JPH0771205B2 - Imaging device - Google Patents

Description

The present invention relates to a camera head having a solid-state image sensor, a signal for generating a drive pulse to the solid-state image sensor, and a signal for processing a video signal from the solid-state image sensor. The present invention relates to an imaging device in which a processing unit is configured as a separate body, and a solid-state imaging device and a signal processing unit are connected via a cable.

[Conventional technology]

As such an image pickup device, there is an electronic scope in which a solid-state image pickup device such as a charge-coupled device (CCD) is built in the tip of an endoscope insertion portion to pick up an image inside a body cavity or inside a thin tubular member. Here, the signal processing unit is usually provided in the light source device as a separate body from the endoscope body.

The output signal of the solid-state image sensor is transmitted to the signal processing unit via the signal line in the endoscope, where the clamp, the sample &
Signal processing such as hold is performed to generate a video signal of the subject.

Here, the drive pulse generator is provided on the signal processing unit side in order to reduce the size of the distal end of the endoscope insertion unit as the camera head. In this case, the drive pulse is supplied to the solid-state imaging device via the cable (coaxial cable), but the high frequency component is attenuated during the transmission. Therefore, it is necessary to supply the drive pulse to the solid-state image sensor through a circuit for compensating for this attenuation in advance, that is, a frequency correction circuit that emphasizes the high frequency component of the drive pulse.

Since endoscopes have various lengths depending on the type of object, there are various lengths of cables that supply this drive pulse to the solid-state image sensor. Therefore, in order to connect a plurality of endoscopes to the same light source device (signal processing unit) in common and drive them with the same drive pulse, it is necessary to detect the cable length and perform frequency correction according to this. There is.

As a conventional example for detecting the cable length, Japanese Patent Publication No. 61-2957.
There is publication No. 4. Here, a plurality of frequency correction circuits corresponding to the cable lengths of a plurality of camera heads that are expected to be connected are provided in the camera controller, and any one frequency correction circuit is provided according to the identified cable length. You have selected. Here, a constant current is passed through an arbitrary signal line in a cable connecting the camera head and the camera controller, the voltage effect is detected, and the voltage effect of each of the plurality of camera heads expected to be connected is detected. The length of the cable is identified by comparing the detected voltage with a plurality of reference voltages corresponding to. Then, the frequency correction circuit corresponding to the identified cable length is selected by the selection switch to perform frequency correction according to the cable length.

[Problems to be solved by the invention]

In this conventional example, the cable length to be detected is limited in advance, and frequency correction is performed only for these finite cable lengths. Therefore, the frequency cannot be corrected for any cable length longer than that.

This invention has been made to deal with the above-mentioned circumstances,
The purpose is to compensate the deterioration of the high-frequency characteristics of the drive pulse during the transmission of the cable, even if the camera head with the cable of any length is connected to the drive means in the image pickup device in which the camera head and the drive means are separate bodies. An object of the present invention is to provide an imaging device that can be used without adjustment and that can properly supply a drive pulse to a solid-state imaging device in a camera head.

[Means for solving problems]

In the image pickup apparatus according to the present invention, the solid-state image pickup element 22 and the drive unit 12 that generates a drive pulse for the solid-state image pickup element 22 are connected by a cable
And the DC component of the drive pulse supplied to the solid-state image sensor 22 via the cable 26, or the transmission timing of the single pulse transmitted to and received from the solid-state image sensor 22 via the cable 26. Control voltage generators 44, 54 that output a control signal according to the time difference from the reception timing, and correction circuits 36, 38, 42 that correct the frequency characteristics, amplitude, and DC bias of the drive pulse according to the control signal are provided. .

[Action]

According to the image pickup device of the present invention, by generating a control signal according to the cable length and adjusting the correction amount of the correction circuit for correcting the frequency characteristic, the amplitude, and the DC bias of the drive pulse in accordance with the control signal, any length can be obtained. Even if a camera head having a cable is connected, the drive pulse can always be optimally compensated according to the cable length, and the drive pulse can be correctly supplied to the solid-state imaging device in the camera head.

〔Example〕

An embodiment of an image pickup apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the first embodiment.
The image pickup device includes a camera head 10, a signal processing device 12, and a display device 14.

The camera head 10 is a charge-coupled device (CC) as a solid-state imaging device that captures an optical image incident through the imaging lens 20.
D) 22, a detection circuit 24 described later, and a cable line 26 connecting the CCD 22 and the signal processing device.

CCD2 supplied to the signal processing device 12 via the cable line 26
The output of 2 is input to the signal processing circuit 30. Signal processing circuit 3
When 0, signal processing such as clamp, sample & hold is performed on the output of CCD22. The timing of signal processing is synchronized with the drive pulse of CCD22. Therefore, the output of the drive pulse generator 32 is supplied to the signal processing circuit 30.

