JPH0724651B2 - Image processing method in electronic endoscope apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image processing method in an electronic endoscope apparatus for imaging in a frame sequential method.

[Conventional technology]

The field-sequential method that sequentially obtains color images corresponding to illumination light of each color from one two-dimensional sensor such as CCD is effective when multiple CCD two-dimensional sensors cannot be mounted. In recent years, medical electronic endoscopes have been developed. It is being applied to devices.

Such an electronic endoscope apparatus simultaneously converts color images sequentially captured according to illumination light via red (R), green (G), and blue (B) field memories, and outputs color images as color images. It is configured to play on a TV.

[Problems to be Solved by the Invention]

However, in an electronic endoscope apparatus that captures images in the frame-sequential method, it is necessary to make the field data of each of R, G, and B the same field in order to prevent surface flicker. Only one of the field data is read from the CCD or the two-pixel mixed data is read from the CCD at one time.

Therefore, the vertical resolution of the CCD was half that of the original CCD.

In addition, a general electronic endoscope device is a full-frame CCD (500 (H)) of 1/2 inch or 1/3 inch optical size of a general TV.
× 400 (V) = 200,000 pixels) is used, but the CCD that can be used for small diameter endoscopes such as bronchoscopes is a CCD for local observation with a size of about 2 mm square or less and the number of pixels. Is also small with tens of thousands of pixels.

Therefore, when the CCD is operated in the current system, the screen size is determined by the number of pixels, and a 2 mm square CCD has a small screen size, which is a practical problem.

The present invention has been made in view of such circumstances, and provides an image processing method in an electronic endoscope apparatus capable of improving the resolution in the vertical direction and quadrupling the screen size in area ratio. The purpose is to provide.

If the CCD has a small shape and a small number of pixels and is displayed on a monitor, the reproduced image will inevitably have a rough texture and the outline will be blurred. The present invention also aims to eliminate such drawbacks,
It is an object of the present invention to provide an image processing method in an electronic endoscope apparatus that can obtain a sharp reproduced image with a fine contour line and a clear sharpness.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention obtains a color signal of a frame sequential method from an image pickup device arranged at a distal end portion of an endoscope, A / D-converts the frame sequential color signal, and sequentially stores in a memory for each color. Along with, in the image processing method in the electronic endoscope apparatus, which is converted into a simultaneous color signal by synthesizing the frame-sequential color signals read from each memory, and a color image is reproduced by the simultaneous color signal, By transferring the odd field data and the even field data of the image pickup device within one field period, the frame sequential color signal is obtained, and the odd field data and the even field data are stored in each memory for each horizontal scanning line. Of the reproduced image obtained from the frame data and the data of It is characterized by emphasizing data processing straight edge direction was set to obtain the simultaneous type color signal after the addition to the frame data.

Further, it is characterized in that a read clock frequency for reading out the color signal from each memory is set to a half of a write clock frequency for writing the color signal into each memory.

Further, the frame data read out from the memory of any color among the memories for each color is D / A converted, and the amplitude of 1H delay frame data delayed by one horizontal scanning period is doubled. Non-delayed frame data that is only D / A converted and not delayed, and after D / A conversion 2
The data obtained by subtracting the 2H delay frame data delayed by the horizontal scanning period from the memory for each color is read by the D / A
It is characterized in that the simultaneous color signal is obtained after performing data processing for adding to the 1H delay frame data of each color delayed for one horizontal scanning period after conversion.

[Action]

According to the present invention, the odd field data and the even field data of the CCD are both read out within one field period, and the data are read from the odd field data and the even field data in the memory of the corresponding color channel for each horizontal scanning line. Since the data is alternately written as frame data, and the simultaneous color signal is obtained after the data processing for enhancing at least the vertical edge of the reproduced image obtained from the frame data is added to the frame data, The resolution in the vertical direction can be doubled as compared with the conventional method, and at least a reproduced image in which the vertical contour line is fine and clear can be obtained.

Further, by making the read clock frequency 1/2 times the write clock frequency to the memory, the screen size can be made 4 times as large as the area ratio.

Further, since the data obtained by subtracting the non-delayed frame data and the 2H delayed frame data from the doubled 1H delayed frame data is added to the 1H delayed frame data for each color, the vertical direction can be made with a simple arithmetic circuit configuration. It is possible to obtain a reproduced image in which the contour line of is strongly emphasized.

