, illuminating light is emitted from the light source 82 onto the light entry end faces of the light waveguides 44 and 45 .

The illuminating light emitted by the light source 82 is first bundled by the condenser lens 83 and then passes through the aperture element 84 , which controls the illuminating light so that a certain amount of illuminating light strikes the light entry end faces of the optical fibers 44 and 45 . The operation of the aperture element 84 will be explained later.

The illuminating light then passes through the optical waveguides 44 and 45 and illuminates the part of the body to be observed via the illuminating lenses 31 and 32 .

The light reflected from this part is then passed through the objective lens 33 , the convex lens 34 , the concave lens 35 and the convex lens 36 , so as to generate an image on the light receiving surface 42 of the CCD image sensor 5 (see FIG. 4 ). At this time, the high-frequency wave components of the reflected light are eliminated by the optical low-pass filter 37 shown in FIG. 4.

In the meantime, according to FIG. 2, a horizontal synchronization signal HS and a vertical synchronization signal VS are generated in the TV timing generator 73 of the signal preprocessing processor 7 provided in the endoscope 1 . The signals HS and VS are supplied to both the CCD processing circuit 72 and the CCD timing generator 74 .

A synchronization signal Sync is also generated in the TV timing generator 73 . This is, as shown in FIGS . 1 and 3, both the system control circuit 85 and the timing generator 95 of the signal processing circuit 9 of the light source device 8 is supplied.

As shown in FIG. 2, on the basis of the synchronization signals HS and VS received from the TV timing generator 73 , drive signals are generated in the CCD timing control generator 74 , which are used to control the CCD image sensor 5 . These driver signals are output from the signal preprocessing processor 7 through the buffer 75 .

In the CCD timing generator 74 , a sample and hold signal is also generated, which is supplied to the sample and hold / color separation circuit 71 .

As shown in FIG. 1, the driver signals output from the signal preprocessing processor 7 are supplied via the signal lines 47 to the CCD image sensor 5 , which is driven on the basis of these driver signals. This control of the CCD image sensor 5 allows the latter to record the images of the part to be observed which are generated on the light receiving surface 52 , whereupon the CCD signals are output from the CCD image sensor 5 . This CCD Si gnale are supplied through the signal line 48 to the signal-to-end processor. 7

As shown in FIG. 2, the sample and hold / color separation circuit 71 of the signal preprocessing processor 7 separates the CCD signals according to the sample and hold signals SHP output from the CCD timing generator 74 into an R-, a- or a B color signal. R stands for red, G for green and B for blue. The R, G and B signals are then fed to the CCD processing circuit 72 .

As shown in FIG. 6, in the CCD timing generator 74 , clamp pulse signals continue to be clamped in synchronization with the timing control according to which the R, G and B signals from the pixels ei nes each shadow areas 522 and 523 are supplied to the CCD processing circuit 72 , and then the clamp pulse signals thus generated are each supplied to the CCD processing circuit 72 .

Thus, in a horizontal scan two spaced bracket pulses according to FIG. 6 are generated and these pulses are then fed to the CCD processing circuit 72 .

As shown in FIG. 7, the CCD processing circuit 72 executes two clamping processes in one horizontal scan, that is, for each horizontal scan.

In each bracket process, the R, G, and B signals are sampled in synchronization with the respective bracket pulse signal output from the CCD timing generator 74 . Namely, by sampling each of the R, G, and B signals from the pixels of the scan area 522 and 523 , a reference level for "optically black" can be detected as a reference black level, and this detected reference level can be held. The reference black level is also referred to below briefly as the reference level.

In the present embodiment, the CCD processing circuit 72 includes a capacitor, not shown, which is used as a means for holding the reference level. The capacitor is also designed so that it stores an amount of charge (voltage) corresponding to the reference level. The reference level can thus be obtained from the voltage value of the capacitor. In this case, although the bracket process can be performed once for each horizontal scan, since a bracket process is performed for the respective shadow areas in a single horizontal scan, an appropriate reference level is reliably obtained, and it is possible to to keep the reference level in a more stable manner.

As shown in Fig. 2, 72 suitable R, G and B signals can be obtained in that the Referenzpegelkompo component in the CCD processing circuit of the originating from the pixels of the effective range 524 of R, G and B Signals are subtracted. On the basis of such suitable signals, two color difference signals RY, BY and a luminance signal Y are generated. By subtracting the reference level component from the R, G and B signals, it becomes possible, for example, to use unnecessary signal components, e.g. B. to eliminate the dark current component or the like from such signals. This way you get good pictures.

