JPH0322769B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an endoscope device, and particularly to an endoscope device that has a built-in solid-state imaging device such as a charge-coupled device (CCD) at its tip and images an object. Regarding.

[Conventional technology]

In recent years, with the development of solid-state imaging devices, endoscopy is a system in which a solid-state imaging device such as a CCD is built into the tip of an endoscope to image the inside of the body cavity, display the image inside the body cavity on a monitor device, and make a diagnosis by looking at this display. A mirror device has been developed. In order to miniaturize the tip of the endoscope, such devices incorporate only the solid-state image sensor at the tip, and the drive circuit is located elsewhere, usually as a separate component from the endoscope. It is provided within the setter unit, and the drive signal is transmitted to the tip of the endoscope via a signal transmission cable within the endoscope. in general,
The processor unit also includes a light source.

As a conventional example of such an endoscope device, there is a video endoscope device described in Japanese Patent Laid-Open No. 60-80429. This device includes a video processor having a light source, a video monitoring device connected to the processor, and an insertion tube having a semiconductor imaging device at its distal end. An interface module is provided for removably connecting the insertion tube to the processor. Here, the semiconductor image device is driven by signals from a processor. Since there are slight differences in the characteristics of various imaging devices, means are provided within the interface module to adjust the drive signals to compensate for these differences. Therefore, different insertion tubes can be connected to the processor. The adjusting means includes variable resistors that adjust the positive and negative voltages of the clock signal, respectively, and adjusts the level of the drive signal.

[Problem to be solved by the invention]

In this conventional example, the level of the drive signal can be optimized to suit each image device, but when the drive circuit (processor) and the image device are configured separately as in this conventional example, , the following problems also arise. The processor and the image device are connected by a signal transmission cable, and a drive signal is transmitted via this cable, but the waveform of the transmitted drive signal may deteriorate due to the frequency characteristics of the cable. Since the drive signal is a pulse signal,
If the waveform deteriorates during transmission, the imaging device will not be driven accurately.

The present invention has been made in order to cope with the above-mentioned circumstances, and its purpose is to provide an endoscope apparatus in which a drive circuit for the image pickup means is provided separately from an endoscope having the image pickup means. The purpose of this invention is to correct waveform deterioration of a drive signal being transmitted through a transmission cable within an endoscope with a simple configuration.

[Means to solve the problem]

An endoscope device according to the present invention includes a solid-state image sensor provided at the distal end of the endoscope, a transmission cable disposed within the endoscope, and means for driving the solid-state image sensor via the transmission cable. , and means for correcting frequency characteristics of the transmission cable.

[Effect]

According to the endoscope apparatus according to the present invention, since the means for correcting the frequency characteristics of the transmission cable is provided, the transmission from the drive means to the solid-state image pickup device at the end of the endoscope via the transmission cable in the endoscope. Waveform deterioration of the drive signal can be prevented and the solid-state imaging device can be driven accurately [Embodiment] Embodiments of the endoscope apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a light source unit as a signal processing circuit in an embodiment near a connecting portion with an endoscope. A CCD (not shown) as a solid-state imaging device is built into the tip of the endoscope 10. A terminal for signal connection and a resistor 12 for scope (endoscope) identification are provided at the connection portion of the endoscope 10 with the light source unit. The resistance value of this resistor 12 differs depending on the scope, and by detecting this resistance value, the light source unit side determines the type of scope, and more specifically, the type of scope that is connected to the signal connection terminal and the location inside the endoscope. The length of the installed signal transmission cable can be identified. A control signal from a control circuit (not shown) is supplied to the CCD driver 16 via the isolation transformer 14.
The CCD driver 16 controls the CCD according to this control signal.
Generates drive pulses for driving. This drive pulse is transmitted to the endoscope 10 via a matching circuit 18.
and is supplied to the CCD via a signal transmission cable within the endoscope 10. Matching circuit 1
Specifically, 8 consists of a differential circuit, which generates a component (differential component) corresponding to the waveform deterioration of the drive pulse being transmitted due to the frequency characteristics of the signal transmission cable inside the endoscope.
This is a circuit that corrects the frequency characteristics of the transmission cable by adding this to the rising portion of the drive pulse in advance. Here, since the degree of waveform deterioration of the drive pulse varies depending on the length of the cable, the time constant of the differentiating circuit is varied by the identification signal from the scope identification circuit 26 to which the scope identification resistor 12 described above is connected. It's summery.

