JP3207229B2 - Signal transmission processing circuit of electronic endoscope 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 signal transmission processing circuit of an electronic endoscope apparatus, and more particularly to a video signal transmission processing circuit in an electronic endoscope apparatus in which a patient circuit is connected to an output circuit by an isolation device. About.

[0002]

2. Description of the Related Art An electronic endoscope apparatus for observing the inside of a body cavity such as a digestive tract by using a CCD (Charge Coupled Device) which is a solid-state image pickup device provided at a distal end portion is well known. In this case, an image of the inside of the body to be observed picked up by the CCD is displayed on a monitor, and diagnosis and various treatments are performed while observing the image displayed on the monitor.

[0005] FIG. 5 shows a schematic configuration of a conventional electronic endoscope apparatus. As shown, an external endoscope 2 is connected to an external processor device 1. The CCD 3, which is a solid-state image sensor, is provided at the distal end of the insertion section. On the other hand, in the external processor device 1, a CCD driver 4 and a signal processing circuit 5 for amplifying video signals and the like are provided as patient circuits. It is connected to the. As this output circuit, A /
D (analog-digital) converter 7, frame memory 8,
A D / A (digital / analog) converter 9, a control circuit 10, and the like are provided.

Accordingly, when the CCD 3 is driven by the control circuit 10 and the CCD driver 4, the video signal obtained by the imaging of the CCD 3 is subjected to a process process corresponding to the color display by the signal processing circuit 5. . Thereafter, the video signal is input to the A / D converter 7 via the pulse transformer 6, and the digital video signal is stored in the frame memory 8. Then, the video signal stored in the frame memory 8 is converted into an analog signal by the D / A converter 9 and thereafter output to a monitor (not shown). The image picked up by the CCD 3 is displayed on the monitor. Image is displayed in color.

[0005] In the above, the pulse transformer 6 is provided to electrically shut off the patient circuit and the output circuit, and to maintain safety when the electronic endoscope 2 is applied to the patient. That is, the dielectric breakdown voltage of the pulse transformer 6 itself maintains a dielectric breakdown voltage of 3 to 4 kV or more between the two, and
This ensures electrical safety for patients and the like.

[0006]

However, the conventional signal transmission processing circuit of the electronic endoscope apparatus has a problem that sag is generated in a wide-band video signal due to the frequency characteristic of the pulse transformer 6 as the isolation device. there were. FIG. 6 shows the frequency characteristics of the pulse transformer 6. In the pulse transformer 6, the frequency range of about 0 Hz to 10 Hz near DC (direct current),
The gain is not constant in the region above MHz (this region can be neglected), and the video signal is output in a totally warped state in the vertical period as shown in FIG. Therefore,
The video signal is disturbed while being transmitted through the pulse transformer 6,
Good image formation is hindered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to form a feedback control loop including a pulse transformer so as to prevent the occurrence of sag when transmitting an isolation device. Another object of the present invention is to provide a signal transmission processing circuit of an electronic endoscope apparatus that can obtain a good video signal.

In order to achieve the above object, the present invention provides a pulse transformer which is an isolation device for transmitting a video signal from a patient circuit on an electronic endoscope side to an output circuit side, and an output from the pulse transformer. A sample and hold circuit for sampling and holding the reference level of the video signal, an isolation device for returning the sampled and held signal to the patient circuit side, and a video signal by feeding back the sample and hold signal returned to the patient circuit side And a control circuit configured to control so as to eliminate the sag.

[0009]

According to the above arrangement, the video signal output from the CCD and processed is transmitted through the pulse transformer, and then the reference level is sampled and held. This sample and hold voltage is referred to by, for example, an operational amplifier. The voltage is compared with the voltage, and the difference signal is output as a sag correction control signal. This sag correction control signal is input to the mixing circuit as a control circuit on the patient circuit side via the isolation device, and this control signal is added to the video signal, whereby the sag is eliminated and the signal is stabilized. A video signal is obtained.

[0010]

FIG. 1 shows a configuration of a signal transmission processing circuit of an electronic endoscope apparatus according to an embodiment, that is, a signal transmission processing circuit of an isolation device. The pulse transformer 12 as a device is provided for each of a plurality of video signals to be transmitted. On the patient circuit side electrically disconnected from the output circuit by the pulse transformer 12, a mixer 13 as a control circuit and an amplifier 14 are provided connected to the input terminal A.

On the other hand, on the output circuit side, an output amplifier 15 is connected in front of the output terminal B, and a sample-and-hold circuit 16 and a differential amplification type as a part of a control circuit are provided so as to receive the output of the output amplifier. An operational amplifier 17 is provided, and a sampling and holding circuit 16 samples and holds a reference level of the video signal.
Is given. A resistor R1 is connected to the negative terminal of the operational amplifier 17, a resistor R2 and a capacitor C1 are connected to each other, and a reference voltage Vref is applied to the positive terminal of the operational amplifier 17. The sampled and held signal voltage is compared with the reference voltage Vref, and a voltage signal having the difference is output. The output of the operational amplifier 17 is returned to the patient circuit via another isolation device 18 and is fed back to the mixer 13. Any of a photocoupler and a pulse transformer may be used as the isolation device 18.