As shown in Figs. 2 and 3, the color difference signals RY, BY and the luminance signal Y are output from the CCD processing circuit 72 and then supplied to the matrix circuit 91 of the signal processing circuit 9 provided in the light source device 8 . As shown in Fig. 1, the luminance signal is also supplied to the light control circuit 86 . The luminance signal is used in the diaphragm element 84 to regulate the amount of illuminating light. A reference voltage Vref which serves to regulate the illuminating light is fed to the light regulating circuit 86 by the system control circuit 85 . Based on the reference voltage Vref and the luminance signal Y, the light control circuit 86 generates a control signal which is used to control the lens element 84 .

As shown in Fig. 3, in the matrix circuit 91, the color difference signal RY, the color difference signal BY and the luminance signal Y are converted into the R, G and B signals.

After the corrections made by the gamma correction circuit 92 and the aperture correction circuit 93 , the R, G and B signals are supplied to the A / D converter 94 .

In the A / D converter 94 , the R, G and B signals supplied as analog signals are converted into digital signals.

These digital R, G and B signals are temporarily written into memory 96 . For example, based on data corresponding to the signals stored in memory 96 , a freeze operation can be performed to capture a desired still image.

The R, G and B signals are then read out from the memory 96 and fed to the D / A converter 97 .

In the D / A converter 97 , the R, G and B signals supplied as digital signals are converted into analog signals. The analog R, G and B signals are then fed to both the buffer 98 and the matrix encoder buffer circuit 99 .

In the matrix encoder buffer circuit 99 , based on the analog R, G and B signals output from the D / A converter 97 and the synchronization signal Sync output from the timing generator 95, a luminance signal Y, a color saturation signal C and a Component signal generated Compo site. The luminance signal Y, the color saturation signal C and the component signal Comp composite are output to an output terminal, not shown.

The R, G and B signals originating from the D / A converter 97 and the synchronization signal Sync originating from the timing generator 95 are fed to the television monitor 400 via the buffer 98 .

Then, a color image (electronic image) taken from the CCD image sensor 5 is displayed in the form of a moving image on the television monitor 400 .

As explained above, in the CCD image sensor 5 and the endoscope 1 according to the invention, the center of the optical imaging system can be aligned with the center 592 of the effective area 524 of the CCD image sensor 5 without any correction of the eccentricity and thus the centering serving Ju must be made. As a result, the number of steps required for assembling the endoscope 1 can be reduced. This leads to improved productivity.

In the present invention, it is not necessary to provide a spacer or a corresponding centering means on the outside of the CCD image sensor 5 . Since this can save space, the diameter of the opening 46 and thus the diameter of the main body 2 can be reduced.

Since no spacer is required, the number of components can be reduced be tied. This reduces manufacturing costs.

The electronic endoscope according to the invention can be used, for example, as a medical or as an industrial endoscope. Particularly when the endoscope is used as a medical endoscope, the load on the patient can be reduced by reducing the diameter of the main body 2 of the endoscope 1 .

The Ele described in the above-described embodiments elements can be replaced by other, functionally identical elements.  

For example, the CCD image sensor 5 provided in the illustrated exemplary embodiments can be replaced by image elements of different types, e.g. B. by a MOS picture element or a CPD, where CPD stands for Charge Priming De vice. In addition, either a color picture element or a monochrome picture element can be used.

In the exemplary embodiments explained, the picture element has a rectangular one Image area. However, the invention is not limited to this form. So is with for example, a square image area is also suitable.

Claims (9)

1. Picture element for an electronic endoscope, with an essentially rectangular image area, each on two opposite sides a band-shaped shadow area for capturing a reference Black level, with the two shadow areas essentially have the same width. 2. Picture element according to claim 1, characterized in that the two Sides of the image area related to a horizontal scanning direction in the Image element are arranged at both ends. 3. Picture element according to claim 1 or 2, characterized in that it is a Has housing and is designed so that the middle of the shadow area che not containing portion of the image area essentially at the Center of the housing is aligned. 4. Picture element according to one of the preceding claims, characterized through connectors arranged along two sides of the image area are perpendicular to the shadow areas. 5. Electronic endoscope with a picture element that is essentially one has rectangular image area, each on two opposite sides because a band-shaped shadow area for capturing a reference Black level, with the two shadow areas essentially have the same width. 6. Electronic endoscope according to claim 5, characterized in that the picture element is arranged in an end section of the endoscope and that the two sides of the picture element refer to a horizontal Ab scanning direction in the picture element are arranged at its two ends.   7. Electronic endoscope according to claim 5 or 6, characterized net that the picture element has a housing and is designed so that the Middle of a section of the image not containing the shadow areas is essentially aligned with the center of the housing. 8. Electronic endoscope according to one of claims 5 to 7, characterized net by a bracket circuit that is designed a bracket pro process to acquire the reference black level and then to maintain the detected reference black level during image acquisition. 9. Electronic endoscope according to claim 8, characterized in that the bracket circuit in every horizontal scan the bracket pro process for the respective shadow areas based on signals leads that come from pixels of a section that corresponds to the respective chat corresponds to the area of the image area.