On the other hand, the output of the drive pulse generator 32 is supplied to the amplitude correction gain amplifier 38 and the frequency correction gain amplifier 36 via the differentiating circuit 34. The differentiating circuit 34 extracts the high frequency component of the output drive pulse of the drive pulse generator 32. Frequency correction gain amplifier 36, amplitude correction gain amplifier
The output of 38 is supplied to the adder 40, and the output of the adder 40 is supplied to the CCD 22 via the DC bias correction circuit 42. The output of the DC bias correction circuit 42 is CCD2 via the cable line 26.
Supplied to 2.

The drive pulse output from the DC bias correction circuit 42 and supplied to the CCD 22 via the cable line 26 is input to the detection circuit 24. The output of the detection circuit 24 is supplied to the signal processing device 12 via the cable 26 and input to the control voltage converter 44. The control voltage converter 44 outputs the output of the detection circuit 24 and the reference voltage re
With the difference in f as the control voltage, the frequency correction gain amplifier 36,
It is supplied to the amplitude correction gain amplifier 38 and the DC bias correction circuit 42. The control voltage-gain characteristics of the frequency correction gain amplifier 36 and the amplitude correction gain amplifier 38, and the control voltage-DC bias characteristics of the DC bias correction circuit 42 are preset.

The operation of the first embodiment will be described. The DC component of the drive pulse to the CCD 22 is detected by the detection circuit 24 in the camera head 10. This DC component decreases due to the voltage drop of the cable line 26 as the length of the cable line 26 increases. This DC component output from the detection circuit 24 is operated by the control voltage converter 44 in the signal processing device 12 to calculate the difference from the reference voltage ref, and the difference voltage is obtained as the control voltage. The control voltage converter 44 generates a control voltage such that the difference between the output of the detection circuit 24 and the reference voltage ref becomes zero. That is, when the cable length is long and the DC voltage output from the detection circuit 24 is small, a large control voltage is generated. Conversely, when the cable length is short and the output voltage of the detection circuit 24 is large, it is small. Generates control voltage.

The output control voltage of the control voltage converter 44 is supplied to the frequency correction gain amplifier 36, the amplitude correction gain amplifier 38, and the DC bias correction circuit 42.

The amplitude correction gain amplifier 38 adjusts the amplitude of the drive pulse according to this control voltage. The amplitude of the drive pulse transmitted to the CCD 22 becomes smaller as the cable length becomes longer. In order to correct this, the amplitude correction gain amplifier 38 increases the amplitude of the drive pulse as the control voltage increases (the cable length increases). As a result, the amplitude of the drive pulse does not decrease even when the cable length increases, and is always kept optimum.

The high frequency component of the drive pulse output from the differentiating circuit 34 is frequency-corrected by the frequency correction gain amplifier 36 according to the control voltage, and the drive pulse transmitted to the CCD 22 via the cable line 26 is attenuated. The high frequency characteristics of are deteriorated. The influence of this deterioration also increases as the length of the cable wire 26 increases. To correct this,
The frequency correction gain amplifier 36 increases the high frequency component of the drive pulse output from the differentiating circuit 34 as the control voltage increases (the cable length increases). As a result, the frequency characteristic of the drive pulse (particularly, the high frequency characteristic) is always maintained constant without deterioration even when the cable length becomes long.

The outputs of the frequency correction gain amplifier 36 and the amplitude correction gain amplifier 38 are added by the adder 40, and as a result, the drive pulse with the adjusted amplitude and frequency characteristics is input to the DC bias correction circuit 42. The DC bias correction circuit 42 adjusts the DC bias of the drive pulse according to the control voltage. The DC component of the drive pulse decreases as the cable length increases. To correct this, the DC bias correction circuit 42 increases the DC bias of the drive pulse as the control voltage increases (the cable length increases). As a result, the DC component of the drive pulse does not decrease even when the cable length increases, and is always kept optimum.

After that, when the DC component of the drive pulse output from the detection circuit 24 matches the reference voltage ref, the frequency correction gain amplifier 3
6, amplitude correction gain amplifier 38, DC bias correction circuit 42
Control voltage (output of control voltage converter 44) becomes constant,
The high-frequency correction amount, amplitude correction amount, and DC bias correction amount of the drive pulse are set to optimum values according to the cable length.

2 (a) to (e) show this state,
The figure (a) is the output of the drive pulse generator 32, the figure (b) is the output of the differentiating circuit 34, the figure (c) is the output of the adder 40, the figure (d) is the input of the detection circuit 24, The figure (e) is the output of the detection circuit 24.

As described above, according to the first embodiment, the cable length can be detected by detecting the DC component of the drive pulse supplied from the signal processing device to the camera head via the cable line. By correcting the DC bias, the amplitude, and the frequency characteristic of the drive pulse, an imaging device capable of supplying the optimum drive pulse to a camera head of any cable length is provided.