〔Example〕

Hereinafter, preferred embodiments of an image processing method in an electronic endoscope apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an electronic endoscope apparatus to which the method of the present invention is applied. Light from an illumination lamp 10 passes through a near infrared ray removing filter 12, a color filter disk 14 and a light guide 16. The subject 18 is illuminated from the tip of the endoscope. That is, the color filter disk 14 has a red filter, a green filter, and a blue filter, respectively, and is rotated by the motor 2 at a predetermined rotation speed (for example, 20 rps). As a result, the light from the illumination lamp 10 sequentially changes through the rotating color filter disk 14 in a cycle of 1/60 seconds, that is, a red (that changes in synchronization with the cycle of the VD pulse shown in FIG. 2A). It becomes illumination light of each color of R), green (G), and blue (B) (FIG. 2 (B)), and is applied to the subject 18 via the light guide 16.

An image pickup lens 22 provided at the tip of the endoscope picks up an image of a subject 18 illuminated by red, green, and blue illumination light and forms an image on a light receiving portion of a CCD 24.

The CCD 24 has, for example, a size of several mm square, and has an interline of, for example, 141 pixels in the vertical direction (V) and 100 pixels in the horizontal direction.
The CCD is driven by a drive pulse which is applied by the synchronizing signal generating circuit 26 through the CCD drive circuit 28. That is, CCD24
In the photoelectrically converted image information incident on the light receiving portion of the CCD, odd field data and even field data of the CCD 24 are sequentially interline-transferred within one field period as shown in FIG. The even field data is applied to the A / D converter 32 via the process amplifier 30.

Here, the interlaced scanning will be described in more detail below.
As shown in the figure, within one field period (16.6 mS), first, the horizontal scanning line which constitutes the odd field (0)
Minute data is transferred, and then data for horizontal scanning lines 'to' constituting the even field (E) is transferred.

In addition, the data transfer time for one horizontal scan line is set to H / 2
(≈31.75 μS), and the transfer time of data for one frame is shortened to about 4.61 mS (≈31.8 μS × 141 + 2H). In addition, 2H in the figure shows the period of the protrusion to the vertical transfer path. In this way, by increasing the transfer rate from the CCD24 and reading it, the light irradiation time is increased and the CCD24
I am trying to get the output voltage of.

Further, the horizontal transfer (write) frequency is set to 2f _SC ≈ 7.16MHz.

The A / D converter 32 converts a frame sequential color signal (analog signal of the odd field and even field) corresponding to each input illumination light into a digital signal, and outputs this digital signal to the changeover switch 34.

The change-over switch 34 changes over the input frame-sequential color signal to any one of the three memories 40, 42 and 44 and outputs it in synchronization with a timing pulse of one field period applied from the synchronizing signal generating circuit 26. Movable contact piece 34E
Are sequentially switched to the contacts 34A, 34B, 34C, 34A ... And the frame sequential color signals corresponding to the respective illumination lights are sequentially output to the memories 40 to 44.

The three memories 40 to 44 temporarily store frame data (odd field data and even field data) for each color, and writing and reading of frame data are controlled by a control signal from the memory drive circuit 48.

Next, the writing / reading control of the memory will be described.

As shown in FIGS. 2 (C) and 3, the field sequential color signals of the odd field and the even field are sequentially written in the corresponding memories, and at the same time, as shown in FIGS. 2 (D) and 4 (A). As shown in (C) to (C), the R, G, and B color signals are read and converted into the simultaneous system.

Further, as shown in FIG. 4C, when writing the odd field data and the even field data, the data of the first horizontal scanning line of the odd field, the data of the first horizontal scanning line of the even field, the odd field The data of the second horizontal scanning line, the data of the 70th horizontal scanning line of the even field, and the data of the 71th horizontal scanning line of the odd field are written in the order of the odd field and the even field alternately for each horizontal scanning line. In this way, one frame data is completed. Of course, field period on TV monitor (16.6mS, 262.
5 horizontal lines, 1H (6
3.5 μS), and the read period of one frame data is about 8.95 mS (≈63.5 μS × 141). Further, the read clock frequency f _{SC at} this time is 3.58 MHz, which is 1/2 of that at the time of writing.

