JP3590907B2 - Imaging device - Google Patents

Description

ここで、κ，μはそれぞれ電磁シールド層の導電率及び透磁率であり、ベクトルＥ，Ｂはそれぞれ電界及び磁束密度である。
【００１８】
上記式から下記の２式が得られる。
【００１９】
【数２】

電磁シールド層内の位置で定まる電流と磁束密度分布は、次式となる。
【００２０】
【数３】

この関係式により、電磁シールド層４０の厚み（ｘ）方向の磁界Ｂ_ｚ 及び誘導電流ｉ_ｙ の分布は、次式で与えられる。
〔数４〕
Ｂ_ｚ ＝Ｋ_１ｅｘｐ｛− （ωκμ／２）^１／２ ・ｘ｝× ｃｏｓ｛ωｔ− （ωκμ／２）^１／２ ・ｘ｝
ｉ_ｙ ＝Ｋ_２ｅｘｐ｛− （ωκμ／２）^１／２ ・ｘ｝× ｃｏｓ｛ωｔ− （ωκμ／２）^１／２ ・ｘ｝
但し、Ｋ_{１ ，} Ｋ_２ はｘ＝０（シールド層表面）での磁界Ｂ_ｚ 及び誘導電流ｉ_ｙ の値である。
【００２１】
上記式からも明らかなように磁界Ｂ_ｚ 及び誘導電流ｉ_ｙ の値は、シールド層の厚みｘが大きくなるにしたがって指数関数的に減衰し、厚みｘが、次式、
（２／ωκμ）^１／２ ≦ｘ
を満たすようにすると、磁界Ｂ_ｚ 及び誘導電流ｉ_ｙ の値は、１／ｅ （≒０．３６８）以下に減衰することになる。
【００２２】
また、上記シールド層の厚みｘを決定するためのパラメータとして、減衰すべき周波数ｆ（＝ω／２π）があるが、この周波数ｆを、例えば３００ＫＨｚとすると、それ以上の周波数の高周波電流、即ち、高周波焼灼電源装置２８から発生される使用範囲の高周波電流（３００ＫＨｚ〜５ＭＨｚ ）に対しても充分目的を達成することができる。
【００２３】
図２は図１の要部拡大図である。
同図に示すように、ＣＣＤ１４の入射光窓（カバーガラス）１４Ａ及びＣＣＤ基板１４Ｂを含む表面全体が電磁シールド層４０によって被覆されているが、入射光窓１４Ａの表面には、透明ネサ膜（例えば、Ｃｕ，Ｉｎ又はその酸化膜）を用いる。
【００２４】
尚、１ＭＨｚ 程度の高周波電流に対しては、シールド層の厚さは、非磁性部材を用いると、数ミクロン〜数十ミクロン程度となり、入射光透過率を考慮して決めることになる。即ち、入射光窓１４Ａに蒸着されるシールド層の厚さｘは、上記不等式を満たすように選定する必要があるが、その上限の厚みは、光の透過率を規定する厚みによって規制される。
【００２５】
一方、入射光窓１４Ａ以外のシールド層の厚みは、数十ミクロン〜数百ミクロン又は、上記不等式を考慮しつつ多少厚めにする。尚、入射光窓１４Ａのシールド層と、それ以外のシールド層とは同電位になるように電気的に接続されている。
このように外周電磁シールド部材３６を設けるとともに、入射光窓１４等を含むＣＣＤ１４の表面全体を電磁シールド層４０で被覆することにより、光電変換部の高周波焼灼電源装置２８からの高周波電流による電磁波に対して良好な電磁シールドが達成できる。
【００２６】
尚、上記第１実施例では、外周電磁シールド部材３６によって二重にシールドしているが、本発明はこれに限らず、外周電磁シールド部材３６を取り除いてもよく、この場合には挿入部先端１０の細径化を図ることができる。
図３は本発明の第２実施例を示す要部構成図である。尚、図２と共通する部分には同一の符号を付し、その詳細な説明は省略する。
【００２７】
この第２実施例では、図３に示すようにＣＣＤ１４等には電磁シールド層を設けずに、外周電磁シールド部材３６の前面開口部分に透明ガラス４２を配設し、この透明ガラス４２上に、前記ＣＣＤ１４の入射光窓１４Ａに蒸着したシールド層と同様な電磁シールド層４４が蒸着されている。また、この電磁シールド層４４は外周電磁シールド部材３６と同電位になるように電気的に接続されている。
【００２８】
尚、第２実施例において、ＣＣＤ１４の入射光窓１４Ａを除く表面を第１実施例と同様に電磁シールド層で被覆するようにしてもよい。
図４は本発明の第３実施例を示す要部構成図である。尚、図３と共通する部分には同一の符号を付し、その詳細な説明は省略する。
この第３実施例は、図３の透明ガラス４２の代わりにプリズム４６を利用するようにした点で、第２実施例と相違する。即ち、このプリズム４６は、その入射面が外周電磁シールド部材３６の前面開口部分まで延出しており、このプリズム４６の入射面上に電磁シールド層４８が蒸着されている。また、この電磁シールド層４８は外周電磁シールド部材３６と同電位になるように電気的に接続されている。
【００２９】
尚、本発明は電子内視鏡装置に限らず、例えば、溶接作業を行う機器等にも適用でき、要は固体撮像素子からの信号に基づいて被写体をモニタＴＶに表示し、その画像を見ながら高周波電流等を使用して作業を行うものであれば、如何なるものにも適用できる。
【００３０】
【発明の効果】
以上説明したように本発明に係る撮像装置によれば、固体撮像素子の表面及び又は周囲全体を電磁シールドするとともに、少なくとも固体撮像素子の入射光路上に設けられる電磁シールド層の厚さを、処置中に発生する高周波電流の周波数に応じた好適な厚さにしたため、固体撮像素子等を介してＴＶ画面に表示される画像上のノイズを大幅に低減することができる。特に、固体撮像素子への入射光透過率を低下させることなく、効率良くノイズを防止することができる。また、固体撮像素子の表面を電磁シールド層で被覆するとともに、外周電磁シールド部材で固体撮像素子等を囲繞して二重シールド構造にすることにより、６０Ｈｚ 等の低周波数ノイズにも対応することができる。
【図面の簡単な説明】
【図１】図１は本発明に係る撮像装置が適用された電子内視鏡装置の第１実施例を示す全体構成図である。
【図２】図２は図１の要部拡大図である。
【図３】図３は本発明の第２実施例を示す要部構成図である。
【図４】図４は本発明の第３実施例を示す要部構成図である。
【符号の説明】
１０…挿入部先端
１２…撮像レンズ
１３、４６…プリズム
１４…ＣＣＤ
１４Ａ…入射光窓（カバーガラス）
１４Ｂ…ＣＣＤ基板
２０…患部
２２…ケーブル
２４…高周波止血具
２６…処置具挿通チャンネル
２８…高周波焼灼電源装置
３６…外周電磁シールド部材
３８…シールド外皮線
４０、４４、４８…電磁シールド層
４４…透明ガラス[0001]
[Industrial applications]
The present invention relates to an imaging device, and more particularly to an imaging device having a solid-state imaging device and used together with a treatment device that induces electromagnetic noise in an output signal of the solid-state imaging device.
[0002]
[Prior art]
As this type of imaging apparatus, there is an electronic endoscope apparatus used in combination with a high-frequency ablation power supply apparatus, a YAG laser apparatus, or the like.
Generally, an imaging lens, a solid-state imaging device (CCD), and the like are provided at the distal end of an insertion portion of an electronic endoscope, and an observation image is formed on the CCD via the imaging lens, and is subjected to photoelectric conversion. The electric signal representing the photoelectrically converted observation image is output to a monitor TV after being appropriately processed by a processor. Thereby, an observation image can be displayed on the monitor TV.
[0003]
