JPH11276432A - Electronic endoscope device to set light shielding period - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate irregularity in light quantity reduction even when a restrictor opening quantity or electronic shutter speed is different in an electronic endoscope to read all pixels by providing a light shielding period. SOLUTION: A liquid crystal shutter 23 is disposed between a restrictor blade 22 to restrict a light flux incidental from a light source lamp 14 and a light guide, and this liquid crystal shutter 23 is on-/off-controlled by a control circuit 26, so light from the lamp 14 is transmitted for a moving picture, and that light is shielded for a still picture. A response time in setting a light shielding period is extremely shortened by this, and light quantity reduction generated by the response time becomes an ignorable value. For signals for the still picture, signals for all picture elements obtained by a CCD 12 by one exposure are read utilizing the light shielding period, and a pixel mixing process is then conducted, thereby a picture image of a high picture quality and of a stable brightness can be provided.

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, and more particularly, to an electronic endoscope in which a light-shielding period is set to read out signals of all pixels stored in an image pickup device. The present invention relates to a configuration for securing an exposure amount necessary for the above.

[0002]

2. Description of the Related Art In an electronic endoscope apparatus, for example, in a CCD (Charge Coupled Device) which is a solid-state image pickup device,
An image signal (video signal) is formed by reading out the electric charge accumulated for each pixel by the photoelectric conversion element.
In the simultaneous type electronic endoscope apparatus, a color filter is arranged for each pixel on the upper surface of the CCD, thereby obtaining a color image.

FIG. 6 shows an arrangement state of the above-mentioned color filters. As shown in the figure, on the imaging surface of the CCD 1, for example, Mg (magenta),
Cy (cyan) filters and G (green) and Ye (yellow) filters are arranged on odd-numbered lines.
In the CD1, accumulated charges (pixel signals) in pixel units are obtained through these color filters.

According to the conventional mixed reading method,
The accumulated charges of the pixels on the upper and lower lines of the CCD 1 are added and mixed and read. For example, as shown on the left side of FIG. 6, a mixed signal of 0 line and 1 line is obtained for the charge accumulated in the exposure within the first 1/60 second period (vertical synchronization period).
A video signal of an odd field (Odd) such as a mixed signal of two lines and three lines,..., Is read out, and the charge accumulated by the exposure within the second 1/60 second period is shown on the right side of FIG. As shown, a mixed signal of one line and two lines, a mixed signal of three lines and four lines,..., And a video signal of an even field (Even) are read.

Accordingly, the two-line mixed signal of the CCD 1 becomes a signal of one line of the field image, and the odd field signal and the even field signal which are read out by shifting one line are alternately read every exposure within a period of 1/60 second. Is output. These odd and even field signals are interlaced and scanned to form an image of one frame, and this image is displayed as a moving image or a still image on a monitor.

[0006]

However, in the above-mentioned electronic endoscope apparatus, as described above, between the odd field signal and the even field signal for forming one frame image, 1/60 second is required. There is a time lag, and during this time, if the endoscope itself is shaken or the object to be observed moves, there is a problem that the image quality (resolution, color shift, etc.) of the still image is particularly deteriorated.

Therefore, the present applicant has provided a predetermined light-shielding period, and has adopted an all-pixel reading method in which data of all pixels obtained by the immediately preceding exposure is read out using the light-shielding period. However, in the driving of the light-blocking shutter for setting the light-blocking period, a mechanical (gear or the like) response delay occurs. That is, since a complete light-shielding state is required in the light-shielding period for data reading, the light-shielding shutter is operated slightly before the light-shielding period in consideration of the response time,
In this case, the amount of light at the time of the immediately preceding exposure decreases in the response operation (operation until complete light shielding). In addition, when the amount of light emitted from the light source is adjusted by the aperture mechanism, the response time of the light-blocking shutter changes depending on the opening state of the aperture.
There is a problem that the insufficient light quantity changes.

