JPH08131401A - Electronic endoscopic device - Google Patents

Abstract

PURPOSE: To provide an electronic endoscope device capable of reproducing an image with high quality even when dispersion between picture elements exists in the amplitude of a signal of saturation level outputted from each picture element of a solid-state image pickup element. CONSTITUTION: This device is provided with saturation level amplitude correction circuits 21, 22 and 23 to correct the signal level of each picture element so as to arrange the amplitude of saturation level of the signal of each picture element at the minimum level required for the input dynamic range of an analog/digital conversion circuit 18 before an image pickup signal is inputted to the analog/digital conversion circuit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus in which a solid-state image pickup device for converting an observed image into an electric signal is provided at the tip of an endoscope insertion portion.

[0002]

2. Description of the Related Art FIG. 10 shows a conventional electronic endoscope apparatus in which an analog signal output from a solid-state image pickup device (not shown) arranged at the tip of an endoscope insertion portion is a preamplifier 51. After being amplified to an appropriate level by, the high pass component and the like are cut by the low pass filter 52.

Next, in the sample hold circuit 53, the output signal from each pixel of the solid-state image pickup device is sampled to extract the image pickup signal, and the signal is output to the next amplifier until the signal exceeds the input dynamic range of the analog-digital conversion circuit 56. After being amplified by 54, the clamp circuit 5
At 5, waveform shaping is performed to align the DC levels on one side.

Then, the signal is converted into a digital signal in an analog-digital conversion circuit 56 and then sent to a next image processing circuit (not shown) to generate a video signal for reproducing a color image.

[0005]

In the circuit described above, the amplitude of the saturation level of the signal output from each pixel of the solid-state image pickup device varies from pixel to pixel.

That is, FIG. 11 exemplifies an input signal and an output signal to the sample hold circuit 53 in the case where the saturation level signal is sequentially output from each pixel of the solid-state image pickup device, and the variation in the amplitude is amplified. It is amplified at 54 and appears as it is. V _AD is an analog-digital conversion circuit 5
The dynamic range of 6 inputs, Av is the gain of the amplifier 54.

As described above, since the variation in the saturation level amplitude of the signal output from each pixel between pixels appears at the input / output of the sample hold circuit 53 as it is, if the input level to the sample hold circuit 53 has a dynamic range. If there is a pixel signal below, that pixel is displayed as a black dot in the image, and the image quality is significantly impaired.

However, if the amplification factor of the amplifier 54 is increased in order to avoid such a phenomenon, image noise becomes conspicuous and the image quality as a whole is deteriorated this time.

Therefore, the present invention provides an electronic endoscope apparatus capable of reproducing a high quality image even if the amplitude of the saturation level signal output from each pixel of the solid-state image pickup device varies among the pixels. The purpose is to provide.

[0010]

In order to achieve the above object, the electronic endoscope apparatus of the present invention sample-holds an analog signal output from a solid-state image pickup device arranged at the tip of an endoscope insertion portion. In an electronic endoscope apparatus in which an imaging signal is extracted by sampling with a circuit, amplified, and then converted into a digital signal by an analog-digital conversion circuit, before inputting the imaging signal to the analog-digital conversion circuit In addition, saturation level amplitude correction for correcting the signal level of each pixel so that the magnitude of the amplitude of the saturation level of the signal of each pixel is aligned with the minimum level required for the input dynamic range of the analog-digital conversion circuit. It is characterized in that a circuit is provided.

[0011]

Embodiments will be described with reference to the drawings. FIG. 2 is a schematic diagram showing the overall configuration of the electronic endoscope apparatus. For example, a charge-coupled device (CC) built in the tip of the insertion portion of the endoscope 1 is used.
The endoscope observation image is captured by the solid-state image sensor 2 including D), and the signal output from the solid-state image sensor 2 is
Sent to the video processor 3 connected to the endoscope 1,
It is input to the CCD process circuit 10 in the video processor 3.

FIG. 1 shows a CCD process circuit 10, in which an analog signal output from the solid-state image sensor 2 is
First, after being amplified to an appropriate level by the preamplifier 11, high frequency components and the like are cut by the low pass filter 12.