On the other hand, a high-frequency treatment tool such as a high-frequency hemostat, a high-frequency snare, and a high-frequency knife is inserted into the treatment tool insertion channel of the electronic endoscope while viewing the image projected on the monitor TV, and the high-frequency ablation power supply device A treatment such as hemostasis / cut of an affected part is performed by flowing a high-frequency current through a treatment tool. For example, when performing hemostatic treatment, a high-frequency current in the range of 300 KHz to 5 MHz is intermittently supplied from a high-frequency ablation power supply to a high-frequency hemostatic device.
[0004]
However, during the hemostatic treatment, the energy of the electromagnetic wave due to the high-frequency current flowing through the lead wire portion and the affected part of the high-frequency hemostatic device is applied to the CCD and its peripheral circuits, and is superimposed as a noise signal on the CCD output signal. There has been a problem that it is significantly reduced.
Conventionally, in order to prevent this, the distal end of the insertion portion, the CCD and its peripheral circuits are electromagnetically shielded, and in particular, an electromagnetic shield layer having light transmittance is provided on the light receiving surface of the CCD so that the entire CCD is electromagnetically shielded. Some are also disclosed (JP-A-5-56916).
[0005]
[Problems to be solved by the invention]
By the way, the thickness of the electromagnetic shield layer described in the above-mentioned Japanese Patent Application Laid-Open No. 5-56916 is a predetermined thickness so as to optimize the light transmittance. However, light is also a kind of electromagnetic wave, and there is a problem that the effect of the electromagnetic shield is lost if the thickness of the electromagnetic shield layer is determined so as to optimize the light transmittance.
[0006]
The present invention has been made in view of such circumstances, and it is possible to efficiently prevent noise without lowering the transmittance of incident light to a solid-state imaging device and use a high-frequency current or the like that generates an electromagnetic wave. It is an object of the present invention to provide an imaging device capable of viewing a good image even during a treatment.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a solid-state imaging device, an imaging apparatus used in conjunction with a treatment device that induces electromagnetic noise in the output signal of the solid-state imaging device, the incident light path to the solid-state imaging device, Surrounding the solid-state imaging device except for the opening, and providing an outer peripheral electromagnetic shield member that electromagnetically shields even a frequency equal to or lower than the frequency of the electric signal used in the treatment device, and sets the conductivity of the electromagnetic shield layer to κ. , The magnetic permeability is μ, and the electromagnetic shield frequency, which is the frequency of the electric signal used in the treatment device, is f, the thickness x of the electromagnetic shield layer is represented by the following formula:
(2 / ωκμ) ^1/2 ≤x
Where ω = 2πf
Is deposited on the entire surface including the incident light window of the solid-state imaging device and the substrate of the solid-state imaging device, and the electromagnetic shielding layer and the outer peripheral electromagnetic shielding member are connected to have the same potential. it is characterized in that.
[0008]
[Action]
According to the present invention, the thickness x of the electromagnetic shield layer is expressed by the following formula:
(2 / ωκμ) ^1/2 ≦ x
Since the electromagnetic shield layer is provided so as to satisfy the condition, the electromagnetic shielding can be performed so that the electromagnetic wave energy incident on the solid-state imaging device is smaller than about 1/3. Accordingly, it is possible to suppress a decrease in image quality during a treatment using a high-frequency current or the like that generates an electromagnetic wave.
[0009]
【Example】