FIG. 7 shows the relationship between the aperture member of the aperture mechanism and a light-shielding shutter for setting a light-shielding period. For example, an aperture blade 3 and a light-blocking shutter 4 are arranged so as to block a light beam (or aperture opening) 100 from a light source, and one of the aperture blades 3 rotates about a rotation axis 3A and the other light-blocking shutter 4 rotates. It is mounted so as to rotate and rotate clockwise about the shaft 4A. The aperture blade 3 is driven so that the luminance signal of the video signal is constant. For example, by increasing the light amount at a far point and decreasing the light amount at a near point, a good image can be obtained. I have. Further, the light-blocking shutter 4 is driven at a predetermined rotation speed by one.
By rotating, the light beam 100 is moved so as to completely block the light beam 100 for a period of 1/60 second.

However, in such a configuration, the aperture blade 3
And the light-blocking shutter 4 rotate in the same direction, so that the light-blocking shutter 4
The timing of blocking 00P is different, and the response time for completely blocking the light flux 100P changes.
That is, in FIG. 7, in order to completely block the actual light beam 100P, when the aperture blade 3 is fully opened, the rotation angle θ
1, when the aperture blade 3 is at the position indicated by the solid line, the rotation angle θ2;
When located at the position indicated by the two-dot chain line, the light-shielding shutter 4 moves by the rotation angle θ3, and as a result, the response time changes.

FIG. 8 shows the relationship between the light amount (C) of the light beam 100 and the response time (light amount is plotted on the vertical axis and time is plotted on the horizontal axis). In this figure, the aperture blade 3 is fully opened. , Luminous flux 10
0 when the response time ta1 is 2 mS (se
This is a comparison between the case of c) and the case where the response time ta2 when the diaphragm blade 3 is at the position where the half of the aperture opening 2 is closed and the light beam 100 of the other half is shielded is 1 ms.

When the throttle is fully opened, the response time ta1 is 2 ms.
Is satisfied, the light amount C per unit time when the diaphragm is fully opened is 4
V, if the exposure time (tb) is 1/60 second, usually CCD
The amount of charge stored at 1 is tb × C = 1/60 [ms] × 4 [V] ≒ 66.67 [mVS]. On the other hand, the charge amount in the case of providing the light-blocking period is as follows: tb × C− (１ ／) ta1 × C = 1/60 [ms] × 4 [V], where the attenuation line at the response time ta1 is regarded as a straight line. − (１ ／) · 2 [mS] × 4 [V] ≒ 62.67 [mVS], so that the light amount when the light-shielding period is provided is 94% (6% light amount decrease) of the normal light amount. , Image brightness is 6%
descend.

On the other hand, when the throttle is half open, the response time ta2 is 1 ms.
If the light amount C at this time is 2 V and the exposure time (tb) is 1/60 second, the amount of charge accumulated in the CCD 1 is usually tb × C = 1/60 [mS] × 2 [V] ≒ 33.33 [mVS], and the charge amount in the case of providing the light shielding period is tb × C− (１ ／) ta2 × C = 1/60 [ms] × 2 [V] − (1/2) 2) · 1 [mS] × 2 [V] ≒ 32.33 [mVS], so that the light amount when the light shielding period is provided is 97% (3% decrease in light amount) of the normal light amount, and the image brightness is also high. Decrease by 3%.

As described above, when the response times ta1 and ta2 are different, the rate of decrease in the amount of photographing light is different, and the decrease in the light amount increases as the response time ta increases, and as a result, the brightness of the image changes. I do.

The response time ta of the light-shielding shutter
Insufficient light amount also occurs when the shutter time is variably controlled by the electronic shutter function. That is, if the case where the above-described aperture mechanism is not provided and the amount of exposure to the CCD 1 is controlled only by the electronic shutter function is considered, the above-mentioned response time ta is constant, but the time for accumulating electric charges (shutter speed) is short. Change. Therefore, also in this case, the ratio of the insufficient light amount to the entire exposure amount changes, and the inconvenience that the brightness of the image changes similarly to the above occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an electronic endoscope that provides a light-shielding period and reads out all pixels. It is an object of the present invention to provide an electronic endoscope apparatus that sets a light-shielding period in which the brightness of an image can be stabilized without variation in deterioration.

