JP3420930B2 - Electronic endoscope signal processing circuit - 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 processing circuit of an electronic endoscope, and more particularly to an electronic device for forming a moving image by a conventional pixel mixed read method and reading all pixels accumulated in an image pickup device to form a still image. The present invention relates to a configuration for adjusting an exposure amount when selecting a still image in an endoscope.

[0002]

2. Description of the Related Art In an electronic endoscope apparatus, for example, a CCD (Charge Coupled Device) is used as a solid-state image pickup element. In this CCD, an image is read by reading out charges accumulated in a pixel unit by a photoelectric conversion element. It is configured to obtain a signal (video signal). And
For example, in the simultaneous electronic endoscope apparatus, a color filter is arranged on a pixel-by-pixel basis on the upper surface of the CCD, whereby a color image is obtained.

FIG. 8 shows the arrangement of the above color filters. As shown in the figure, on the image pickup surface of the CCD 1, for example, pixels of even numbers of Mg (magenta) and Cy (cyan), G (green) and Ye (yellow) pixels are arranged on odd lines. In this CCD 1, accumulated charges (pixel signals) in pixel units are passed through these color filters.
Is obtained.

According to the conventional color-difference line-sequential mixed read-out method, the accumulated charges of pixels on the upper and lower lines are added and mixed and read. For example, in the first exposure, the mixed signal of 0 line and 1 line, the mixed signal of 2 line and 3 line,
A video signal of an odd field such as ... is read, and a mixed signal of 1 line and 2 line at the time of the second exposure, a mixed signal of 3 line and 4 line, ... of an even field such as ... The video signal is read. Therefore, the mixed signal of the two lines of the CCD 1 becomes the signal of one line of the field image, and the data of one field of odd number or even number is obtained by one exposure.

FIG. 9 shows the operation of the signal read from the CCD 1. In the electronic endoscope apparatus, as shown in FIG. 1A, 1/60 seconds (vertical synchronization period).
An odd field and an even field are formed based on the O (Odd) / E (Even) signal (field signal) for each. Therefore, as shown in FIG. 6B, signal accumulation is performed by the accumulation (exposure) time T of the electronic shutter during the 1/60 second period, and the accumulated mixed signal is generated in the next 1/60 second period. Is read. As a result, as shown in FIG. 8C, an odd field signal and an even field signal are obtained. For example, the (n-1) th odd field signal is the (0 + 1) line shown on the left side of FIG. .. are mixed signals of (2 + 3) lines, (4 + 5) lines, and the n-th even field signal is a mixed signal of (1 + 2) lines, (3 + 4) lines ... Shown on the right side of FIG.

The odd-numbered field signal and the even-numbered field signal are interlaced and scanned to form a one-frame image, which is displayed as a moving image on the monitor. Further, in the endoscope apparatus, a freeze switch is arranged on the operation unit, and when the freeze switch is pressed, a still image at that time is formed and displayed.

[0007]

However, in the simultaneous electronic endoscope apparatus, as shown in FIG. 9C, the odd field image and the even field image for forming one frame image are used. Between and 1/60
If there is a time lag of seconds and the endoscope itself shakes or the subject moves during this time, there is a problem that the image quality (resolution, color misregistration, etc.) decreases when displaying a still image. .
That is, in the case of a moving image, it is often better to faithfully reproduce the movement of a subject or the like by the pixel mixture reading in the CCD 1 described above, but in the case of a still image, the resolution is lowered.

Therefore, the applicant has decided to adopt a all-pixel reading method in which a predetermined light-shielding period is provided and data of all pixels obtained by one exposure is read out by utilizing this light-shielding period. There is a problem that the exposure amount in the period for which all pixels are read becomes insufficient due to a delay in mechanical (gear, etc.) response of the light shielding plate that sets the light shielding period. That is,
Since the complete shading state is required during the shading period for reading data, the shading plate is operated slightly before the shading period in consideration of its response time. Insufficient amount of light occurs in all the operations.

The present invention has been made in view of the above problems, and an object of the present invention is to read all pixels in an electronic endoscope capable of obtaining a high-quality still image and a moving image in which motion is faithfully reproduced.
An object of the present invention is to provide a signal processing circuit of an electronic endoscope capable of satisfactorily compensating for a shortage of light amount due to a response delay of a light shielding mechanism for a bending method .