Hereinafter, preferred embodiments of an imaging device according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing a first embodiment of an electronic endoscope apparatus to which an imaging apparatus according to the present invention is applied, and shows a case where hemostatic treatment is performed using a high-frequency ablation power supply apparatus.
[0010]
An imaging lens 12, a prism 13 and a CCD 14 are provided at a distal end 10 of an insertion portion of the electronic endoscope apparatus. The imaging lens 12 captures an image of an affected part 20 illuminated via a light guide 16 and a lens 18. Then, the image is formed on the light receiving portion of the CCD 14 via the prism 13, and the CCD 14 photoelectrically converts the incident light and outputs the CCD output to a processor (not shown) via the cable 22.
[0011]
The processor outputs a signal for controlling the driving of the CCD 14 to the CCD 14 via the cable 22, inputs a CCD output signal output from the CCD 14 via the cable 22, and processes the signal to generate a video signal. The video signal is output to a monitor TV (not shown). Thereby, an image of the affected part 20 is displayed on the monitor TV.
[0012]
On the other hand, the high-frequency hemostatic device 24 is inserted into the treatment tool insertion channel 26 of the endoscope, and the distal end of the high-frequency hemostatic device 24 extends from the distal end 10 of the insertion section to the diseased part 20 while watching the image displayed on the monitor TV. It is extended toward. The high-frequency hemostatic device 24 is electrically connected to the high-frequency ablation power supply device 28.
When the foot switch 30 is operated, the high-frequency ablation power supply device 28 outputs a high-frequency hemostatic / cut operation signal of 300 KHz to 5 MHz corresponding to the hemostatic or cut treatment content to the high-frequency treatment device. Incidentally, 32 is an electrode plate, and 34 is an insulator.
[0013]
By the way, at the time of hemostasis treatment, an electromagnetic wave is propagated to the entire region of the insertion portion distal end 10 by a high-frequency current flowing from the high-frequency ablation power supply 28 to the high-frequency hemostatic device 24 and the human body. This electromagnetic wave becomes a noise signal to the CCD 14 and the cable 22. To prevent the noise signal from entering the CCD 14 and the cable 22, the outer peripheral electromagnetic wave that surrounds the CCD 14 and the like except for the incident optical path of the CCD 14 is provided at the tip 10 of the insertion portion. The shield member 36 is provided, and the cable 22 is provided with a shield sheath 38 around the cable 22. The outer electromagnetic shield member 36 is designed so as to be able to shield, for example, electromagnetic waves of 60 Hz or higher.
[0014]
Further, the entire surface of the CCD 14 including the incident light window is covered with the electromagnetic shield layer 40. The outer peripheral electromagnetic shield member 36 and the electromagnetic shield layer 40 are electrically connected to each other so as to have the same potential as the shield outer conductor 38 of the cable 22.
Next, details of the electromagnetic shield layer 40 will be described.
[0015]
First, a case where an electromagnetic wave accompanying the high-frequency current is incident on the electromagnetic shield layer 40 formed in the incident light window of the CCD 14 will be considered.
Now, electromagnetic waves and the magnetic field H _Z parallel to the electromagnetic shielding layer just prior to entering the arbitrary infinitesimal plane of the electromagnetic shield layer,
H _z = H ₀ exp (jωt)
And Here, ω = 2πf, where f is the frequency of the high-frequency current. In addition, the magnetic field is only the Z component even in the electromagnetic shield layer.
[0016]
On the other hand, the current density (vector i) in the electromagnetic shield layer (conductor) and the magnetic field strength (vector H) have the following relationship.
[0017]
(Equation 1)