[0016]

According to an aspect of the present invention, there is provided an electronic endoscope apparatus for setting a light-shielding period according to the first aspect of the present invention. An aperture mechanism or an electronic shutter circuit), a liquid crystal shutter for shutting off light to the image sensor, and a light-shielding period for turning on and off the liquid crystal shutter and reading out signals of all pixels stored in the image sensor. A liquid crystal shutter control circuit for setting. According to a second aspect of the present invention, there is provided an image sensor output pixel mixture readout method for mixing and outputting image signals accumulated in the image sensor between upper and lower lines to form a moving image, and the image sensor in one exposure. In which the signals of all the pixels stored in the pixel are read out using the light-shielding period to form a still image.

According to the above arrangement, the liquid crystal shutter is disposed, for example, at a light emitting portion of a light source device, and is normally turned on by a liquid crystal shutter control circuit to be in a transmitting state. Irradiated into the observation body. On the other hand, when a light-shielding period is provided, the liquid crystal shutter is turned off, so that the light source light is blocked by the liquid crystal shutter, thereby setting a complete light-shielding period. The off operation of the liquid crystal shutter is not a mechanical operation and is completed in a very short time, and the shortage of light amount and the variation caused by the response time are negligible. Also,
This liquid crystal shutter may be disposed on the scope side, for example, on the output section of the light guide at the tip or on the light incident side of the solid-state imaging device.

According to the configuration of the second aspect, a high-quality still image is formed by the all-pixel reading method using the light-shielding period. In this all-pixel reading process, for example, a predetermined (1
The charge accumulated by exposure during the 1/60 second period (vertical synchronization period) of the second period (1/60 second)
(Seconds), the odd lines of the image sensor are read, and the remaining even lines are read in the third (at the next exposure) period, and these data are stored in a predetermined memory. Then, the second period is set as a light shielding period so that the even lines can be read.

That is, if the charges of the next exposure are accumulated in the second period during which the accumulated charges of the odd lines are read out, the remaining even lines cannot be read. Therefore, the second period is a light-shielding period, and the accumulated charges of the even-numbered lines are read in the third period. This gives 1
The signals for all the pixels of the image sensor obtained by the second exposure can be read.

Next, the odd-line video signal and the even-line video signal stored in the memory are subjected to a pixel mixing process by a mixing circuit. That is, this pixel mixing process forms a signal equivalent to the conventional pixel mixing readout method at the time of output of the image sensor, which is performed at the time of signal output from the image sensor, but is based on data obtained by one exposure. This is distinguished from the above-described conventional reading method in that pixel mixing is performed.

On the other hand, at the time of normal moving image display, the pixel mixture readout method at the time of output of the image sensor is selected, and pixels of two horizontal lines are mixed and read when output from the image sensor as in the conventional case. Therefore, in the case of a moving image, it is possible to obtain an image that faithfully reproduces the movement of the subject or the like by imaging over time.

[0022]

1 and 2 show a configuration of an electronic endoscope apparatus to which a light source device according to an embodiment is applied. In FIG. 1, a scope (electronic endoscope) 10 includes:
A CCD 12 provided with a color filter similar to that described with reference to FIG.
A light guide 15 for guiding the light to the tip is provided. 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 is connected to the CCD 12, and a timing generator 19 and a microcomputer (microcomputer) 20 for performing various controls are connected to the drive circuit 18. An operation signal of the freeze switch 16 is input to 20. The CCD drive circuit 18 includes a microcomputer 20
Based on the above control, a timing signal is input, and drive control of a pixel mixed readout method at the time of CCD output for a moving image and an all pixel readout method for a still image is performed.

For example, in the case of this all-pixel reading method,
Two types of pulses are supplied from the CCD driving circuit 18 for reading out the accumulated data for all the pixels accumulated in the CCD 12 in one exposure by dividing the data into odd lines and even lines and also shifting in time. Based on this, control is performed to sequentially and sequentially read out the odd-line signal and the even-line signal from the CCD 12. Incidentally, in the pixel mixed readout method at the time of CCD output, one kind of readout pulse is applied to each line.