[0010]

In order to achieve the above object, the present invention provides an image pickup device for forming a moving image by mixing and outputting pixel signals accumulated in the image pickup device between upper and lower lines (horizontal lines). output during pixel-mixing reading scheme, a single exposure out read the signals of all pixels stored in the image pickup device, the electronic endoscope equipped with reading all pixels which form a still picture
Signal processing circuit , when selecting the all pixel readout method
In order to read all pixel signals in
Equipped with a shading plate that shades the field period as a shading period
Well, considering the response delay time of this shading plate,
The light-shielding means to be operated before the light-shielding period, and
Per image signal output from the image pickup device based on the pixel reading method, characterized by comprising an amplifier, the amplifying the amount corresponding to insufficient light due to the response delay of the light-shielding operation by the light shielding means. Further, a digital signal processing circuit for converting an image signal output from the image pickup device into a digital signal and performing various kinds of digital processing including gamma correction is provided, and the amplifier is provided in an analog signal processing area before the digital signal processing circuit. Can be provided. Furthermore, the amplifier can be provided in the analog signal processing area after the digital signal processing circuit that performs various signal processing.
In this case, it is preferable to provide the gamma correction circuit after the amplifier.

With the above arrangement, when the freeze switch is pressed, the all-pixel reading method is selected and a still image is formed. For example, 1/60 of the predetermined (first)
The charge accumulated by the exposure (exposure time is arbitrary) within the second period (vertical synchronization period) is the second period (1/60
Second), the odd lines of the image pickup device (CCD) are read out (stored in a predetermined memory) and stored in a predetermined memory,
During the third period (at the time of the next exposure), the remaining even lines are read out and are also stored in the predetermined memory. Then, the light source light in the second period is blocked by the light blocking means so that the even lines can be read.

That is, if the charge of the next exposure is accumulated as in the conventional case during the second period in which the accumulated charges of the odd-numbered lines are sequentially read out, the remaining even-numbered lines cannot be read out.
Therefore, in the present invention, the light output in the second period is eliminated, and the accumulated charges in the even lines are read in the third period. As a result, it is possible to read out signals for all pixels of the image sensor obtained by one exposure.

Next, the video signal of, for example, the odd line initially stored in the above memory is further stored in the phase adjustment memory and delayed by 1/60 seconds, and thereafter, the odd line is converted into the odd line by the mixing circuit. Pixel mixing processing is performed with the data of even lines. That is, this pixel mixing process is
As a result, a signal equivalent to that of the pixel mixture read method at the time of image sensor output when the signal is output from the image sensor is formed, but the pixel mixture is performed based on the data obtained by one exposure. This is distinguished from the pixel mixed read method at the time of element output.

Then, odd and even field signals are formed by this pixel mixture signal, and a still picture is displayed based on these video signals. Therefore, a still image is formed on the basis of the signals of all pixels obtained by one exposure, and becomes a high quality image. On the other hand, in the normal state when the freeze switch is not pressed, the pixel mixture reading method at the time of outputting the image sensor is selected, and the pixels of the two horizontal lines read from the image sensor are mixed and output as in the conventional case. It is possible to obtain a moving image that faithfully reproduces the movement of.

However, in the above-described light-shielding operation for a still image, as described above, for example, the mechanical response delay of the light-shielding plate causes a shortage of light amount during the exposure period of still image formation. Therefore, in the present invention, the amplifier amplifies the image signal output from the image pickup device in an amount corresponding to the insufficient light amount described above, thereby obtaining an appropriate light amount and displaying a still image with good brightness. It will be.

[0016]

FIG. 1 shows a circuit configuration of an electronic endoscope apparatus as a first example of the embodiment, and this electronic endoscope apparatus includes a scope (electronic endoscope) 10. , And is connected to a processor device having an image processing circuit or a light source device. The scope 10 is provided with a CCD 12 having a color filter similar to that described in FIG. 8 at the tip thereof, and a light guide 15 for guiding the light of the light source lamp 14 to the tip. . Further, a freeze switch 16 for displaying a still image is provided on the operation unit of the scope 10.