FIG. 3 is a block diagram of the second embodiment. The second embodiment is an embodiment relating to a modification of the cable length detection, and the drive pulse correction is the same as that of the first embodiment. First
The same parts as those in the embodiment are designated by the same reference numerals. Signal processor
24 includes a detection pulse generation circuit 50, the output of which is supplied to the CCD 22 via the drive pulse transmission line in the cable line 26. A pulse detection circuit 52 is also connected to the drive pulse transmission line, and when the CCD 22 and the signal processing device 12 are not matched, the detection pulse reflected by the CCD 22 is detected by the pulse detection circuit 52. The output of the pulse detection circuit 52 is supplied to the memory 56 via the voltage conversion circuit 54. The output of the memory 56 is supplied to the frequency correction gain amplifier 36, the amplitude correction gain amplifier 38, and the DC bias correction circuit 42. Other configurations are the same as those in the first embodiment.

The operation of the second embodiment will be described. When it is detected that the camera head 10 is connected to the signal processing tail device 12, or when the power is turned on, the detection pulse generation circuit 50 generates a detection pulse consisting of a single pulse having a constant width, and together with the drive pulse. Supplied to CCD22.

If the CCD 22 in the camera head 10 is not matched with the signal processing device 12, this detection pulse is CC
It is reflected by D22 and sent back to the signal processing device 12 side. When there is a match, the detection pulse is not reflected by the CCD 22.

The time difference between the generation of the detection pulse and the reception of the reflected pulse depends on the length of the cable. This time difference is detected by the pulse detection circuit 52, and the time difference is converted into a voltage by the voltage conversion circuit 54. Therefore, the output voltage of the voltage conversion circuit 54 changes according to the cable length. The voltage conversion circuit 54 outputs a higher voltage as the cable length is longer and the time difference is larger. The output voltage of the voltage conversion circuit 54 is stored in the memory 56,
The stored voltage controls the frequency correction gain amplifier 36, the amplitude correction gain amplifier 38, and the DC bias correction circuit 42 as in the first embodiment.

As in the first embodiment, the longer the cable length, the higher the output voltage of the voltage conversion circuit 54. Therefore, the frequency correction gain amplifier 36 increases the high frequency component, the amplitude correction gain amplifier 38 amplifies the amplitude, and the DC voltage is increased. The bias correction circuit 42 also increases the DC bias. However, the correction amounts of the output voltage vs. frequency correction gain amplifier 36, the amplitude correction gain amplifier 38, and the DC bias correction circuit 42 of the memory 56 are set in advance.

The present invention is not limited to the above-described embodiments, but can be variously modified without departing from the gist of the invention. In the description, the camera head has a built-in cable line, but the camera head and the cable line may be separate bodies. Further, the image pickup apparatus may be applied to any field, not limited to the field of endoscope.

〔The invention's effect〕

As described above, according to the present invention, in the image pickup apparatus in which the camera head and the signal processing apparatus are separate bodies, a control voltage is generated according to the cable length, and the correction amount of the correction circuit is changed according to the control voltage. By doing so, it is possible to provide an imaging device in which the signal processing device can accurately supply the drive pulse to a camera head having any cable length without providing a correction circuit for each cable length.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an image pickup device according to the present invention, FIGS. 2 (a) to 2 (e) are signal waveform diagrams of respective portions showing the operation of the first embodiment, and FIG. FIG. 6 is a block diagram showing a configuration of a second embodiment of an image pickup device according to the present invention. 10 …… Camera head 12 …… Signal processor 24 …… Detection circuit 26 …… Cable line 32 …… Drive pulse generator 34 …… Differentiation circuit 36 …… Frequency correction gain amplifier 38 …… Amplitude correction gain amplifier 42 …… DC bias correction circuit 44 ... Control voltage converter

Claims (1)

[Claims] 1. An image pickup device comprising: a solid-state image sensor; a signal processing device including a drive pulse generator that generates a drive pulse for the solid-state image sensor; and a cable connecting the solid-state image sensor and the signal processing device. In the device, the signal processing device includes a detection unit that detects a change in the transmission signal due to the length of the cable, and the signal processing device receives the output of the detection unit and generates a control signal that is proportional to the length of the cable. And a variable gain amplifier whose gain characteristic with respect to the control signal is preset, the drive pulse generated by the drive pulse generator is input, and the amplitude of the drive pulse is corrected by the control signal and output. The correction means, a differentiation circuit that differentiates the drive pulse generated by the drive pulse generator and outputs a differential signal, and the differential signal is input. A high-frequency component correcting unit that includes a variable gain amplifier in which a gain characteristic with respect to the control signal is set in advance, corrects the amplitude of the differential signal by the control signal, and outputs the output of the amplitude correcting unit and a high-frequency component correcting unit. And a bias circuit in which the magnitude of the DC signal to be superimposed on the input signal is set in advance for the control signal, and the output signal of the adding means is input to determine the DC bias component. DC bias correcting means for correcting, and supplying the drive pulse corrected by the amplitude correcting means, the high frequency component correcting means, and the DC bias correcting means to the solid-state imaging device via the cable. An imaging device characterized by.