Referring back to FIG. 1 again, the frame data representing the color signals read out from the memories 40, 42 and 44 as described above are set as R _0H , G _0H and B _0H , respectively, and the respective frame data R _0H , G _0H , B
_{When 0H} is delayed by 1 horizontal scanning period to be read frame data R _1H , G _1H , B _1H, and frame data G _1H is further delayed by 1 horizontal scanning period to be read frame data G _2H , read from the memory 40. The frame data R _1H is input to the D / A converter 50, the frame data G _0H read from the memory 42 is input to the D / A converter 52, the frame data G _1H is input to the D / A converter 54, Frame data G _2H is D / A
Each is input to the converter 56. Further, the frame data B _1H read from the memory 44 is input to the D / A converter 58, and converted into an analog signal by each D / A converter 50, 52, 54, 56, 58. The input frame data of each D / A converter 50, 52, 54, 56, 58 is a digital signal, and the output signal is an analog signal.The contents of each frame data are different only between digital and analog. Since they are the same, the same symbols are used for symbols such as R _1H and G _0H that represent each frame data.

Output signal G _0H of D / A converter 52, output signal G of D / A converter 54
The output signal G _2H of the _1H and D / A converter 56 is the vertical contour signal G
It is input to the vertical detail forming circuit 60 forming _E.
The vertical detail forming circuit 60 forms the vertical contour signal G _E by performing the arithmetic processing of G _E = 2 × G _1H − (G _0H + G _2H ) ... (1) from the input signals.

An example of the process of forming the vertical contour signal G _E is shown in FIG.

In FIG. 5, the frame data G _0H has a density of 0 level until time t ₁ , as shown in FIG. 5A, becomes a signal showing a deep green color with a sharp rise at time t ₁ , and continues until time t _4. It is assumed that the signal has the same density and returns to the density 0 level with a sharp fall at time t ₄ .

Since the frame data G _1H is a signal obtained by delaying the frame data G _0H by 1H, as shown in FIG.
It rises at time t _{2 one} hour after time t ₁ and starts at time t _4.
The signal will fall at time t ₅ after 1H.

Similarly, the frame data G _2H rises at time t _{3 one} hour after time t ₂ as shown in FIG.
a falling signal to the time t ₆ after 1H period from t _5.

In the vertical detail forming circuit 60, the above three pieces of frame data G _0H , G _1H , G _2H are arithmetically processed according to the equation (1) and output, so that the output vertical contour signal G _E is as shown in), from 1H period (time t ₁ immediately before the rise of the frame data G _1H until time t ₂₎ negative represents the amplitude, time from the 1H period (time t ₂ from the time of rise of the frame data G _1H Up to t ₃ ) shows positive amplitude. Similarly, the positive 1H period (from time t ₄ to time t ₅ ) immediately before the fall of the frame data G _1H indicates a positive amplitude, and the negative 1H period (from time t ₅ to time t ₆ ) immediately after the fall is negative. Shows the amplitude of.

On the other hand, the output frame data R _1H of the D / A converter 50 and the output frame data G _1H of the D / A converter 54 are input to a known horizontal detail forming circuit 62, and the horizontal contour signal H _{E is received} by a known method. Are formed and input to one input terminal of the adder 70.
The vertical contour signal G _E is applied to the other input terminal of the adder 70.
Is input and is added to the horizontal contour signal H _E by the adder 70 to output a total contour signal T _E in the horizontal and vertical directions.

The contour signal T _E is input to one input terminal of each of the adders 64, 66 and 68, and the other input terminal of each of the adders 64, 66 and 68 is
Output frame data R _IH respective D / A converter 50, the output frame data G _IH of the D / A converter 54, the output frame data B _IH of the D / A converter 58 is input.

In each adder 64, 66, 68, the input frame data R _1H , G _0H , B _1H and the contour signal T _E are added, and frame data R ′ _1H , in which vertical and horizontal contours are emphasized.
G _'1H, B' is output as _1H. When showing ignoring horizontal contour signal H _E the waveform of the frame data G _'IH As an example, becomes as FIG. 5 (E), 1 horizontal scanning line immediately before being colored green indicates a negative green component , The next horizontal scanning line is colored green more intensely than the average green level. That is, since the green component is completely removed immediately before being colored green, and immediately after being colored dark green, the contour of the green color in the vertical direction is reproduced extremely vividly.

The same operation is performed at the trailing edge of the frame data _G'1H , and one horizontal scanning line at the trailing edge shows a dark green color, and the green component of the one horizontal scanning line immediately below it is completely decolorized, resulting in a strong green color. Is displayed.