Next, the operation according to the configuration of FIG. 1 will be described with reference to FIG.
It will be described based on. FIG. 2A shows a video signal when a sag occurs when the video signal input to the input terminal A on the patient circuit side in FIG. 1 is transmitted through the pulse transformer 12. The signal is input to the sample and hold circuit 16 via the output amplifier 15. In the sample and hold circuit 16, a reference level (black level-signal of an optical black portion) of the video signal is extracted by the sampling pulse CPs of FIG. 2B, and the voltage is held. This sample and hold voltage signal is shown in FIG.
As shown in (c), the state and degree of the sag are detected by the sample hold processing.

The sample and hold circuit 16
Is input to the negative terminal of the operational amplifier 17 and compared with the reference voltage Vref applied to the positive terminal. When the sample-hold voltage is higher than the reference voltage Vref, the negative difference A voltage signal is output, and if it is smaller, a positive difference voltage signal is output. This comparison output is converted into a gentle signal and output.
The sag correction control signal shown in FIG. The output of the operational amplifier 17 is returned to the patient circuit via the isolation device 18, and the sag correction control signal having passed through the isolation device 18 is as shown in FIG.

The sag correction control signal is supplied to the mixer 1
3 and mixed by the mixer 13 with the video signal input to the input terminal A, whereby the signal shown in FIG. 2 (f) is obtained. In this mixed video signal, the sag state of the video signal in which the sag of FIG. 2A has occurred is inverted, and the sag is transmitted as shown in FIG. A canceled video signal can be obtained. In the above description, when the isolation device 18 is a pulse transformer, it is considered that a new sag is generated in the sag correction control signal, but the sag itself generated in the sag correction control signal is also eliminated by the control loop. Become.

Next, the overall configuration of an actual electronic endoscope device incorporating the above-described signal transmission processing circuit will be described with reference to FIGS. As shown in FIG. 3, a processing unit 23 is connected to the external processor device 1 via a connector 22, and the electronic endoscope 2 is connected to the processing unit 23 integrally or by a connector. A CCD 3 is connected to a distal end of the electronic endoscope 2 and a light guide 24 for emitting observation light from the distal end is provided. In the embodiment, the CCD driver 4 and the first signal processing circuit 25 are provided in the processing unit 23 (or in the operation unit of the electronic endoscope).

FIG. 4 shows a detailed circuit of the first signal processing circuit 25 including the CCD driver 4. The first signal processing circuit 25 includes a correlated double sampling (CDS). -Correlated Double Sampling), an automatic gain control unit (AGC) 27, a process processing unit 28 that performs clamping, matrix processing, gamma correction, blanking, and the like, and a timing generator that supplies timing pulses to each unit including the CCD driver 4. The output of the CCD 3 is input to the automatic gain control unit 27. Further, a microcomputer 30 and an interface 31 are provided for efficiently performing each processing in the process processing unit 28. Therefore, according to the CCD driver 4 and the first signal processing circuit 25 provided in the processing unit 23, the driving of the CCD 3 is controlled by the CCD driver 4, and the video signal in the body to be observed obtained by the CCD 3 is applied to the video signal. On the other hand, the first signal processing circuit 25 performs image processing up to the preceding stage of the memory described later.

A signal transmission processing circuit 33 including the above-described pulse transformer shown in FIG. 1 is provided in the external processor device 1. The signal transmission processing circuit 33 includes, for example, the first signal processing circuit 25 The RGB video signals are transmitted via the first group of pulse transformers 12 provided respectively. Then, the signal transmission processing circuit 33
Is connected to a frame memory 35 via an A / D converter 34. The frame memory 35 has a D / A converter 36
The second signal processing circuit 37 is connected via the. And the output processing for outputting to a monitor is performed by the second signal processing circuit 37.

Further, a second group of isolation devices 38 and a third group of isolation devices 39 are provided in the external processor device 1, and the second group of isolation devices 38 are provided with a timing pulse generation circuit 4.
0 is connected to the third group of isolation devices 39
Is connected to an operation unit (control panel) 41.
The timing pulse generation circuit 40 outputs a timing pulse to each of the components, and outputs a synchronization signal (C-SYNC) and a blanking signal (C-SYNC) to the electronic endoscope 2 via the second group of isolation devices 38. C-BL
K), and supply pulses such as an operation control signal (4f _SC ).
On the other hand, a control signal for performing operations such as freeze, partial enlargement, electronic shutter operation, setting of γ value, and the like is supplied from the operation unit 41 to the electronic endoscope 2 via the third group of isolation devices 39. You. A transformer 43, a first power supply circuit 44, and a second power supply circuit 45 are provided. The first power supply circuit 44 is connected to the CCD driver 4 and the first signal processing circuit 25 disposed in the electronic endoscope 2. , The second power supply circuit 45 supplies power to each processing circuit in the external processor device 1.