A CCD drive circuit 18 for driving the CCD 12 and having an electronic shutter function is connected to the CCD 12, and the timing generator 1 is connected to the drive circuit 18.
9. A microcomputer (microcomputer) 20 for performing various controls including writing and reading of memory is connected, and the operation signal of the freeze switch 16 is input to this microcomputer 20. The CCD drive circuit 18 inputs a timing signal based on the control of the microcomputer 20, and performs drive control of a CCD output pixel mixed read method for a moving image and an all pixel read method for a still image.

For example, in the case of this all-pixel reading method,
The CCD drive circuit 18 supplies two kinds of pulses for reading the accumulated data of all the pixels accumulated in the CCD 12 in one exposure into an odd line and an even line with a temporal shift. Based on this, control is performed to separately and sequentially read the signals of the odd lines and the signals of the even lines from the CCD 12. In the CCD mixed pixel readout method, one type of readout pulse is applied to each line.

An amplifier 21 which amplifies an image signal in order to make up for a shortage of light quantity when a still image is selected is provided at the subsequent stage of the CCD 12, and as the amplifier 21, an automatic gain circuit (AGC) normally provided is provided. ) Etc. can be used. That is, the amplification factor Y which is higher than the normal amplification factor Y by (1 + α) in, for example, two field periods (vertical synchronization period) after the freeze switch 16 is pressed.
The still image signal (voltage) is amplified by (1 + α). Thus, the shortage of the light amount caused by the response delay of the light blocking plate 36 for the next light blocking period, that is, the shortage of the exposure amount for the still image immediately before the light blocking period is resolved.

The amplifier 21 has a first memory 23 for storing the image data of the odd lines and a second memory for storing the image data of the even lines for reading all pixels through the A / D converter 22. Memory 24, the first memory 23
Data is stored as it is, and the read timing is 1 /
Third memory 2 for phase adjustment to delay by 60 seconds
5. A still image mixing circuit 26 is provided. That is, CCD
The all-pixel signal obtained in 12 is temporarily stored in the memories 23 and 24 in a state of being divided into the data of the odd line and the data of the even line, but the odd line data of the first memory 23 is 1 / By delaying for 60 seconds, the second
It has the same phase as the even line data stored in the memory 24.

As a result, both image data can be read at the same time, and the mixing circuit 26 in the next stage adds and mixes the pixel data of the odd lines of the third memory 25 and the pixel data of the even lines of the second memory 24. (Still image pixel mixing processing) can be performed. Therefore, in the case of a still image, the mixing circuit 26 forms a pixel mixing signal equivalent to that of the conventional color difference line sequential mixing reading method.

FIG. 2 shows the contents of still image data formed by the circuits from the CCD 12 to the mixing circuit 26 described above. As shown in FIG. 1A, the CCD 12 is provided with horizontal lines from line 0 to line N corresponding to the number of scanning lines, and pixel data of this horizontal line is transferred to a transfer line and read out. To be done. Then, the data of the odd-numbered lines (1, 3, 5 ... Lines) of the CCD 12 is stored in the first memory 23 (and the third memory 25) of FIG. 7B, and the even-numbered lines (2, 4, 6 ... Lines). Data is stored in the second memory 24 of FIG.

The data in these memories 25 and 24 are output by the mixing circuit 26 as shown in FIGS.
Pixels are mixed with each other, and as shown in FIG. 3D, 0 line + 1 line, 2 line + 3 line, 4 line
Line + 5 lines ... Addition operation data is odd (Odd)
It is output as field data. In addition, in the state where the read line in FIG.
(Reading from position 1), pixel mixing is performed between the lines shown in FIG. 2B, and as shown in FIG.
2 lines, 3 lines + 4 lines, 5 lines + 6 lines ...
The addition operation data of is output as even field data. In this example, odd lines of the CCD 12 are ODD, even lines are EVEN, odd fields of the interlaced scan target are Odd, and even lines are Ev.
Distinguish as en.

