JPH0797181B2 - Electronic endoscope - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic endoscope that sequentially colors illumination light into three colors to perform color imaging in a frame sequential method.

[Conventional technology]

In recent years, a solid-state imaging device such as a charge-coupled device (CCD) is built in the tip of an endoscope, and illumination light is sequentially colored in red (R), green (G), and blue (B), and the subject is frame-sequential. An electronic endoscope has been developed for color imaging. An external light source is connected to the endoscope body, and illumination light from this is incident on the light guide through the rotary filter to illuminate the subject. The rotary filter is formed by arranging R, G, and B color filter components along the circumference of the rotary disk. Then, when the image of each color component is sequentially written in each frame memory, and the images of the three color components are written in the frame memory, the images of the three frame memories are simultaneously read out and one full color image is displayed on the CRT monitor. It is displayed as an image.

[Problems to be solved by the invention]

As described above, in the frame-sequential method, three color component images captured during one rotation of the rotary filter are combined to obtain one full-color image. Then, a color shift occurs between the three color component images, and the image quality deteriorates.

In order to deal with this, it is conceivable to increase the rotation speed of the rotary filter, but this makes the imaging period of each color component image short, and the illumination light of sufficient light quantity is not emitted to the subject, which is not preferable.

This invention has been made to deal with the above-mentioned circumstances,
An object of the present invention is to provide a frame sequential electronic endoscope capable of obtaining a still image with less color shift without increasing the rotation speed of the rotary filter and reducing the amount of illumination light.

[Means for solving problems]

The electronic endoscope according to the present invention includes a lamp 42 for generating illumination light for observation, a strobe 58 for generating a flash light, and a lamp 42 and a strobe 58 in synchronization with the rotation of the rotary filter 44 when the release switch 21 is pressed. A timing generator 38 for switching light emission is provided.

[Action]

According to the electronic endoscope of the present invention, the emission of the first flash light is finished at the end of the coloring period of the first color of the rotary filter 44, and the second flash light emission is performed in the coloring period of the second color. The third flash light emission starts at the start of the third color coloring period, and each color component image is captured only during the period during which the flash light is emitted. Therefore, the third color from the start of capturing the first color component image The time until the end of capturing the component image is shortened compared to the conventional case, and a still image with less color shift can be recorded without increasing the rotation speed of the rotary filter and reducing the illumination light amount.

〔Example〕

An embodiment of an electronic endoscope according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of one embodiment.
This embodiment includes an endoscope body 10 and a light source unit 12. The light source unit 12 has a function as a general light source,
It also has a function as a video processor. Here, the endoscope body 10 is not limited to a medical one for observing the inside of a body cavity,
It may be an industrial one for observing the inside of a thin tubular member inside the machine.

A solid-state image pickup device (here, CCD) 16 for picking up an image of a subject through an objective lens 14 is provided at the tip of the endoscope body 10.
The CCD 16 has a narrow tip, so the CCD16 has a charge storage unit (imaging unit).
And a transfer unit for reading, and does not have a light shielding unit that functions as a shutter. The shutter function is provided on the light source unit 12 side, as described later. The light source unit 12 outputs the output signal of the CCD 16 as a two-phase signal through the preamplifier 18.
To a common mode rejection (CMR) amplifier 22 therein.

The endoscope body 10 further has a light guide 20 formed of an optical fiber bundle. One end of the light guide 20 is the light source unit 12
And the other end is guided to the tip of the endoscope. Illumination light from the light source unit 12 is applied to the subject through the light guide 20.

The output of the CMR amplifier 22 is the sample / hold (S / H) circuit 2
4. The data is written in any of the frame memories 30a, 30b, 30c via the analog / digital (A / D) converter 26 and the multiplexer 28. The multiplexer 28 outputs image signals of R, G, and B color components to the frame memories 30a, 30b, and 30c, respectively.
To be written to.

The outputs of the frame memories 30a, 30b, 30c are R / G / B signal output terminals 35a via digital / analog (D / A) converters 32a, 32b, 32c and low pass filters (LPF) 34a, 34b, 34c, respectively. Output from 35b and 35c. These R,
A CRT color monitor, a magnetic disk device and the like are connected to the G and B signal output terminals 35a, 35b and 35c.

A driver 36 for generating clock pulses for driving the CCD 16 is also provided in the light source unit 12.

Each circuit in the light source unit 12 is a timing generator 3
Timing is controlled by 8 and 40. The writing speed and the reading speed for the frame memories 30a, 30b, 30c are different. Writing to the frame memories 30a, 30b, 30c is C
It is controlled by the timing generator 38 so as to be synchronized with the imaging speed of the CD 16. Frame memory 30a, 30b, 30c
Read from R, G, B signal output terminals 35a, 35b, 35c
Is controlled by the timing generator 40 so as to synchronize with a data transfer rate required for a device such as a CRT color monitor and a magnetic disk device connected to the. S / H circuit 24, A
/ D converter 26, multiplexer 28, frame memory 30a, 3
A timing generator 38 is connected to 0b, 30c and the driver 36. Frame memory 30a, 30b, 30c, D / A converter 32
The timing generator 40 is connected to a, 32b, and 32c. In addition, the release switch provided on the endoscope body 10
The signal from 21 is supplied to the timing generator 38.

