JP2565903B2 - Endoscopic imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an endoscope imaging apparatus provided with means for improving frequency characteristics.

[Prior Art] In recent years, by inserting an elongated insertion portion, an observation means provided on the distal end side of the insertion portion can be used to observe the inside of a living body without requiring an incision, and a treatment instrument can be used as necessary. Endoscopes that can be used for medical treatment have become widely used.

In addition, recently, without using an image guide with a fiber bundle, an optical image is formed on an image pickup surface of a solid-state image pickup device by an objective lens, and a photoelectrically converted video signal is guided to a signal processing means by a signal cable. Mirrors (hereinafter referred to as electronic endoscopes or electronic scopes) are in practical use.

A signal cable as a transmission system for transmitting an output signal of the solid-state imaging device (hereinafter referred to as SID) is generally matched as shown in FIG.

The output of the charge-coupled device (referred to as CCD) as SID is
It is applied via resistor 1 to the base of a transistor 2 which forms an emitter follower. The collector of the transistor 2 is connected to the power supply terminal Vc, and the emitter of the transistor 2 is grounded via the resistor 3 having a small resistance value and is also connected to one end of the transmission coaxial cable 4 via the resistor r.

The resistance r (whose resistance value is r) is matched by using one having a value equal to the characteristic impedance r of the coaxial cable 4. In other words, the output side has a sufficiently low output impedance, that is, a low impedance, and is connected to the coaxial cable 4 via the resistance r equal to the characteristic impedance r of the coaxial cable 4 for matching.

The output side end of the coaxial cable 4 is grounded via a resistor r having an impedance r equal to that of the coaxial cable 4, and is connected to an input end of a preamplifier or the like having a high input impedance, that is, a high impedance, to receive it. Matches on the side as well.

By the way, it has an elongated insertion part that can be inserted into a body cavity like an electronic endoscope, and the SID such as CCD is attached to the tip of this insertion part.
When a device such as an amplifier for amplification is built in, making the tip as thin as possible can reduce the pain to the patient at the time of insertion, and it can be inserted into a narrow insertion path for diagnosis. There are advantages.

[Problems to be Solved by the Invention] However, in an endoscope in which a SID such as CCD is built in the tip of the insertion portion, this SID is driven in addition to the SID at the tip, or the output signal of the SID is amplified. It requires various vices to be installed, which hinders the reduction of the diameter of the insertion part.

The present invention has been made in view of these circumstances, and provides an endoscope imaging apparatus capable of reducing the diameter of an endoscope insertion portion by minimizing the number of devices provided in the insertion portion distal end portion. The purpose is to do.

[Means and Actions for Solving the Problem] In order to achieve the above-mentioned object, an endoscope imaging apparatus according to the present invention is provided with a solid-state image sensor provided at a distal end of an elongated insertion section and a solid-state image sensor provided near the solid-state image sensor. A signal output end of the solid-state imaging device is connected to the base, a power supply end is connected to the collector, and an emitter of the transistor has one end connected to the signal line inserted into the insertion portion,
A resistor connected to the other end of the signal line and grounding the signal line to a reference potential, and transmitting the output signal of the solid-state imaging device to a signal processing circuit in a subsequent stage by the transistor, the signal line, and the resistor. It is characterized in that an emitter follower is formed.

With this configuration, the electric devices arranged in the distal end portion of the insertion portion can be minimized.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 relate to the first embodiment of the present invention.
FIG. 1 is an explanatory diagram showing the configuration of the main part of the first embodiment, and FIG. 2 is a characteristic diagram of the transmission system.

In FIG. 1, reference numeral 7 is a CCD, which is disposed in the distal end portion of the endoscope insertion portion and at the image forming position of an image pickup optical system (not shown), and the output side of this CCD 7 serves as the base of the current amplification transistor 2. The emitter of the transistor 2 is directly connected to the end of the coaxial cable 4. The collector of the transistor 2 is connected to the power supply terminal Vc. The coaxial cable 4 includes an endoscope insertion portion (not shown),
It is inserted into the operation section or the universal cord, and is connected to the camera controller via the connector. Then, in the camera controller, the end of the coaxial cable 4 is grounded via the emitter resistance r1 of the transistor 2 and is in parallel with the resistance r1 and is grounded via the series circuit of the capacitor C and the resistance r2. Connected to the input terminal of the preamplifier 6 having an input impedance of Z, and matched so that the combined impedance of the resistance r1, the capacitor C and the resistance r2, and the impedance Z of the preamplifier 6 in parallel becomes equal to the characteristic impedance of the coaxial cable 4. Has been taken.

In the configuration of this embodiment, the transistor 2 is provided in the tip portion of the endoscope insertion portion as an electric device required for CCD.
By arranging only the resistor, it is possible to omit the resistor, which has been arranged in the conventional example shown in FIG.

