JPH06103933B2 - TV camera device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television camera device, and more particularly to a television camera device such as an endoscope image pickup device having a solid-state image pickup element built in at its tip end that may come into contact with a human body.

[0002]

2. Description of the Related Art As a conventional technique of such a television camera device, there is an endoscope camera as described in JP-A-55-54933. In this endoscope camera, a solid-state image pickup device such as a CCD is built in the tip of the endoscope, an optical image obtained by an image pickup lens is picked up by the CCD, and an image pickup signal is displayed on an external display monitor. It

In recent years, for such an endoscopic camera,
Considering safety, there is a possibility of contact with the power source and the human body C
Standards are being set for the breakdown voltage with respect to the CD and the leakage current. For example, if AC100V is used as the power source,
It is considered that the withstand voltage is 4 KV and the leakage current is 10 μA. In consideration of such safety standards, it is conceivable to insert an isolation transformer into the signal line between the CCD at the tip of the endoscope and the power supply in the external light source device to divide the signal line. However, it is necessary to avoid the deterioration of the image quality of the image due to this.
Even if the isolation transformer is inexpensive, it surely meets the standards for withstand voltage and leakage current. However, the isolation transformer has drawbacks that it is difficult to transmit low-frequency signals and that the band is relatively narrow. If the isolation transformer is designed to have a wide band, the transmission efficiency will be poor and the cost will be high. By the way, since the output signal from the CCD has a wide frequency band from the direct current component to several MHz, the transmission of the video signal itself is disturbed and the image quality is deteriorated by simply inserting the isolation transformer.

As described above, in the conventional endoscopic camera, if the signal line between the power source and the portion that may come into contact with the human body is divided to satisfy the standards of withstand voltage and leakage current, the image quality is reduced. However, there was a problem in that

[0005]

SUMMARY OF THE INVENTION The present invention has been made to cope with the above-mentioned circumstances, and an object thereof is to electrically connect a camera unit that comes into contact with a human body and an external power supply unit with a cheap and reliable method. It is an object of the present invention to provide a television camera device that can be isolated from each other and can keep the withstand voltage and the leakage current between the camera unit and the power supply unit within a safe range.

[0006]

A television camera device according to the present invention comprises a television camera section having a solid-state image pickup device, a video process means for processing an output signal from the television camera section, a television camera section and a video process means. And an isolation transformer section which is provided between the solid-state image sensor and has a pass band of a drive pulse frequency, and a clamp circuit which clamps an output signal from the isolation transformer section with a clamp pulse synchronized with the drive pulse of the solid-state image sensor. It is characterized by including.

[0007]

According to the television camera device of the present invention, the video signal component which is a low frequency component lost by simply passing the output signal of the television camera portion through the isolation transformer portion can be reproduced by the clamp circuit. The video signal component can pass through the isolation transformer without distortion, and the inexpensive isolation transformer can reliably electrically isolate the TV camera unit and the power supply unit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a television camera device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. An imaging lens 12 is built in the tip of the endoscope 10, and an optical image of a subject formed by the imaging lens 12 is incident on an imaging surface of a solid-state imaging device (here, CCD) 14 such as CCD or MOS. . Inside the endoscope 10, a light guide 16 for guiding the illumination light emitted from an external light source device (not shown) to the tip, and a magnifying lens 18 for illumination are also provided. The output signal from the CCD 14 is amplified by the preamplifier 20 and then supplied to the primary winding of the isolation transformer 66 via the signal line. The output signal of the isolation transformer 66 is supplied to the video process circuit 32 via the impedance converter 68, the capacitor 70, and the impedance converter 74. Output signal of the impedance converter 74 (CCD 14
(The same as the output signal of 1) is subjected to processing necessary for conversion into a television signal in the video process circuit 32 and displayed on the CRT monitor 34. A dynamic clamp circuit 72 is connected between the capacitor 70 and the impedance converter 74. The dynamic clamp circuit 72 has an analog switch composed of a diode connected in bridge, and a self-bias transformer 76 for supplying a pulsed bias current to the diode. The clamp pulse synchronized with the drive pulse of the CCD 14 is supplied to the self-bias transformer 76.