Next, in the sample hold circuit 13, the output signal from each pixel of the solid-state image pickup device 2 is sampled to extract the image pickup signal, and the signal is output until it exceeds the input dynamic range of the main analog-digital conversion circuit 18. After being amplified by the amplifier 14, the waveform is shaped by the clamp circuit 15 so that the DC levels on one side are made uniform. Up to this point, the circuit is the same as the conventional circuit shown in FIG.

The signal output from the clamp circuit 15 is a video signal in which the amplitude of the saturation level of the signal output from each pixel varies, as shown in FIG.

A high-precision amplifier (hereinafter referred to as a "multiplier") capable of controlling the amplification degree with high precision by 8-bit digital data with respect to an analog signal input to the output end of the clamp circuit 15 16 are connected, and a correction analog-digital conversion circuit 21 that outputs, for example, 8-bit digital data is branched and connected.

In this embodiment, as a preparation for using the endoscope, a very bright subject is imaged by the solid-state image sensor 2 to saturate the output signals from all the pixels, and the signal is corrected. Input into the analog-to-digital conversion circuit 21 for use.

Then, the saturation level signals of all the pixels of the solid-state image pickup device 2 are stored in the next image memory 22. Such a preparatory operation is performed by, for example, the video processor 3
It is assumed that the operation is performed only when the switch 24 arranged on the operation panel is pressed.

In the normal observation state after the saturation level signals of all the pixels are stored in the image memory 22, the timing circuit 25 synchronizes with the driving of the solid-state image pickup device 2 and the saturation corresponding to each pixel. The level data is output from the image memory 22. Therefore, in that state, the function of the correction analog-digital conversion circuit 21 is no longer used.

The data output from the image memory 22 is input to the correction coefficient storage memory 23 in which the correction coefficient is stored. The correction coefficient is, for example, a coefficient for correcting all the data V1 to V4 input from the image memory 22 as shown in FIG. 4 so as to be aligned with the dynamic range V _AD of the input of the main analog-digital conversion circuit 18. is there.

In this way, the correction coefficient corresponding to each pixel is output from the correction coefficient storage memory 23 and the multiplier 16
And the amplification factor of the multiplier 16 is controlled for each pixel. As a result, the signal amplitude of the saturation level of each pixel in FIG. 1 output from the multiplier 16 becomes the dynamic range V _AD of the input of the main analog-digital conversion circuit 18 in all pixels as shown in FIG. Aligned.

Next, the signal output from the multiplier 16 is subjected to waveform shaping by the clamp circuit 17 so that the DC level on one side is made uniform, and then converted into a digital signal by the main analog-digital conversion circuit 18 to convert a video signal. It is output to the image processing circuit for generation.

FIG. 6 is a block diagram for explaining the circuit portion for performing the above-mentioned signal correction in more detail. The 2.0 Vpp signal (Vi) output from the clamp circuit 15 is shown in FIG.
n) is input to the attenuator (ATT) 27 and is multiplied by 0.5 in order to reduce the maximum value of the dynamic range V _AD2 of the correction analog-digital conversion circuit 21 to 2.0 V, and then the correction analog-digital conversion circuit. 21 is input. Then, the correction analog-digital conversion circuit 21
After being converted into bit digital data (D1), it is temporarily stored in the image memory 22.

The data (D1) output from the image memory 22 is input to the correction coefficient storage memory 23 in which the correction coefficient is stored, and the 8-bit data (D2) output from the correction coefficient storage memory 23 causes the multiplier 16 to output data. The amplification factor Av is controlled. The relationship between D1 and D2 is D2 = 64 × 256 / D1 (Equation 1), as shown by the characteristic curve in FIG.

Here, the dynamic range V _AD2 of the correction analog-digital conversion circuit 27 in FIG.
When 0V, D1 = 256, Vin becomes 4.0V and D
1 = 256. Therefore, Vin / 4 = D1 / 2
The expression 56 (Expression 2) is established. Further, the amplification factor Av of the multiplier 16 is Av = D2 / 256 when D2 is 256 at the maximum.
(Equation 3)

From these equations 1 to 3, Av = 1 / Vi
Therefore, the output from the multiplier 16 is always 1V. Therefore, the signal is doubled by the amplifier 28 to be 2.0 V which is V _AD , and the clamp circuit 17
And input to the main analog-to-digital conversion circuit 18.