In FIG. 1, an image switching circuit 28 for switching between a moving image and a still image is provided at the subsequent stage of the mixing circuit 26. In this image switching circuit 28, the A / D for forming a moving image is formed at its a terminal. The output of the converter 22 is supplied through the L line, and the output of the mixing circuit 26 is given to the other b terminal. When the freeze switch 16 is pressed, the microcomputer 20 controls the a terminal to the b terminal. Can be switched to the terminal. This image switching circuit 28 has a DV
A P (digital video processor) 29 is connected to the DVP 29. The DVP 29 performs color signal processing in the same pixel-mixing read-out method as in the related art and performs various kinds of processing including gamma correction. A signal is formed.

In the subsequent stage of the DVP 29, the fourth memory 3 for storing the data of the odd field and the even field.
0 and the fifth memory 31, a switching circuit 32 for switching between the fourth memory 30 side terminal and the fifth memory 31 side terminal, D /
An A converter 33 is provided. For example, in the case of a still image, the fourth memory 30 stores the odd field data obtained by converting the data of FIG. 2D into a color difference signal, and the fifth memory 31 stores the data of FIG. Even field data converted into a signal or the like is stored.

On the other hand, in the light source section for supplying light to the light guide 15 arranged in the scope 10, a diaphragm 35 for adjusting the amount of emitted light and a light shield are provided between the light source lamp 14 and the incident end of the light guide 15. A plate (shading means) 36 is arranged. The light blocking plate 36 is configured to rotate, for example, a semi-circular plate, and a drive circuit 38 is connected to rotate the light blocking plate 36. The light shielding plate 36 of the example is
Based on the field O / E signal (every 1/60 seconds), the light is blocked for a predetermined 1/60 second after the freeze switch 16 is pressed.

The diaphragm control circuit 3 is provided in the diaphragm 35.
9. A lamp drive circuit 40 is connected to the lamp 14, and the diaphragm control circuit 39 drives the diaphragm 35 based on the brightness signal obtained by the DVP 29 to adjust the amount of light emitted from the lamp 14.

The first example has the above construction, and its operation will be described with reference to FIGS. As shown in FIG. 3B, the field O (Odd) / E (Eve)
As the n) signal, a timing signal for forming a 1-field image in 1/60 seconds is used as in the conventional case. In the normal state, it is set to execute the moving image processing, that is, the pixel mixture read-out method at the time of CCD output, and the light shielding plate 36 of FIG.
The light from is emitted from the distal end portion into the body to be observed through the light guide 15.

By this light irradiation, an image of the inside of the body to be observed is captured by the CCD 12 at the tip end, and charges corresponding to this image light are accumulated. The accumulated charge is read by adding pixels in the upper and lower lines by a drive pulse from the CCD drive circuit 18, and the pixel mixing signal described in FIG. 8 is output as in the conventional case. Then, this moving image signal is sent from the A / D converter 22 through the through line L to the image switching circuit 28.
The video signal is supplied to the DVP 29 through the terminal a of the image switching circuit 28. This DV
The operation after P29 is similar to the conventional one, and the fourth and fifth operations are performed.
A moving image is displayed on the monitor based on the odd and even field signals stored in the memories 30 and 31.

On the other hand, when the freeze switch 16 of the scope 10 shown in FIG. 1 is pressed, the image switching circuit 28 is switched to the terminal b side by the microcomputer 20, and the pixel mixture reading system is changed to the all-pixel reading system for still images. Can be switched to. For example, as shown in FIG. 3A, the trigger Tr1 (or Tr2) generated by the freeze switch 16 is used.
Is given, the next rising edge of the O / E signal (t
1) About 1/60 seconds from before (details will be described later),
The light blocking plate 36 blocks the optical path [Fig.
(C)], meanwhile, as shown in FIG. 3D, the output light from the light source unit is blocked. Therefore, the image data from which all the pixels are read becomes the electric charges accumulated in the CCD 12 by the light output Lt in the period of 1/60 second, which is one before the light-shielded period.

That is, FIG. 3 (E) shows the odd-numbered read pulse P1 shown in FIG. 2 (B), and FIG. 3 (F) shows FIG. 2 (C).
The read pulse P2 for the even lines shown in FIG. 2 is C by the read pulse P1 without the pulse at t2 and the read pulse P2 without the pulse at t1 as shown in the figure.
Odd (ODD) line data and even (EV) from CD12
EN) line data is sequentially read. Therefore, the reading of the odd lines is performed during the light-shielding period (t1 to t2), and the reading of the even lines is performed during the next period (t2 to t3).