On the other hand, in the light source section for supplying light to the light guide 15, the light source lamp 14 and the light guide 15
An aperture blade 22 and a liquid crystal shutter 23 having a liquid crystal portion disposed in a light passage area are disposed between the aperture driving circuit 22 and the aperture driving circuit 22. The liquid crystal control circuit 26 is connected.
The lighting of the lamp 14 is controlled by a lamp driving circuit 27.

The aperture driving circuit 25 is provided with a DVP (to be described later).
The diaphragm blade 22 is driven based on the luminance signal obtained in (35), and the amount of light emitted from the lamp 14 is adjusted. Also,
The liquid crystal control circuit 26 turns off the liquid crystal shutter 23 at a predetermined timing after the freeze switch 16 is pressed, and completely shuts off light for a predetermined light-shielding period of 1/60 second. That is, when the liquid crystal shutter 23 is turned on, it shows light transmissivity, and when turned off, it shows light impermeability.
The light is instantaneously shut off by being guided to the entrance end of No. 5 and turned off when a still image is formed.

In FIG. 1, a first memory 30 for storing the image data of the odd-numbered lines for reading out all the pixels via an A / D converter 29 is provided at a subsequent stage of the CCD 12.
A second memory 31 for storing image data of the even-numbered lines, a third memory 32 for storing the data of the first memory 30 as it is, and delaying the readout timing by 1/60 second; A circuit 33 is provided.

That is, all pixel signals obtained by the CCD 12 are temporarily stored in the respective memories 30 and 31 in a state of being divided into odd-numbered line data and even-numbered line data. By delaying the line data by 1/60 second, the line data has the same phase as the even line data stored in the second memory 31. As a result, both image data can be read at the same time, and the next-stage mixing circuit 33 adds and mixes the pixel data of the odd-numbered line of the third memory 32 and the pixel data of the even-numbered line of the second memory 31 (still image). Pixel mixing process). Therefore,
In the case of a still image, the mixing circuit 33 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 processed by the memories 30 to 32 and the mixing circuit 33 described above. As shown on the left side of the figure, the first memory 3
0 and the third memory 32 store the data of the odd lines (1, 3, 5,... Lines) of the CCD 12, and as shown on the right side of the figure, the second memory 31 stores the even lines (2, 3). , 4, 6,... Lines).

The two data in the memories 32 and 31 are pixel-mixed in order from the upper side as indicated by a solid line or a dotted line by a mixing circuit 33, for example. ... The addition operation data of 4 lines + 5 lines... Is output as odd field data, and the addition operation data of 1 line + 2 lines, 3 lines + 4 lines, 5 lines + 6 lines. Output as field data.

In FIG. 1, an image switching circuit 34 for switching between a moving image and a still image is provided at a stage subsequent to the mixing circuit 33. In the image switching circuit 34, the A / D is connected to a terminal a for forming a moving image. The output of the converter 29 is supplied via the L line, the output of the mixing circuit 33 is given to the other terminal b, and when the freeze switch 16 is pressed, the terminal a is switched to the terminal b. A DVP (Digital Video Processor) 35 is connected to the image switching circuit 34. In the DVP 35, various processes including gamma correction are performed, for example, a color difference signal and a luminance signal are formed. A memory, a D / A converter, and the like for storing data of the odd field and the even field are provided at a subsequent stage of the DVP 35.
Output to the monitor via the / A converter.

The embodiment has the above configuration, and its operation will be described with reference to FIGS. FIG. 3 (A)
, The fields O (Odd) / E (Ev
As the signal en), a timing signal for forming a one-field image in 1/60 second is used as in the related art. In the normal state, the liquid crystal shutter 2 is set to execute the moving image processing, that is, the pixel mixture readout method at the time of CCD output.
3 is turned on by the liquid crystal control circuit 26, and the light beam from the light source lamp 14 is radiated through the light guide 15 from the distal end to the body to be observed.