Further, a light source 46 optically connected to the light guide 24 in the electronic endoscope 2 is provided, and a light source power supply 47 is connected to the light source 46. The light source 46 is controlled by a light source control unit 48. For example, in the case of a frame sequential method, an RGB filter is driven to output RGB light sequentially.

According to the above configuration, the light output from the light source 46 under the control of the light amount control unit 48 is transmitted to the electronic endoscope 2.
The light is transmitted through the inside by a light guide 24, whereby the observation light is emitted from the distal end portion into the body to be observed. Then,
The CCD 3 driven and controlled by the CCD driver 4 captures the image of the object to be observed illuminated by the above-described observation light.
A video signal is supplied from the CD 3 to the first signal processing circuit 25. In the first signal processing circuit 25, predetermined processing such as amplification, clamping, γ correction, blanking, and the like is performed on the video signal.

The video signal thus input is
The signal is supplied to the signal transmission processing circuit 33 of FIG. 1 and transmitted to the output circuit side via the pulse transformer 12 as described above. Is electrically disconnected. Then, the output of the output amplifier 15 on the output circuit side [FIG.
(A)] is supplied to the sample hold circuit 16 and is sampled and held by the sampling pulse CPs. Next, the sample-hold voltage is compared with the reference voltage Vref by the operational amplifier 17, and a sag correction control signal [FIG. 2 (d)] is output. The sag correction control signal is transmitted through the isolation device 18. To the patient circuit side and input to the mixer 13. Then, in the mixer 13, the sag correction control signal is mixed with the video signal [FIG. 2 (f)], and the mixed signal is transmitted through the pulse transformer 12, so that the sag-free video signal [FIG. )] Is obtained.

As described above, the video signal transmitted between the patient circuit and the output circuit is once stored in the frame memory 35 via the A / D converter 34, and when read out thereafter, the D / D The signal is input to the second signal processing circuit 37 via the A converter 36, and the RGB signal, the Y / C signal, and the like are output from the second signal processing circuit 37 to the monitor. Note that a synchronization signal is output from the timing pulse generation circuit 40 to the monitor. In this way, an image of the inside of the body to be observed is displayed in color on the monitor.

In the above embodiment, the operational amplifier 17, the mixer 13, and the amplifier 14 are provided as the control circuit. However, other circuits can be applied as the control circuit. For example, instead of the mixer 13, the amplifier 14, A sag correction control signal output from the operational amplifier 17 can be fed back to the variable gain amplifier to eliminate sag of the video signal.

[0024]

As described above, according to the present invention,
When transmitting between a patient circuit and an output circuit via a pulse transformer, a reference level of a video signal is sampled and held from an output of the pulse transformer to obtain a sag correction control signal, and the sag correction control signal is used as an isolation device. , A control loop for controlling by returning to the patient circuit side is provided, so that sag of the video signal can be eliminated satisfactorily, and good transmission of the video signal in the isolation device becomes possible.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram illustrating a configuration of a signal transmission processing circuit of an electronic endoscope apparatus according to an embodiment of the present invention.

FIG. 2 is a waveform chart showing the operation of each component of the embodiment of FIG.

FIG. 3 is a circuit block diagram illustrating an overall configuration of the electronic endoscope apparatus according to the embodiment.

FIG. 4 is a circuit block diagram showing a configuration inside a first signal processing circuit in the circuit of FIG. 3;

FIG. 5 is a circuit block diagram illustrating a schematic configuration of a conventional electronic endoscope apparatus.

FIG. 6 is a graph showing frequency characteristics of a pulse transformer.

FIG. 7 is a waveform diagram showing a video signal in which sag has occurred.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... External processor apparatus, 2 ... Electronic endoscope, 3 ... CCD, 6, 18, 38, 39 ... Isolation device, 12 ... Pulse transformer, 13 ... Mixing part, 14, 15 ... Amplifier, 16 ... Sample hold circuit , 17 ... an operational amplifier, 25 ... a first signal processing circuit, 33 ... a signal transmission processing circuit.

Claims (1)

(57) [Claims] 1. A pulse transformer which is an isolation device for transmitting a video signal from a patient circuit on an electronic endoscope side to an output circuit side, and a sample for sampling and holding a reference level of a video signal from an output of the pulse transformer. A hold circuit, an isolation device for returning the sampled and held signal to the patient circuit side, and control for returning the sample and hold signal returned to the patient circuit side so as to eliminate sag of the video signal A signal transmission processing circuit for an electronic endoscope apparatus, comprising: a control loop including a circuit.