The operation of the electronic shutter is shown in FIG. 3G, in which the accumulated charge in the rising period of the pulse is swept out and the accumulated charge in the falling period is read out. Therefore, strictly speaking, the above-mentioned still image data (accumulated electric charge) is obtained by exposing the g1 portion after the electric charges are swept out, and the electric charges of all the pixels are read out by the CCD drive circuit 18. . Further, in the light-shielding period (t1 to t2) after the above g1, the sweeping is omitted.

[0033] In the shading period of the the total light shielding state complete, it is necessary to ensure that charges in CCD12 are not accumulated, the control of the light-shielding plate shown in FIG. 4 is performed for it. FIG. 4 is a part of FIG. 3 (for B, C, D, G)
In the light-shielding plate control pulse of FIG. 6C, a pulse that falls early by the time ta is taken into consideration in consideration of the mechanical response delay time ta of the drive unit (gear or the like) of the light-shielding plate 36. Form. Then, when the light shielding plate 36 is driven, the light emitted from the light source unit is quadratically attenuated in the response period ta as shown in FIG. Will be moved to. Therefore, in the light output Lt for the still image, a loss of the light amount La occurs, and
As shown in, even in the exposure of the g1 portion obtained in the actual charge storage time Ts, as compared with the case of the moving image,
The light amount becomes insufficient by the light amount La.

Therefore, in the first example, the amplifier 21 performs the signal amplification corresponding to the above-mentioned insufficient light amount, and this state is shown in FIG. As shown in FIG. 5 (G), in the amplifier 21, assuming that the gain at the time of moving image is Y, the still image signal (voltage) is gained with the gain of Y (1 + α) in the period of two fields from t1 to t3. ) Is amplified. That is, the above α is the ratio of the shortage to the required light amount, and by amplifying this ratio α, it is possible to supplement the insufficient light amount La in the light output Lt [FIG. 4 (D)] during the still image formation. Become.

Then, the CCD 1 is controlled by such exposure control.
Based on the control of the microcomputer 20, the odd line data obtained from No. 2 is written in the first memory 23 as shown in FIG. 5 (H), and the even line data is given as the second line data in FIG. 5 (I).
It is written in the memory 24. Next, FIG. 5 (J), (K)
As shown in FIG. 3, the odd line data of the first memory 23 and the even line data of the second memory 24 are read twice, and the odd line data is read in the third phase for 1/60 second phase adjustment. It is stored in the memory 25. Therefore, as understood from FIGS. 5K and 5L, the data of the odd line and the data of the even line are aligned in the same phase (timing).

The respective data read out from the memories 25 and 24 in this way are pixel-mixed by the mixing circuit 26. In this example, in order to enable this, FIG.
As in (M), the first memory 23 and the second memory 24 are write-protected. Then, pixel mixture conversion is performed in the same period as this [FIG. 5 (N)], and first shown in FIG. 2 (D).
The added data of 0 line + 1 line, 2 line + 3 line ... Is output and stored in the fourth memory 30 as odd field data (Odd) [FIG. 5 (O)]. Next, the addition data of 1 line + 2 lines, 3 lines + 4 lines, ... Shown in FIG. 2 (E) is output and stored in the fifth memory 31 as even (Even) field data [FIG. 5 (P )].

Thus, at the same time that the odd field data and the even field data are read, the switching circuit 32 selects the fourth memory 30 and the fifth memory 31 so that the respective field data are alternately output. . These field data are output to the monitor via the D / A converter 33, and an image is displayed on the monitor by interlaced scanning. As a result, a still image is displayed based on all pixel data obtained during the same exposure, and an image with high image quality and optimum brightness can be obtained. Therefore, even if the endoscope itself shakes or the object to be observed moves in 1/60 seconds, it is possible to observe a clear still image with a small effect.