In the structure of the first embodiment, while having the above-mentioned effect, since the resistance on the sending side of the coaxial cable 4 is not provided, the matching becomes insufficient and the CCD drive clock used for reading the pixel signal from the CCD7 is The CCD clock frequency fo applied to may be reflected. As a result, as shown in FIG. 2, a peak occurs in the frequency characteristic and group delay characteristic of the cable at the clock frequency fo, and it becomes impossible to obtain a flat characteristic with respect to the frequency, so that the subject can be reproduced faithfully. It may run out.

In view of the above, the following embodiment is an example in which the transmission cable has a flat characteristic without causing peaks in the frequency characteristic and the group delay characteristic.

3 to 7 relate to the second embodiment of the present invention, FIG. 3 shows the structure of the main part of the second embodiment, and FIG.
FIG. 5 shows the overall configuration of the embodiment, FIG. 5 shows the combined impedance of the series circuit, FIG. 6 shows the combined impedance at the termination of the coaxial cable when the series circuit is provided, and FIG. 7 shows frequency characteristics and group delay characteristics of a transmission system in the case where the is provided.

An endoscope imaging apparatus 11 of the second embodiment has an electronic endoscope (also referred to as an electronic scope) 13 having an elongated insertion portion 12 as shown in FIG. 4, and a universal extended from the electronic scope 13. An image output from a camera control unit (or a video processor unit) 17 in which the end of the cord 14 is connectable and which houses the light source unit 15 and the signal processing unit 16 and this camera control unit (hereinafter referred to as CCU) 17. Color monitor that captures signals and displays them in color 18
Composed of and.

A light guide 19 for transmitting illumination light is inserted into the insertion portion 12 and the universal cord 14, and illumination light is supplied from a light source unit 15 to an incident end surface of the light guide 19. The light source unit 15 drives the white light of the white lamp 21 into a motor.
The light is guided to the incident end face of the light guide 19 by the condenser lens 24 through the rotary filter 23 which is rotationally driven by 22.
The rotary filter 23 is provided with red, green, and blue transmission filters (not shown), and these transmission filters are sequentially inserted in the optical path, so that the subject is illuminated with red, green, and blue illumination light. Will be done.

An objective lens 25 as an imaging optical system is provided at the tip of the insertion portion 12, and a charge coupled device (hereinafter referred to as CCD) 26 as a solid-state image pickup device is provided at the focal plane of the objective lens 25. Has been done. This CCD 26 has multiple coaxial cables 27,2
CCD from the drive circuit 28 in the CCU 17 via 7, ..., 27
Drive signal is applied. By applying this drive signal, the signal photoelectrically converted by the CCD 26 and stored as electric charge is output. The signal output from the CCD 26 is applied to the base of the transistor 31 as shown in FIG. 3, current-amplified and connected from the emitter to the emitter, and passes through the coaxial cable 32 forming the transmission system to terminate the circuit.
Entered in 33.

After the frequency characteristics and the group delay characteristics are matched by the termination circuit 33, they are amplified by the preamplifier 34 and then input to the video signal processing circuit 35 to generate a composite video signal (or three primary color signals), and the color monitor Colored at 18.

By the way, the termination circuit 33, which is the main part of the second embodiment, grounds the termination of the coaxial cable 32 by the bias resistor R1 of the transistor 31, as shown in FIG. It is grounded via a series circuit 36 of C1, a coil (inductance) L1, and a resistor R2.

The end of the coaxial cable 32 is grounded via a bias resistor R1 and a series circuit 36 of a capacitor C1, an inductance L1 and a resistor R2, and is input to a preamplifier 34.

Matching with the coaxial cable 32 is made by the combined impedance of the bias resistor R1, the series circuit 36 of the capacitor C1, the inductance L1, and the resistor R2, and the input impedance Zi of the preamplifier 34 connected in parallel.

For example, in FIG. 3, when there is no inductance L1, the clock frequency f of the CCD drive signal is as shown in FIG.
It has a peak because reflection occurs at o. That is,
At this time, the terminal impedance has a peak with respect to the frequency at the clock frequency fo of the CCD drive signal as shown by the dotted line in FIG.

In order to prevent this peak from occurring, in the second embodiment, the inductance L1 is further interposed in series with the capacitor C1 to form the series circuit 36 including the capacitor C1, the inductance L1 and the resistor R2. Then, the capacitor C1 and the inductance L1 are made to resonate in series at the clock frequency fo,
As shown in FIG. 5, the impedance is lowered and the resistance R2 prevents the impedance from becoming unnecessarily small, and the peak portion of the impedance shown by the dotted line in FIG. 6 is corrected. Matching is performed so that the impedance is almost constant with respect to the frequency. In this way, as shown in FIG. 7, the frequency characteristic and the group delay characteristic in the transmission system of the coaxial cable 32 in the case where the terminating circuit 33 in the second embodiment is provided are flat with respect to the frequency so that they do not depend on the frequency. Has improved.

