JP3306215B2 - 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 an electronic device in which a solid-state imaging device is provided at the end of an endoscope insertion portion, and an observed image is converted into an electric signal, transmitted to the outside, and reproduced on a monitor or the like. The present invention relates to an endoscope device.

[0002]

2. Description of the Related Art In order to reproduce a video signal transmitted from a solid-state imaging device provided at the distal end of an insertion portion of an endoscope as an image that does not give a sense of strangeness, it is necessary to perform gamma correction.

Therefore, conventionally, an output value after gamma correction corresponding to a video signal (original signal) value input to a gamma correction unit is written in a lookup table constituted by a memory, and the video signal is looked up. It is applied as an address signal of a table memory to output a corresponding gamma correction value. The signal after the correction is converted into an analog signal again, then subjected to video signal processing, and displayed on a monitor as an image (JP-A-1-178235).

[0004]

However, since the gamma correction unit not only amplifies the original signal up to the correction value, but also amplifies the noise component superimposed on the original signal, the input signal shown in FIG. As shown in FIG. 17, there is a disadvantage that the S / N ratio deteriorates in the low luminance (dark) range where the gain is particularly high with respect to the original signal.

When the non-linear processing is performed using a look-up table, for example, in FIG. 18, a lookup table is used so that data 1 to 4 whose addresses are between 0 and 1 are not written in the look-up table. Some data is not written to the table.

Therefore, in a low-brightness (dark) range where data changes greatly with respect to an address, much data is not written in the look-up table, and a quantization error peculiar to digital processing occurs at the time of gamma correction. Resulting in.

Accordingly, an object of the present invention is to provide an electronic endoscope apparatus capable of performing gamma correction of a digital video signal without deteriorating the S / N ratio and with a small quantization error.

[0008]

In order to achieve the above object, an electronic endoscope apparatus according to the present invention converts a video signal sent from a solid-state imaging device provided at the end of an endoscope insertion section into a digital signal. After the conversion into a signal, the gamma correction data written in the look-up table is read out, and the gamma correction of the video signal is performed. In addition to writing the data corresponding to the gamma correction only, a low-pass filter for reducing noise components from the signal output from the lookup table is provided, read from the lookup table and passed through the low-pass filter The gamma correction data is added to the original signal and output as a correction signal.

It is preferable that the original signal added to the data for only the gamma correction read from the look-up table does not pass through the low-pass filter.

[0010]

An embodiment will be described with reference to the drawings. FIG. 2 shows an overall configuration of an electronic endoscope apparatus according to an embodiment of the present invention. For example, the electronic endoscope apparatus is provided at an image forming position of a subject by an objective optical system 3 provided at a distal end of an insertion section 2 of the endoscope 1. Charge coupled device (C
A solid-state imaging device 4 made of CD) is arranged. 5
Is a light guide fiber bundle for transmitting illumination light for illuminating the observation range.

A connector section 6 of the endoscope 1 connected to the video processor 10 includes a drive circuit 7 for amplifying signals input to and output from the solid-state imaging device 4 and data specific to the endoscope 1. And a rewritable read-only memory (EEPROM) 8 in which information such as data is stored.

The video processor 10 also serves as an illumination light source device, and illumination light is incident on the light guide fiber bundle 5 of the endoscope 1 from a light source lamp 11.
A three-color rotating filter 12 having three color filters of red (R), green (G), and blue (B) is disposed in the middle of the incident optical path so as to rotate at a constant speed.
Illumination light of each color of red, green, and blue is sequentially incident on the light guide fiber bundle 5 with a time lag.

An output terminal of the CCD processing unit 14 connected to the driving circuit 7 of the solid-state image pickup device 4 is connected to a timing circuit 15.
Is connected to the input terminal of the video processing unit 16 via the
Sent to

The operations of the CCD processing unit 14, the timing circuit 15, and the video processing unit 16 are performed by a system control unit 17 having a central processing unit (CPU).
Are controlled in conjunction with each other. Further, the endoscope-side data is read from the EEPROM 8 connected thereto via the peripheral driver 19 connected to the system control unit 17.

FIG. 3 specifically shows the structure of the above-described CCD processing section 14 and video processing section 16. In the CCD processing unit 14, the solid-state imaging device 4
Is amplified by an amplifier 23, a video signal is extracted by a sample and hold circuit 24, converted into a digital signal by an analog / digital conversion circuit 25, and then subjected to gamma correction by a gamma correction circuit 26.