On the other hand, the video signal from the CCD at the tip of the endoscope 10 is input into the light source unit via the signal transmission cable and terminal, and is supplied to the video processing system via the differential amplifier 20, isolation transformer 22, and clamp circuit 24. be done. The video signal from the CCD is a discrete pulse-like signal for each pixel, and the clamp circuit 24
The signal is then clamped at a predetermined interval corresponding to the pixel interval and converted into a continuous signal. The timing generation circuit 32 that determines this clamp timing is determined by the output of a timing switching circuit 30 that is controlled by the output of the scope identification circuit 26. Specifically, the timing switching circuit 30 is a delay circuit, which delays the reference pulse supplied from the control circuit in accordance with the transmission delay time of the video signal depending on the type of scope, and supplies it to the timing generation circuit 32. be. Therefore, this delay time is also varied by the identification signal from the scope identification circuit 26.

FIG. 2 is a detailed circuit diagram of the scope identification circuit 26. This identification circuit 26 has a current source 40,
When the endoscope 10 is connected, a constant current is supplied from the current source 40 to the scope identification resistor 12. As a result, the resistance value of the scope identification resistor 12 is output as an inter-terminal voltage. Scope identification resistor 12
The inter-terminal voltage of is input to the comparator circuit 48. The comparison circuit 48 consists of seven comparators, and the voltage between the terminals of the scope identification resistor 12 is applied to the +input terminal of each comparator. The voltage at each voltage dividing point of the voltage divider 44 having seven voltage dividing points is applied as a reference voltage to the negative input terminal of each comparator of the comparison circuit 48. The seven comparators constituting the comparator circuit 48 are each weighted, and weights (bits) of 0 to 6 are assigned to the comparators in order from those to which the lowest reference voltage is applied. Therefore, the comparator circuit 48 selects between 0 bit and n depending on the voltage between the terminals of the scope identification resistor 12.
The output of the bit (0≦n≦6) becomes “1”,
The output of bits (n+1) to 6 becomes "0".

The 0-bit to 2-bit output signals of the comparator circuit 48 are supplied to the A2, A3, and A4 input terminals of the adder circuit 54, respectively. The 3-bit to 6-bit output signals of the comparator circuit 48 are sent to A1, A2, A3, and A4 of the adder circuit 52.
are respectively supplied to the input terminals. Addition circuit 52, 5
4 adds "1" to the output data of bits to 6 bits of the comparator circuit 48 and outputs the result. For example, when the output data of the comparison circuit 48 is "0001111", when "1" is added, it becomes "0010000".
In this way, since the output of the 0 bit to n bit of the comparator circuit 48 is 1, and the output of the (n+1) bit to 6 bit is "0", when "1" is added thereto, one of the Only the bit data becomes "1" and the others become "0". in this way,
The adder circuits 52 and 54 generate identification signals in which only one bit data is "1" and the others are "0" depending on the voltage between the terminals of the scope identification resistor 12. When the output data of the comparison circuit 48 is "1111111", adding "1" to it becomes "10000000", so the addition circuits 52 and 54 output the 8-bit identification signals ID1 to ID.
8 is output.

In this way, by passing a constant current from the light source unit side to the identification resistor 12 provided on the endoscope side and having a resistance value according to the scope length, and detecting the resistance value as the voltage between the terminals, a simple configuration is possible. Be able to identify the type of endoscope. Furthermore, although the identification signal is data of multiple bits, only one of the bit data is "1", so the matching circuit 1
8. The selection elements of the adjustment circuit, such as the timing switching circuit 30, can be selected as they are, simplifying the configuration of the adjustment circuit.

FIG. 3 is a diagram showing the detailed configuration of the matching circuit 18. The isolation transformer 14 is a capacitor 60
It is connected to the CCD driver 16 via. The matching circuit 18 includes relay switches S1 to S8,
It consists of differentiating circuits (CR differentiating circuits) DL1 to DL8 connected to each relay switch S1 to S8. CCD
The output of the driver 16 is the relay switch S1 to S8.
and are supplied to differentiating circuits DL1 to DL8, respectively. The time constants of the differentiating circuits DL1 to DL8 are different from each other. Relay switches S1-S8 are controlled by identification signals ID1-ID8, respectively.