Here, κ and μ are the conductivity and the magnetic permeability of the electromagnetic shield layer, respectively, and the vectors E and B are the electric field and the magnetic flux density, respectively.
[0018]
The following two equations are obtained from the above equations.
[0019]
(Equation 2)

The current and magnetic flux density distribution determined at a position in the electromagnetic shield layer are represented by the following equations.
[0020]
(Equation 3)

This relationship, the distribution of the magnetic field B _z and the induced current i _y of the thickness of the electromagnetic shield layer 40 (x) direction is given by the following equation.
[Equation 4]
B _z = K ₁ exp ｛− (ωκμ / 2) ^1/2 · x｝ × cos {ωt− (ωκμ / 2) ^1/2 · x｝
i _y = K ₂ exp ｛− (ωκμ / 2) ^1/2 · x｝ × cos {ωt− (ωκμ / 2) ^1/2 · x｝
Here, K _{1 and} K ₂ are the values of the magnetic field B _z and the induced current i _y at x = 0 (the shield layer surface).
[0021]
As is clear from the above equation, the values of the magnetic field B _z and the induced current i _y attenuate exponentially as the thickness x of the shield layer increases, and the thickness x becomes
(2 / ωκμ) ^1/2 ≦ x
When the value is _satisfied , the values of the magnetic field B _z and the induced current i _y are attenuated to 1 / e (≒ 0.368) or less.
[0022]
As a parameter for determining the thickness x of the shield layer, there is a frequency f to be attenuated (= ω / 2π). If the frequency f is, for example, 300 KHz, a high-frequency current of a frequency higher than that, that is, The purpose can be sufficiently achieved even for a high-frequency current (300 KHz to 5 MHz) in a use range generated from the high-frequency ablation power supply device 28.
[0023]
FIG. 2 is an enlarged view of a main part of FIG.
As shown in the figure, the entire surface including the incident light window (cover glass) 14A and the CCD substrate 14B of the CCD 14 is covered with the electromagnetic shield layer 40, and the surface of the incident light window 14A is covered with a transparent Nesa film ( For example, Cu, In or an oxide film thereof is used.
[0024]
For a high-frequency current of about 1 MHz, the thickness of the shield layer is about several microns to several tens of microns when a non-magnetic member is used, and is determined in consideration of the incident light transmittance. That is, the thickness x of the shield layer deposited on the incident light window 14A needs to be selected so as to satisfy the above inequality, but the upper limit thickness is regulated by the thickness that regulates the light transmittance.
[0025]
On the other hand, the thickness of the shield layer other than the incident light window 14A is several tens of microns to several hundreds of microns, or slightly larger in consideration of the inequality. The shield layer of the incident light window 14A and the other shield layers are electrically connected so as to have the same potential.
By providing the outer electromagnetic shield member 36 and covering the entire surface of the CCD 14 including the incident light window 14 and the like with the electromagnetic shield layer 40 in this manner, the electromagnetic wave generated by the high-frequency current from the high-frequency ablation power supply device 28 of the photoelectric conversion unit is reduced. Good electromagnetic shielding can be achieved.
[0026]
In the first embodiment, double shielding is performed by the outer peripheral electromagnetic shield member 36. However, the present invention is not limited to this, and the outer peripheral electromagnetic shield member 36 may be removed. 10 can be reduced in diameter.
FIG. 3 is a main part configuration diagram showing a second embodiment of the present invention. Note that parts common to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0027]
In the second embodiment, as shown in FIG. 3, a transparent glass 42 is disposed on the front opening of the outer peripheral electromagnetic shield member 36 without providing an electromagnetic shield layer on the CCD 14 or the like. An electromagnetic shield layer 44 similar to the shield layer deposited on the incident light window 14A of the CCD 14 is deposited. The electromagnetic shield layer 44 is electrically connected to the outer electromagnetic shield member 36 so as to have the same potential.
[0028]