The gamma-corrected video signal is switched by the timing circuit 15 in synchronization with the driving of the solid-state imaging device 4, and sequentially corresponds to each color of red (R), green (G), and blue (B). It is stored in the frame memories 28R, 28G, 28B.

The signals stored in the frame memories 28R, 28G, 28B are simultaneously read out and converted into analog color signals by digital-to-analog conversion circuits 29R, 29G, 29B, respectively.

The three color signals are output as three primary color signals, respectively, and are also input to the NTSC encoder 30 in parallel with the three primary color signals, converted into an NTSC composite video signal and output to the monitor 18.

FIG. 1 shows the contents of the gamma correction circuit 26. The gamma correction circuit 26 reads out a noise component from a read-only memory 32 for a look-up table and a signal output from the look-up table memory 32. A low-pass filter 35 for reduction and an adding circuit 33 for adding the output signal from the low-pass filter 35 and the original signal are formed.

FIGS. 4 and 5 are graphs showing an example of data written in the look-up table memory 32. FIG. As shown in FIG. 4, the gamma correction value to be output from the gamma correction circuit 26 takes a large value with respect to the input original signal. However, the sum of the corrected data indicated by the oblique lines is much smaller than the sum of the gamma correction values.

Therefore, in this embodiment, only the gamma correction data shown in FIG. 5 is written in the look-up table memory 32. Then, the original signal is applied as an address signal of the look-up table memory 32, and the correction data corresponding to the address is read out of the look-up table memory 32,
, The data for the correction is added to the original signal and output as a gamma correction value.

The look-up table memory 32
May be written in advance, and gamma correction data suitable for the characteristics of the endoscope 1 and the characteristics of the subject may be selected and used.

The low-pass filter 35 is inserted and connected to a video signal output line near the output terminal of the look-up table memory 32, and the original signal sent to the adding circuit 33 does not pass through the low-pass filter 35.

FIGS. 6 to 8 show low-pass filter circuits for reducing the noise of digital signals. FIG. 6 shows a horizontal filter, FIG. 7 shows a vertical filter, and FIG. 8 shows a time filter.

Each of these receives a video signal input as a digital signal in a latch 351 and multiplies it by a plurality of predetermined constants k _{0 to} k ₄ in parallel. The vertical filter receives and adds and outputs each in the line memory 353, and the time filter receives and adds and outputs each in the frame memory 354 in the vertical filter.

When the low-pass filter processing is performed using an analog signal, the signal from the look-up table memory 32 is once converted into an analog signal, and the output from the low-pass filter is again converted into a digital signal by an A / D conversion circuit. And then sent to the adder circuit 33.

Next, the operation of the above embodiment will be described. Note that the original signal before being input to the look-up table memory 32, the signal of only the gamma correction sent to the low-pass filter 35 through the look-up table memory 32, passes through the low-pass filter 35. The signal sent to the adding circuit 33 indicates the gamma correction signal output from the adding circuit 33.

FIGS. 9 and 10 show the low-luminance areas (FIG. 5).
(Between O and H) of FIG. 9 shows a change in signal level (FIG. 9) and a change in waveform (FIG. 10). Between OH where the luminance is low, the gamma correction data also increases as the original signal level increases. Therefore, when a waveform such as the signal is input to the look-up table memory 32, the data for the gamma correction is amplified and becomes a waveform as shown in FIG.

When the gamma correction signal output from the look-up table memory 32 is passed through a low-pass filter 35, low-pass processing is performed to reduce noise,
It becomes a state like. As described above, the output signal from the look-up table memory 32 is supplied to the low-pass filter 35.
Thus, data that has not been written to the memory 32, such as “3” shown in FIG. 13, is processed as if it were output from the memory 32.

When the gamma correction component signal and the original signal are added by the adder circuit 33, a gamma correction output as shown below is obtained, and the noise component is reduced by the low-pass effect.

As described above, by providing the low-pass filter 35 on the output line of the look-up table memory 32, the noise can be smoothed as shown in FIG. it can.

When the original signal is added by the adder circuit 33, a delay element is added to the original signal transmission line sent to the adder circuit 33 in order to adjust the delay time by the look-up table memory 32 and the low-pass filter 35. May be interposed.