As mentioned above, since only one of the bit data ID1 to ID8 of the identification signal is "1",
Only one of the relay switches S1 to S8 is turned on. For this reason, the CCD drive pulse is output through a differentiating circuit with a time constant according to the identification signals ID1 to ID8, and is differentiated with a time constant according to the length of the signal cable, resulting in waveform degradation during transmission through the signal cable. components are adjusted as pre-added waveforms. That is, the waveform of the drive pulse is degraded during transmission, and the drive pulse is adjusted so that it has the original correct waveform when supplied to the CCD.

FIG. 4 is a detailed circuit diagram of the clamp circuit 24. A video signal from the isolation transformer 22 is supplied to the video processing system via an impedance converter 68, a capacitor 70, and an impedance converter 74. Capacitor 70 and impedance converter 74
A dynamic clamp circuit 72 is connected between them. The dynamic clamp circuit 72 consists of an analog switch made of bridge-connected diodes and a self-bias transformer 76 when a pulsed bias current is passed through the analog switch. A timing pulse (clamp pulse) from the timing generation circuit 32 is supplied to this self-bias transformer 76, and the CCD
The pulsed video signal from is clamped and converted to a continuous signal.

As described above, the timing at which this clamp pulse is generated is delayed by the same amount of time as the delay time of the video signal in accordance with the scope identification signal, and the video signal is clamped so that it is not affected by delays during signal line transmission. The timing switching circuit 30 has the same configuration as the matching circuit 18, and instead of the CR differential circuit, eight one-shot multivibrators each having a different pulse width are provided. Reference pulses from the control circuit are input to these one-shot multivibrators via relay switches. Then, an output pulse signal from any one of the one-shot multivibrators is supplied to the timing signal generation circuit 32 in accordance with the identification signals ID1 to ID8, and a clamp pulse is generated in synchronization with the falling edge of the pulse signal.

As explained above, according to this embodiment, the drive pulse output from the control circuit is differentially processed, and the waveform deterioration during transmission through the signal transmission cable in the endoscope is added to the drive pulse in advance. By transmitting from the CCD, the frequency characteristics of the signal transmission cable can be corrected, driving pulses with a desired waveform can always be supplied to the CCD, and the CCD can be driven accurately. Furthermore, by controlling the clamping timing for converting the discrete video signal from the CCD into a continuous signal according to the length of the signal transmission cable, the signal can always be clamped at the correct timing.

Note that the present invention is not limited to the above-mentioned embodiments,
Various changes can be made without departing from the gist of the invention, and the details of the matching circuit 18 and clamp circuit 24 are not limited to the above example. Furthermore, a sample/hold circuit may be used instead of the clamp circuit 24 as a circuit for converting a discrete signal into a continuous signal.

〔Effect of the invention〕

As explained above, according to the endoscope apparatus according to the present invention, since the means for correcting the frequency characteristics of the transmission cable connecting the drive circuit and the imaging means is provided, the waveform of the drive signal supplied to the imaging means is degraded. It is possible to prevent this, and the imaging means can be driven accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an endoscope apparatus according to the present invention, FIG. 2 is a detailed circuit diagram of the scope identification circuit of FIG. 1, and FIG. 3 is a detailed circuit diagram of the matching circuit of FIG. Detailed Circuit Diagram FIG. 4 is a detailed circuit diagram of the clamp circuit of FIG. 10... Endoscope, 12... Scope identification resistor, 16... CCD driver, 18... Matching circuit, 24... Clamp circuit, 26... Scope identification circuit, 30... Timing switching circuit.

Claims (1)

[Scope of Claims] 1. A solid-state image sensor provided at the tip of an endoscope, a transmission cable disposed within the endoscope, and means for driving the solid-state image sensor via the transmission cable. An endoscope apparatus comprising: means for correcting the frequency characteristics of the transmission cable. 2. The endoscope apparatus according to claim 1, wherein the correction means is constituted by a differential circuit.