6 and 7 show the configuration of the signal processing circuit according to the second example. In FIG. 6, in the second example, an amplifier 45 is provided after the D / A converter 33, and a gamma correction circuit 46 is connected after the amplifier 45. That is, the same applies to the case of the first example, but when the amplifier 45 (21) compensates for the insufficient light quantity, the effect of gamma correction for reproducing a faithful color on the color TV is not diminished, so that Amplifier 4 in front of gamma correction circuit 46
It is necessary to connect 5.

According to the above configuration, as shown in FIG. 7 (P), the period (1+
The image signal is amplified with the gain of α), and
The odd field signal and the even field signal shown in (N) and (M) are multiplied by (1 + α). As a result, similarly to the first example, it is possible to supplement the insufficient light amount La and obtain a still image with good brightness.

[0040]

As described above, according to the present invention,
Forming a video pickup element pixel mix reading system at the output, in the electronic endoscope to form a still image in all <br/> pixel reading scheme, the
An amplifier for amplifying the amount of light corresponding to the insufficient light amount due to the response delay of the light shield plate operation that sets the light shield period of the all pixel readout method is provided, so that a high-quality still image and a moving image that faithfully reproduces the motion can be obtained. With the electronic endoscope ,
Execute from before the shading period to obtain a perfect shading state.
It is possible to compensate for the shortage of light amount caused by the operation of the light shielding plate, and there is an advantage that a still image with good brightness can be formed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a signal processing circuit of an electronic endoscope according to a first example of an embodiment of the present invention.

FIG. 2 is a diagram showing image data read from a CCD in FIG. 1 to a mixing circuit.

FIG. 3 is a waveform diagram showing an operation from light blocking to signal reading when forming a still image in the first example.

4 is a waveform diagram in which a part of the operation of FIG. 3 is enlarged.

FIG. 5 is an explanatory diagram showing a still image forming operation of the first example.

FIG. 6 is a block diagram showing an overall configuration of a signal processing circuit according to a second example.

FIG. 7 is an explanatory diagram showing a still image forming operation of a second example.

FIG. 8 is a diagram illustrating a configuration of a color filter in a conventional CCD and pixel mixture reading.

FIG. 9 is an explanatory diagram showing the operation of a conventional CCD.

[Explanation of symbols]

1,12 ... CCD, 10 ... Scope, 14 ... Light source lamp, 16… Freeze switch, 18 ... CCD driving circuit, 20 ... Microcomputer (control means), 21, 45 ... Amplifier, 23, 24, 25, 30, 31, ... Memory, 26 ... Mixing circuit, 28 ... Image switching circuit, 29 ... DVP, 35 ... Aperture 36 ... Light shield.

Continuation of the front page (56) References JP-A-63-82619 (JP, A) JP-A-1-191822 (JP, A) JP-A-2-193633 (JP, A) JP-A-9-90244 (JP , A) JP-A-10-85174 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) A61B 1/00

Claims (3)

(57) [Claims] 1. A pixel accumulated in an image sensorsignalUp and down
Image sensor output that mixes the output between the outputs and forms a moving image
The time pixel mixed read-out method and the above image sensor with one exposure
Accumulated signal of all pixelsReadOverhang and form a still image
Electronic endoscope with all-pixel readout methodSignal processing circuitso
ThereRead out all pixel signals when selecting the above all pixel readout method
In order to shade the next field period of the field during exposure
Equipped with a light-shielding plate that shields light between the
Considering time, move the shading plate from before the shading period.
Light-shielding means to make Based on the above all pixel readout method Output from the above image sensor
Of the generated image signal,
An amplifier that amplifies the amount corresponding to the insufficient light amount due to the response delay
When,Signal processing circuit of the electronic endoscope provided with. 2. A digital signal processing circuit for converting an image signal output from the image pickup device into a digital signal and performing various kinds of digital processing including gamma correction, and an analog signal processing area in a preceding stage of the digital signal processing circuit. The signal processing circuit for an electronic endoscope according to claim 1, wherein the amplifier is provided in the signal processing circuit. 3. The image signal is converted into a digital signal,
2. The signal processing circuit for an electronic endoscope according to claim 1, further comprising a digital signal processing circuit for performing various kinds of signal processing, wherein the amplifier is provided in an analog signal processing area at a stage subsequent to the digital signal processing circuit. .