The light source unit 12 includes, as a light source, a lamp (for example, a xenon lamp) 42 that emits continuous light for observation, and a strobe 58 that emits flash light for still image recording. A lamp power supply circuit 54 is connected to the lamp 42. A strobe control circuit 56 is connected to the strobe 58.

When the mirror 60 is at the position shown by the solid line in the drawing, the illumination light from the lamp 42 is incident on the light guide 20 via the relay lens and the rotary filter 44. When the mirror 60 is at the position shown by the broken line in the drawing, the illumination light from the strobe light 58 is reflected by the mirror 60 and then enters the light guide 20 via the relay lens and the rotary filter 44. The displacement of the mirror 60 is controlled by the strobe control circuit 56. When the lamp 42 emits light, the mirror 60 is in the position shown by the solid line in the figure, and when the strobe 58 emits light, the mirror 60 is in the position shown by the broken line in the figure. Lamp power circuit
54, the strobe control circuit 56 is selectively controlled by the timing generator 38.

The rotary filter 44 has the above-mentioned shutter function and the function of sequentially coloring the illumination light into R, G, and B colors. Rotating filter
As shown in FIG. 2, reference numeral 44 is a disk in which R, G, and B color filter components 70, 72, and 74 are arranged at predetermined intervals on the circumference. The disk portion between the color filter components 70, 72, 74 functions as a shutter for blocking the illumination light to the light guide 20 for reading the signal from the CCD 16. Through holes 76, 78, 80 for generating read pulses are provided outside the rearmost portion of each color filter component 70, 72, 74 in the rotational direction, and a start pulse is provided outside the rearmost portion of the B filter 74 in the rotational direction. A through hole 82 for generation is also provided.

The rotary filter 44 is driven by a step motor 46 that is PLL controlled by a speed control circuit 48. A photocoupler 50 that includes a light emitting element and a light receiving element sandwiching the rotary filter 44 at the edge of the rotary filter 44, and generates a read pulse and a start pulse by detecting the through holes 76, 78, 80, 82.
Is provided. The start pulse and the read pulse output from the photocoupler 50 are supplied to the timing generator 38 and the speed control circuit 48 via the amplifier 52.

Next, the operation of this embodiment will be described with reference to FIGS. The speed control circuit 48 is provided with a reference signal generator that generates a synchronization pulse (for example, a pulse at 130-second intervals) that serves as a reference for the rotation control of the rotary filter 44. Rotate at a speed synchronized with. With the rotation of the rotary filter 44,
In the optical path of the illumination light incident on the light guide 22, R,
G and B color filters 70, 72 and 74 are inserted. As a result, as shown in FIG. 3B, the illumination light is sequentially colored R, G, and B with a light-shielding period (low-level period in FIG. 3) interposed therebetween.

Although not shown in FIG. 3, a read pulse is generated at the end of each of the R, G, and B illuminations, and a start pulse is generated at the end of the B illuminations. The speed control circuit 48 controls the rotation speed of the step motor 46 so that the start pulse and the synchronization pulse are synchronized.

The timing generator 38 uses the lamp power supply circuit 54 during normal shooting (when the release switch 21 is not turned on).
A control signal for causing the lamp 42 to emit light is supplied to the strobe control circuit 56, and a control signal for causing the strobe 58 to not emit light and the mirror 60 being in the position shown by the solid line in the drawing is supplied to the strobe control circuit 56. FIG. 3C shows the position of the mirror 60, which is at the position indicated by the broken line in the figure at the high level and at the position indicated by the solid line in the figure at the low level. Therefore, at this time, the illumination light for observation from the lamp 42 is sequentially colored into R, G, and B through the rotary filter 44 and is incident on the light guide 20.

During the period when the illumination light is colored R, G, B, the CCD 16 accumulates charges corresponding to each color component image information, and R, G, B
This charge is read during the light-shielding period immediately after the G and B coloring periods. That is, the accumulated charge is read from the CCD 16 in response to the read pulse generated at the end of each of the R, G, B illumination periods, and stored in the frame memories 30a, 30b, 30c.
In this way, the image of the subject captured by the frame sequential method is output from the R, G, B signal output terminals 35a, 35b, 35c, and the image of the subject is displayed on the CRT color monitor in real time.