The bandwidth of the isolation transformer 66 is set to the frequency band of the drive pulse (transfer clock) of the CCD 14. Therefore, if the output signal of the CCD 14 is transmitted through the isolation transformer 66 without being AM-modulated (carrier suppression modulation), the video signal component which is the low frequency component of the output signal is lost. However, in this embodiment, the lost video signal component is reproduced as follows. The output voltage of the CCD 14 normally has a waveform as shown in FIG. Here, the envelope represents the video signal. Since this video signal component is completely cut by the isolation transformer 66 and only the frequency of the drive pulse is passed through this signal, FIG.
The signal becomes as shown in (b). That is, the absolute value of the envelope is different from that before passing through the isolation transformer 66. However, by clamping with the dynamic clamp circuit 72 within the reset period using a clamp pulse as shown in FIG. 2C, a low frequency video signal component can be reproduced. This is clamped to the reference level for each pulse, and the clamp timing is the lower surface of the waveform in FIG. 2B. Since this point is the reference level, the waveform after clamping is the same as the output signal waveform of the CCD 14. Become. In principle, the frequency that can be reproduced by Nyquist's theorem is up to half the clamp frequency. Therefore, the bandwidth of the isolation transformer 66 needs to sufficiently include a frequency that is ½ of this clamp frequency.

As described above, according to this embodiment, the CCD 1
Since the output signal from 4 is transmitted to the video process circuit 32 and the CRT monitor 34 through the isolation transformer 66, the tip of the endoscope that may come into contact with the human body can be reliably electrically isolated from the power source. It is possible to keep the withstand voltage and leakage current value within the safe range. Since the video signal component, which is a low frequency component that is lost when passing through the isolation transformer 66, can be reproduced by the dynamic clamp circuit 72, the video signal component can pass through the isolation transformer section without distortion. The television camera unit and the power supply unit can be reliably electrically isolated from each other with a simple circuit configuration without providing an AM modulation circuit before the ration transformer. Further, the dynamic clamp circuit 72 is a very simple circuit and can sufficiently reproduce the video signal component.
For example, even if an attempt is made to detect the signal of FIG. 2B with a diode, only a peak value of 1/2 can be obtained. Furthermore, since the diode actually causes a loss of 0.7 V, it is not suitable for a weak video signal.

Incidentally, the isolation point for safety can be realized in the video process circuit 32. However, in that case, when trying to isolate a digital signal after A / D conversion, if the A / D converter outputs 8 bits, it is necessary to isolate eight signal lines. Further, even if isolation is performed in the analog section before the A / D converter, it is necessary to isolate the clamp signal and the sample hold pulse signal for interphase double sampling.
The number of signal lines that must be isolated increases. Further, in the case of isolation in the video process circuit 32, the circuit scale electrically connected to the human body becomes large. Therefore, it becomes difficult to spatially isolate the outside of the housing or the like. Therefore, we want to minimize the circuit scale that is electrically connected to the human body. The circuit scale can be reduced by connecting the isolation transformer 26 between the CCD 14 and the video process circuit 32 as in the first embodiment. The present invention is not limited to the above-mentioned embodiments, but can be implemented with various modifications. For example,
The signal from the CCD 14 may be taken out via the S / H circuit and LPF.

[0012]

As described above, according to the present invention, the camera section that comes into contact with the human body and the external power supply section can be inexpensively and reliably electrically isolated from each other, and the breakdown voltage between the camera section and the power supply section can be reduced. Provided is a television camera device capable of keeping a leak current value within a safe range.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a television camera device according to the present invention.

FIG. 2 is a signal waveform diagram illustrating the operation of this embodiment.

[Explanation of symbols]

10 ... Endoscope, 14 ... CCD, 20 ... Preamplifier, 32
... Video process circuit, 34 ... CRT monitor, 66 ... Isolation transformer, 68, 74 ... Impedance converter, 72 ... Dynamic clamp circuit.

Claims (1)

[Claims] 1. A television camera unit having a solid-state imaging device, a video process unit for processing an output signal from the television camera unit, and a solid-state imaging device provided between the television camera unit and the video process unit. An isolation transformer unit having a frequency of a drive pulse as a pass band, and a clamp circuit that clamps an output signal from the isolation transformer unit with a clamp pulse synchronized with a drive pulse of the solid-state image sensor. TV camera device.