In this way, the signal amplitude when each pixel of the solid-state image pickup device 2 is at the saturation level is aligned with the dynamic range V _{AD of the} input of the main analog-digital conversion circuit 18 in all the pixels, so that black dots appear on the screen. Moreover, it is possible to reproduce a high quality image without noise deterioration.

8 and 9 show a second embodiment of the present invention, FIG. 8 is a schematic diagram showing the whole structure, and FIG. 9 is a circuit block diagram. In the above-described first embodiment, the switch 24 is operated each time the endoscope 1 to be used is replaced,
It is necessary to take time and effort to acquire the amplitude data of the saturation level of the signal output from each pixel of the solid-state image sensor 2.

Therefore, in this embodiment, at the stage of manufacturing the endoscope 1, amplitude data of the saturation level of the signal output from each pixel of the solid-state image pickup device 2 is obtained, and the data and the correction characteristic shown in FIG. 7 are obtained. The data obtained by multiplying and is stored in the read-only memory (ROM) 31, and the ROM
The endoscope 31 is built in the endoscope 1.

When the endoscope 1 is connected to the video processor 3, the data stored in the ROM 31 in the endoscope 1 is read and stored in the random access memory (RAM) 32 in the CCD process circuit 10. The data is transferred, the timing circuit 33 synchronizes with the driving of the solid-state imaging device 2, and the amplification factor of the multiplier 16 is controlled in pixel units as in the first embodiment.

By doing so, the signal amplitude of the saturation level of each pixel is mainly measured in all pixels without the trouble of acquiring the saturation level data of each pixel each time the endoscope 1 to be used is replaced. The dynamic range V _AD of the analog-digital conversion circuit 18 can be aligned.

[0031]

According to the present invention, before the image pickup signal from the solid-state image pickup device is input to the analog-digital conversion circuit,
Since the amplitude of the saturation level of the signal of each pixel can be adjusted to the minimum level required for the input dynamic range of the analog-digital conversion circuit, the amplitude of the saturation level signal output from each pixel of the solid-state image sensor Even if there are variations among pixels, it is possible to reproduce an image of good quality without black spots on the screen and without deterioration due to noise.

[Brief description of drawings]

FIG. 1 is a block diagram of a CCD process circuit according to a first embodiment.

FIG. 2 is a schematic diagram showing the overall configuration of the first embodiment.

FIG. 3 is a diagram showing a signal waveform of the first embodiment.

FIG. 4 is a diagram showing a signal waveform of the first embodiment.

FIG. 5 is a diagram showing a signal waveform of the first embodiment.

FIG. 6 is a partial detailed block diagram of a CCD process circuit according to the first embodiment.

FIG. 7 is a correction characteristic diagram of the first embodiment.

FIG. 8 is a schematic diagram showing the overall configuration of a second embodiment.

FIG. 9 is a circuit block diagram of a second embodiment.

FIG. 10 is a block diagram of a CCD process circuit of a conventional example.

FIG. 11 is a diagram showing a signal waveform of a conventional example.

[Explanation of symbols]

 2 solid-state image sensor 18 main analog-digital conversion circuit 21 correction analog-digital conversion circuit 22 image memory 23 correction coefficient storage memory 24 switch

Claims (1)

[Claims] 1. An analog signal output from a solid-state image pickup device arranged at the tip of an endoscope insertion portion is sampled by a sample hold circuit to extract an image pickup signal, which is then amplified by an analog-digital conversion circuit. In an electronic endoscope apparatus adapted to convert into a digital signal, before inputting the image pickup signal to the analog-digital conversion circuit, the amplitude of the saturation level of the signal of each pixel is input to the analog-digital conversion circuit. An electronic endoscope apparatus characterized in that a saturation level amplitude correction circuit for correcting the signal level of each pixel is provided so as to be adjusted to the minimum level required for the dynamic range.