By this light irradiation, electric charges corresponding to the image light from the body to be observed are accumulated in the CCD 12 at the distal end.
The accumulated charges are read out by adding the pixels between the upper and lower lines by a driving pulse from the CCD driving circuit 18, and the pixel mixture signal described with reference to FIG. 6 is output. The moving image signal is supplied from the A / D converter 29 to the image switching circuit 34 via the through line L, and is supplied to the DVP 35 via the terminal a of the image switching circuit 34. The operation after the DVP 35 is the same as the conventional operation, and a moving image is displayed on the monitor based on the odd and even field signals.

The luminance signal obtained by the DVP 35 is supplied to the microcomputer 20, and the aperture blade 22 is driven by the control of the microcomputer 20 and the aperture driving circuit 25, whereby the luminance of the image is maintained constant. You.

On the other hand, when the freeze switch 16 of the scope 10 shown in FIG. 1 is pressed, the microcomputer 20 switches the image switching circuit 34 to the terminal b, and switches to the all-pixel reading method. At the same time, for example, as shown in FIG.
The liquid crystal shutter 23 is turned off for 1/60 second, during which time the output light from the light source unit is shut off as shown in FIG. Therefore, the image data from which all the pixels are read out has the light output L of the 1/60 second period immediately before the light shielding period.
Due to t, the charge is accumulated in the CCD 12.

That is, FIG. 3D shows the read pulse P1 of the odd line on the left side of FIG. 2, and FIG. 3E shows the read pulse P2 of the even line on the right side of FIG. Odd line data and even line data are sequentially read from the CCD 12 by the read pulse P1 without the pulse and the read pulse P2 without the pulse at t1. Therefore, the reading of the odd-numbered lines is performed during the light-shielding period (t1 to t2), and the reading of the even-numbered lines is performed during the next period (t2 to t3).

FIG. 3G shows the operation of the electronic shutter. In this case, the accumulated charges in the rising period of the pulse are swept out, and the accumulated charges in the non-rising period are read. Therefore, the above still image data (accumulated charge)
Is obtained by the exposure g1 of the shutter time tb after the electric charge is swept out.
It is read by the drive circuit 18. The above exposure g
In the light-shielding period after one (t1 to t2), the sweeping is omitted.

By the way, in the above-described light-shielding period, it is necessary to set a complete light-shielding state so that unnecessary charges are not accumulated in the CCD 12, and for that purpose, control is performed in consideration of a response time. FIG. 4 shows an operation corresponding to FIG. 3 assuming that the light shielding shutter of FIG. 7 is used. In the case of the light shielding shutter, as shown in FIG. In consideration of a mechanical response delay time (response time) ta of a drive unit (gear or the like) of the shutter (4), a pulse that is inverted earlier by the time ta is formed.

When the light-shielding shutter is driven, the light emitted from the light source section attenuates in a quadratic curve with the response time ta as shown in FIG. 4C or FIG.
Thereafter, the state shifts to a complete light shielding state. Therefore, in the light output Lt for a still image, the light amount becomes insufficient by the loss of the light amount La, and the light amount La changes with the response time.

However, the liquid crystal shutter 23 used in this example
Performs an electrical operation, so that it is possible to shift to a complete light shielding period with an extremely short response time. As a result, the variation in the decrease in the amount of light that has occurred when the light-shielding period is set is also eliminated, and a still image signal with good brightness (luminance) is obtained regardless of whether the object to be observed is at the far point or near point. It becomes possible.

Then, the CCD 1 is controlled by such light amount control.
2, the odd line data is written to the first memory 30 in FIG. 1, and the other even line data is written to the second memory 31 in FIG.
The odd line data in the memory 30 is 1/60 in the third memory 32.
With a second delay, the phase of the even-numbered line data in the second memory 31 matches the phase.

Next, the respective data stored in the memories 32 and 31 are pixel-mixed by the mixing circuit 33, and from the mixing circuit 33, as shown in FIG.
.. Are output as odd-numbered (Odd) field data, and the added data of 1 line + 2 lines, 3 lines + 4 lines... Are output as even-numbered (Even) field data.
A still image is displayed on the monitor based on these field data. Since the still image is formed by all pixel data obtained at the same exposure, high image quality is obtained. Therefore, even if the endoscope itself shakes or the subject moves during 1/60 second, it is possible to observe a clear still image with a small influence.