FIGS. 11 and 12 show a change in signal level (FIG. 11) in a high luminance area (between H and L in FIG. 5).
And changes in the waveform (FIG. 12). H- with high brightness
Between L, as the original signal level increases, the data for gamma correction decreases. Therefore, when such a signal is input to the look-up table memory 32, the gamma correction data output from the look-up table memory 32 decreases as shown in FIG. Then, when the signal is passed through the low-pass filter 35, low-pass processing is performed to reduce noise, and a state as shown in FIG.

The addition circuit 33 adds the gamma correction component signal that has passed through the low-pass filter 35 and the original signal, and
The gamma correction output is as follows, and an enhancement effect in which the outline is emphasized appears. Also in this case, the addition circuit 33
A lookup table memory 32 and a low-pass filter 35 are inserted through a delay element in the original signal transmission path sent to the
May be adjusted with the delay time.

As described above, noise is reduced in a low luminance area, and contour enhancement is performed in a high luminance area. If one of a plurality of types of gamma correction data can be selected, the noise removal area and the enhancement area can be used as needed.

The present invention is not limited to the above embodiment. For example, as shown in FIG. 15, the gamma correction circuits 26R, 26G and 26B are connected to the video processing section 16
May be connected to the output terminals of the respective color frame memories 28R, 28G, and 28B to independently perform gamma correction on each of the red, green, and blue color signals. The configuration and operation of each of the gamma correction circuits 26R, 26G, and 26B in this case are the same as those in the first embodiment.

[0037]

According to the present invention, when a video signal is output from a look-up table for reading out only data for the gamma correction, a noise component is reduced by a low-pass filter, and a signal in a dark video portion is gamma corrected. In this case, amplification of noise components is suppressed, and a good S / N ratio can be obtained.

Moreover, values not written in the look-up table can be output as gamma correction data, and quantization errors in digital gamma correction at low signal levels can be greatly suppressed.

Then, by adding the original signal that does not pass through the low-pass filter to the data for only the gamma correction,
Smoothing of the original signal waveform by the low-pass filter can be prevented, and a signal with higher precision can be output.

Further, the outline is emphasized in a bright image portion, and each of the effects of gamma correction, noise reduction, and enhancement can be realized by one circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a gamma correction circuit according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an electronic endoscope apparatus according to an embodiment of the present invention.

FIG. 3 is a circuit block diagram of an embodiment of the present invention.

FIG. 4 is an explanatory diagram of gamma correction data according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of gamma correction data according to the embodiment of the present invention.

FIG. 6 is a circuit diagram of a low-pass filter according to an embodiment of the present invention.

FIG. 7 is a circuit diagram of a low-pass filter according to an embodiment of the present invention.

FIG. 8 is a circuit diagram of a low-pass filter according to an embodiment of the present invention.

FIG. 9 is a diagram showing a change in signal level in a low luminance region according to the embodiment of the present invention.

FIG. 10 is a diagram illustrating a change in a signal waveform in a low luminance region according to the embodiment of the present invention.

FIG. 11 is a diagram illustrating a change in signal level in a high-luminance region according to the example of the present invention.

FIG. 12 is a diagram showing a change in a signal waveform in a high luminance region according to the embodiment of the present invention.

FIG. 13 is an explanatory diagram of output characteristics of the embodiment of the present invention.

FIG. 14 is an explanatory diagram of output characteristics of the embodiment of the present invention.

FIG. 15 is a circuit block diagram of a second embodiment of the present invention.

FIG. 16 is a diagram illustrating characteristics of digital gamma correction.

FIG. 17 is a diagram illustrating characteristics of digital gamma correction.

FIG. 18 is a diagram illustrating characteristics of digital gamma correction.

[Explanation of symbols]

 26 Gamma correction circuit 32 Look-up table memory 33 Adder circuit 35 Low-pass filter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-30301 (JP, A) JP-A-4-373361 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 1/00-1/32 H04N 5/202

Claims (1)

(57) [Claims] 1. A video signal sent from a solid-state imaging device provided at the end of an endoscope insertion section is converted into a digital signal, and then gamma correction data written in a look-up table is read out to convert the video signal into a digital signal. In an electronic endoscope apparatus configured to perform gamma correction of a signal, data of only a gamma correction corresponding to an input original signal is written in the look-up table and output from the look-up table. Providing a low-pass filter to reduce noise components from the signal,
The gamma correction data read from the look-up table and passed through the low-pass filter is stored in the low-pass filter .
An electronic endoscope apparatus which adds to an original signal that has not passed through a pass filter and outputs the result as a correction signal.