In the second embodiment, the surface of the CCD 14 except for the incident light window 14A may be covered with an electromagnetic shield layer as in the first embodiment.
FIG. 4 is a main part configuration diagram showing a third embodiment of the present invention. Note that the same reference numerals are given to portions common to FIG. 3 and detailed description thereof is omitted.
The third embodiment differs from the second embodiment in that a prism 46 is used instead of the transparent glass 42 of FIG. That is, the entrance surface of the prism 46 extends to the front opening of the outer peripheral electromagnetic shield member 36, and the electromagnetic shield layer 48 is deposited on the entrance surface of the prism 46. The electromagnetic shield layer 48 is electrically connected to the outer electromagnetic shield member 36 so as to have the same potential.
[0029]
The present invention is not limited to the electronic endoscope apparatus, but can be applied to, for example, equipment for performing a welding operation. In short, the present invention displays a subject on a monitor TV based on a signal from a solid-state imaging device and views the image. However, the present invention can be applied to any operation that uses a high-frequency current or the like.
[0030]
【The invention's effect】
As described above, according to the imaging apparatus of the present invention, the surface and / or the entire periphery of the solid-state imaging device is electromagnetically shielded, and at least the thickness of the electromagnetic shielding layer provided on the incident optical path of the solid-state imaging device is reduced. Since the thickness is set to a suitable value according to the frequency of the high-frequency current generated therein, noise on an image displayed on a TV screen via a solid-state imaging device or the like can be significantly reduced. In particular, noise can be efficiently prevented without lowering the transmittance of incident light to the solid-state imaging device. In addition, by covering the surface of the solid-state imaging device with an electromagnetic shield layer and surrounding the solid-state imaging device with an outer electromagnetic shielding member to form a double shield structure, it is possible to cope with low-frequency noise such as 60 Hz. it can.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a first embodiment of an electronic endoscope apparatus to which an imaging device according to the present invention is applied.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a main part configuration diagram showing a second embodiment of the present invention.
FIG. 4 is a main part configuration diagram showing a third embodiment of the present invention.
[Explanation of symbols]
Reference numeral 10: insertion portion tip 12: imaging lens 13, 46 ... prism 14: CCD
14A: Incident light window (cover glass)
14B ... CCD board 20 ... Affected part 22 ... Cable 24 ... High frequency hemostat 26 ... Treatment tool insertion channel 28 ... High frequency cautery power supply 36 ... Outer circumference electromagnetic shield member 38 ... Shield outer sheath wire 40,44,48 ... Electromagnetic shield layer 44 ... Transparent Glass

Claims (1)

An imaging apparatus having a solid-state imaging device and used together with a treatment device that induces electromagnetic wave noise in an output signal of the solid-state imaging device,
Surrounding the solid-state imaging device except for an opening serving as an optical path of light incident on the solid-state imaging device, and providing an outer peripheral electromagnetic shield member that electromagnetically shields even a frequency equal to or lower than a frequency of an electric signal used in the treatment device. ,
When the conductivity of the electromagnetic shield layer is κ, the magnetic permeability is μ, and the electromagnetic shield frequency which is the frequency of the electric signal used in the treatment device is f, the thickness x of the electromagnetic shield layer is represented by the following formula:
(2 / ωκμ) ^1/2 ≤x
Where ω = 2πf
Is deposited on the entire surface including the incident light window of the solid-state imaging device and the substrate of the solid-state imaging device, and the electromagnetic shielding layer and the outer peripheral electromagnetic shielding member are connected to have the same potential. An imaging device characterized by the above-mentioned.

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