In the above embodiment, even when the electronic shutter function is employed, stable image brightness can be obtained. That is, as can be understood from FIG. 4D, when the electronic shutter is variably controlled, the exposure g1 shown in FIG.
Is changed, and also in this case, the influence of the light quantity shortage La varies. However, in this example, since the response time ta has a negligible value, even if the shutter time Tb changes, the effect of the light quantity shortage La can be ignored.

In the above example, the CCD 12
In contrast, while adopting the mixed readout method at the time of output, the movement of the subject etc. was faithfully reproduced, but in the case of this moving image, if a clear image without blurring is to be pursued, the shading period is also required for the moving image formation processing. Can be adopted for the all-pixel readout method using.

FIG. 5 shows another example of the embodiment, in which a liquid crystal shutter for setting a light shielding period is arranged on the scope side. That is, the liquid crystal shutter 41 is provided on the output side of the light guide 15 of the scope 40 (e.g., before the irradiation window), or the liquid crystal shutter 43 is arranged between the rear side (or inside) of the objective optical system 42 and the CCD 12. ,
These liquid crystal shutters 41 and 43 can be controlled by the microcomputer 20. The liquid crystal shutter 41 having such an arrangement
Also, the light-shielding period can be set, and the same effect as described above can be obtained.

[0046]

As described above, according to the present invention,
A liquid crystal shutter is arranged on the light source unit or the scope side, and a predetermined light shielding period is set by controlling the liquid crystal shutter on / off. Therefore, even when the aperture opening amount or the electronic shutter speed is different, the light shielding period can be set. , The response time becomes extremely short, and the variation in light quantity decrease can be ignored. Therefore, even in the method of reading out all pixels using the light-shielding period, an image with stable brightness can be obtained regardless of the imaging distance and the like.

According to the second aspect of the present invention, there is an advantage that a high-quality still image with stable brightness can be obtained, and a smooth image in which the motion is faithfully reproduced can be formed for a moving image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an electronic endoscope apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing image data processed by a memory and a mixing circuit of FIG. 1;

FIG. 3 is a waveform chart showing an operation of signal reading when forming a still image in the embodiment.

FIG. 4 is a waveform diagram illustrating a relationship between a response time and an insufficient light amount when a light-shielding shutter is used.

FIG. 5 is a configuration diagram of a scope showing another example of a liquid crystal shutter arrangement in the embodiment.

FIG. 6 is a diagram illustrating a configuration of a color filter in a conventional CCD and pixel mixture readout.

FIG. 7 is a diagram illustrating a configuration of an aperture blade and a light shielding shutter in a conventional light source device.

8 is a diagram showing a relationship between a response time of a light-shielding shutter and an insufficient light amount in the apparatus of FIG. 7;

[Explanation of symbols]

 12, 1 CCD, 14 light source lamp, 16 freeze switch, 20 microcomputer (control means), 22, 3 diaphragm blade, 23, 41, 43 liquid crystal shutter, 25 diaphragm drive circuit, 26 liquid crystal shutter Control circuit, 30, 31, 32 ... memory, 33 ... mixing circuit.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/225 H04N 5/225 C 7/18 7/18 M 9/07 9/07 A

Claims (2)

[Claims] 1. An exposure amount control means for controlling an exposure amount in an image pickup device, a liquid crystal shutter for blocking light to the image pickup device, and an on / off control of the liquid crystal shutter, so that all of the liquid crystal stored in the image pickup device are stored. An electronic endoscope apparatus for setting a light-shielding period, comprising: a liquid crystal shutter control circuit for setting a light-shielding period for reading out pixel signals. 2. An image pickup and output pixel mixture readout method for mixing and outputting image signals accumulated in the image pickup device between upper and lower lines to form a moving image, and a method of accumulating the image signal in the image pickup device by one exposure. 2. The electronic endoscope apparatus according to claim 1, wherein a signal of all pixels is read out using the light-shielding period and an all-pixel reading method for forming a still image is adopted.