Since the display on this CRT color monitor is a moving image display,
When it is desired to observe the subject in more detail, a still image is displayed instead of the moving image. Here, if the writing to the frame memories 30a, 30b, 30c is simply interrupted and the image finally written in the frame memories 30a, 30b, 30c is repeatedly read out, the color misregistration occurs as in the conventional case. In this embodiment, the following special still image recording is performed.

While looking at the screen, the operator closes (turns on) the release switch 21 at the timing when he / she wants to record a still image (Fig. 3 (a)). The timing generator 38 changes from the moving image recording mode to the still image recording mode accordingly. The timing generator 38 is a mirror as shown in FIG.
60 is displaced to the position shown by the broken line in the figure, and the lamp current is reduced to a minute level other than 0 (dashed line) through the lamp power supply circuit 54 as shown in FIG. 3 (e).
It should be noted that the incidence of illumination light from the lamp 42 on the light guide 20 is blocked by the mirror 60, so that it is necessary to reduce the lamp current.

Further, the timing generator 38 causes the strobe 58 to emit light three times in synchronization with the read pulse, as shown in FIG. 3 (d). The strobe control circuit 56 finishes emitting the first flash light at the end of the R illumination period, and outputs 2 flashes in the middle of the G illumination period.
The third flash is emitted and 3 at the start of the B illumination period.
The strobe 58 is made to emit light so that the second flash emission starts. Here, since the amount of illumination light is 0 except during the period when the flash light is emitted, each color component image is captured only during the flash light emission period. Therefore, the time from the start of capturing the R component image to the end of capturing the B component image is shortened as compared with the conventional case, and the rotation speed of the rotary filter 44 is increased and the illumination light amount is not reduced. , It is possible to record a still image with little color shift.

Thereafter, when the illumination period of B ends, the timing generator 38 returns from the still image recording mode to the moving image recording mode. That is, as shown in FIG. 3 (c), the mirror 60 returns to the position shown by the solid line in the figure, and the lamp current is returned to the high level as shown in FIG. 3 (e). Here, the image recorded as a still image is stored in the magnetic disk device connected to the R, G, B signal output terminals 35a, 35b, 35c.

It should be noted that the present invention is not limited to the above-described embodiments, but can be variously modified. For example, in the above description, the rotary filter
Although the size (circumferential length) of each of the 44 color filter components 70, 72, and 74 has been described as constant, the sensitivity of the CCD differs depending on the color, and accordingly the color filter components
The sizes of 70, 72 and 74 may be different. Here, in general, the sensitivity of CCD is deteriorated in the order of R, G, and B, so that the sizes of the color filter components are increased in the order of R, G, and B. Therefore, in this case, the smallest R component may be arranged at the position of the G component in the above-mentioned embodiment. Further, it is not necessary to provide both the lamp 42 and the strobe 58 as the light source, and only the strobe 58 may be used. In this case, if the size of each color filter component is different, the number of times the strobe emits light is controlled or the light emission time is controlled according to the size.

〔The invention's effect〕

As described above, according to the present invention, when a still image recording instruction is input, flash light is generated instead of the observation illumination light in synchronization with the coloring operation of each color, and 1 flashes at the end of the coloring period of the first color. The second flash emission is completed, the second flash emission is performed in the second color coloring period, the third flash emission is started at the start of the third color coloring period, and this flash is emitted. Since each color component image is captured only during the period, the time from the start of capturing the first color component image to the end of capturing the third color component image is shortened as compared with the conventional one, and the rotation speed of the rotary filter is increased. Without reducing the amount of illumination light
There is provided an electronic endoscope capable of recording a still image with little color shift.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an electronic endoscope according to the present invention, FIG. 2 is a plan view of a rotary filter used in this embodiment, and FIGS. 3 (a) to (e) are drawings of this embodiment. It is a signal waveform diagram explaining an operation. 10 …… Endoscope body 12 …… Light source unit 16 …… Solid-state image sensor (CCD) 20 …… Light guide 21 …… Release switch 30a, 30b, 30c …… Frame memory 42 …… Lamp 44 …… Rotary filter 58 ...... Strobe 60 …… Mirror

Claims (1)

[Claims] 1. A field-sequential electronic endoscope that sequentially colors illumination light into three colors. First illumination means that is constantly generated during observation of the illumination light for normal observation and during still image recording, and a still image. Second illumination means for generating a flash light to obtain the light, switching means for switching the illumination light from the first illumination means and the illumination light from the second illumination means with which a subject is irradiated, and a still image When a recording instruction is input, the illumination light emitted to the subject by the switching means is switched from the illumination light from the first illumination means to the illumination light from the second illumination means, and the second illumination light is emitted. The illumination means ends the first flash emission at the end of the coloring period of the first color,
The second flash emission is performed within the second color coloring period, and the third flash emission is started at the start of the third color coloring period.
At the end of the third color coloring period, the illumination light is returned to the first color again.
And an illumination light control means for switching to illumination light from the illumination means.