The values of the capacitor C1 and the inductance L1 in the termination circuit 33 are set so that the resonance frequency of the capacitor C1 and the inductance L1 becomes the clock frequency fo of the CCD 26.

That is, the combined impedance of the termination circuit in the case of the clock frequency fo of the drive signal of the CCD 26 is R1R2Zi. Here, it is shown that they are combined in parallel. The combined impedance Z of the series circuit 36 is Since the setting is such that X = Xc when the frequency f is fo, Z = R2. Here, X is the inductive reactance of the coil, and Xc is the capacitive reactance of the capacitor.

In this way, connect the capacitor to the end of the coaxial cable 32.
By providing the series circuit 36 composed of C1, the inductance L1 and the resistor R2, the frequency characteristic and the group delay characteristic in the case of using the coaxial cable 32 can be made flat, and the imaged subject is faithful without depending on the frequency component. Can be played back.

FIG. 8 shows the main part of the third embodiment of the present invention. In this second embodiment, the termination circuit 41 is replaced with a series circuit 42 in parallel with the resistor R1.
As this, the capacitor C2 and the coil (which are also denoted by L2 also serving as the inductance) which does not have the resistor R2 in the first embodiment are used.

The series resonance frequency f _R of the capacitor C2 and the coil L2 is
As shown in FIG. 9, it is set to a value higher than the clock frequency fo, and as it approaches the clock frequency fo from the lower side of the clock frequency fo, the series circuit 42
It is set so as to compensate for a peak in the impedance of the transmission system in the conventional example (shown by the dotted line in FIG. 9),
As shown in FIG. 10, matching is performed so that the impedance becomes flat up to the clock frequency fo. It should be noted that although there is no matching at a frequency higher than this clock frequency fo, the signal band to be read is a frequency band of 0 to fo, so that there is almost no problem.

In the third embodiment, the series circuit 42 of the capacitor C2 and the coil L2 is used, but as shown in FIG. The combined impedance of the circuit 51 may be set as shown in FIG. 12 so that the circuit 51 is matched up to at least the clock frequency fo.

If there is a convex portion or a concave portion at a frequency lower than the clock frequency, compensation can be performed by providing a second embodiment or a parallel resonant circuit.

[Effects of the Invention] As described above, according to the present invention, there is an effect that the electric devices arranged in the distal end portion of the insertion portion can be reduced as much as possible, and the diameter of the endoscope insertion portion can be reduced.

[Brief description of drawings]

1 and 2 relate to a first embodiment of the present invention. FIG. 1 is an explanatory view showing the main part of the first embodiment, FIG. 2 is a characteristic diagram of a transmission system, and FIGS. FIG. 3 relates to the second embodiment of the present invention, FIG. 3 is a circuit diagram showing a main part of the second embodiment, FIG. 4 is a configuration diagram showing the whole of the second embodiment, and FIG. 5 is a series circuit. FIG. 6 is a characteristic diagram showing combined impedance, FIG. 6 is a characteristic diagram showing impedance of the transmission system with respect to frequency in the second embodiment, and FIG. 7 is a characteristic diagram showing frequency characteristics and group delay characteristic of the transmission system in the second embodiment. FIG. 8 is a circuit diagram showing a main part of a third embodiment of the present invention, FIG. 9 is a characteristic diagram showing an impedance of a series circuit in the third embodiment, and FIG. 10 is a transmission system in the third embodiment. 11 is a characteristic diagram showing the impedance of FIG. 11, FIG. 11 is a circuit diagram showing the main part of the fourth embodiment of the present invention, and FIG. Characteristic diagram showing the combined impedance of the series circuit in the embodiment, FIG. 13 is a configuration diagram of a main portion in the conventional example. 11 …… Endoscope imaging device, 13 …… Electronic scope 15 …… Light source, 16 …… Signal processor 17 …… CCU, 18 …… Color monitor 7.26 …… CCD, 2.31 …… Transistor 4.32 …… Coaxial cable , 33 ... Termination circuit 34 ... Preamplifier, 36 ... Series circuit

Claims (1)

(57) [Claims] 1. A solid-state image sensor provided at the tip of an elongated insertion section, a solid-state image sensor provided in the vicinity of the solid-state image sensor, a signal output terminal of the solid-state image sensor is connected to a base, and a power source terminal is connected to a collector. A transistor connected to the emitter of the transistor, one end of which is connected to the emitter of the transistor, and the other end of which is connected to the signal line, and the resistor which grounds the signal line to a reference potential. An emitter follower for transmitting an output signal of the solid-state image pickup device to a signal processing circuit at a subsequent stage is formed by the transistor, the signal line, and the resistor.