This is another frame data R _'1H, B' _1H same can, respectively red, the even blue signals to the vertical contour signal G _E
Therefore, the contour is not colored.

Output frame data R _'1H, G' of each of the adders 64, 66, 68 _IH,
B ′ _1H is input to the encoder 72, is combined with the encoder 72 into a color video signal of, for example, NTSC system, and is output as a composite color video signal.

In this way, since one frame data / one field period data is obtained from the CCD24, the vertical resolution can be doubled, and this one frame data can be converted into an odd field (70 lines), An image of 141 lines (double the image in the vertical direction) is synthesized from the even field (70 lines), and 2f _SC (7.16MH) in the horizontal direction.
By reading the data f _SC (3.58 MHz) written in z), a doubled image is obtained, which allows the screen size to be quadrupled in practical use in terms of area ratio. Further, since the data for each horizontal scanning line is alternately constituted from the odd field data and the even field data to form the frame data, and the contour is formed, the horizontal scanning line forming the contour has a high vertical density. Fine contours can be formed.

In this embodiment, the odd field data is first transferred from the CCD 24 and then the even field data is transferred, but the odd field data and the even field data may be transferred alternately.
Further, the vertical detail forming circuit 60 forms the vertical contour signal G _E by using the frame data G _0H , G _1H , and G _2H representing the green color signal. , Which is used in the highest wavelength band of, and therefore has a good S / N and a large resolution, and other red or blue color signals may be used to form the vertical contour signal.
Further, the horizontal detail forming circuit 62 does not necessarily have to be used.

〔The invention's effect〕

As described above, according to the image processing method in the electronic endoscope apparatus according to the present invention, the resolution in the vertical direction can be improved, and the screen size can be quadrupled by the area ratio. Can be applied to CCD electronic endoscopes with a small size, and it is possible to obtain reconstructed images with fine contour lines and sharpness.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic endoscope apparatus to which the method of the present invention is applied, and FIGS. 2A to 2D are timings of respective parts used for explaining FIG. A chart, FIG. 3 is a timing chart showing details of data transfer by interlaced scanning of CCD, and FIGS. 4 (A) to 4 (C) are used for explaining reading of data from the memory of FIG. 1, respectively. Timing chart, fifth
The figure is an example of a waveform diagram showing the operation of the vertical detail forming circuit of FIG. 24 …… CCD, 26 …… Synchronous circuit, 28 …… CCD drive circuit, 34 …… Changeover switch, 40,42,44 …… Memory, 48 …… Memory drive circuit, 60 …… Vertical detail forming circuit, 62… … Horizontal detail forming circuit, 64, 66, 68, 70… Adder, 72… Encoder.

Claims (3)

[Claims] 1. A color signal of a frame-sequential system is obtained from an image pickup device arranged at the tip of an endoscope, and the frame-sequential color signal is converted into an A / D signal.
In the electronic device, which is converted and sequentially stored in the memory for each color, is converted into a simultaneous color signal by synthesizing the frame sequential color signals read from each memory, and a color image is reproduced by the simultaneous color signal. In the image processing method in an endoscope apparatus, the field sequential color signal is obtained by transferring the odd field data and the even field data of the image sensor within one field period, and the odd field data and the field data are stored in each memory. The even-numbered field data is alternately written as data for each horizontal scanning line to form frame data, and data processing for emphasizing at least a vertical edge of a reproduced image obtained from the frame data is added to the frame data. Characterized by obtaining simultaneous color signals The image processing method in the daughter endoscope apparatus. 2. The electronic endoscope according to claim 1, wherein a read clock frequency for reading the color signal from each memory is set to a half of a write clock frequency for writing the color signal to each memory. Image processing method in mirror device. 3. The frame data read from a memory of any color among the memories of the respective colors is D / A converted and delayed by one horizontal scanning period, and the amplitude of 1H delayed frame data is doubled. The data obtained by subtracting the non-delayed frame data read from the memory and D / A converted but not delayed and the 2H delayed frame data delayed by 2 horizontal scanning periods after the D / A conversion are read from the memory for each color.
3. The simultaneous color signal is obtained after performing data processing of adding to 1H delay frame data of each color delayed for one horizontal scanning period after D / A conversion. Image processing method in electronic endoscope apparatus.