JPH0617394Y2 - Endoscope using image sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an endoscope using an image sensor for performing field sequential illumination using a complementary color filter.

[Technical Background of the Invention and Problems Thereof] In recent years, various endoscopes using a solid-state imaging device such as a charge-coupled device as an imaging means have been proposed.

An endoscope using the above solid-state imaging device can prevent deterioration of image quality due to breakage of fibers in an endoscope using an image guide formed of an optical fiber bundle (fiber bundle), and record an image. Since it has advantages such as ease of processing, etc., and further miniaturization and improvement in resolution are expected with the progress of integration technology, it is widely used in the future.

By the way, when performing color imaging using the above-mentioned solid-state imaging device, under white illumination, a mosaic filter provided in front of the light-receiving part of the solid-state imaging device directly decomposes into signals corresponding to pixels of three primary colors. Illumination and light reception (imaging) are sequentially performed with light of each of the three primary color wavelengths, and those captured with the light of each of these wavelengths are written into each frame memory and simultaneously read to form R, G, and B color signals. , A color TV monitor displays a color image by applying to RGB input terminals.

An endoscope of the field-sequential illumination system that sequentially illuminates with the light of each wavelength as described in Japanese Patent Application Laid-Open No. 51-59662 discloses a white illumination lamp that emits white light as shown in FIG. ，
By rotating the rotary filter 2 formed by the fan-shaped transmission filters 1R, 1G, and 1B that pass the respective wavelength regions of the three primary colors of green and blue, the transmission filters 1R and 1R are rotated.
G and 1B are sequentially transmitted, and as shown in FIG. 2, red,
Each frame is sequentially illuminated with green and blue lights. In this conventional example, the photoelectric conversion output is poor and S /
There is a drawback that N is low, and since the rotating filter is used, the light source device cannot be downsized.

[Object of the Invention] The present invention has been conceived in view of the above-mentioned points. The photoelectric conversion output is increased to improve the S / N, and it is possible to prevent the deterioration of the resolution even in a subject image with large movement, and the light source device. An object of the present invention is to provide an endoscope using an image pickup device that can be downsized.

[Summary of the Invention] The present invention is an endoscope in which an object is sequentially illuminated with illumination light of different wavelength ranges and an image is picked up by an image pickup means, and a filter main body formed of stripe-shaped three-color filters, and this filter. A light-shielding plate which is disposed adjacent to the main body and has slit-shaped transmission windows each having a stripe width of the filter main body formed with three times the stripe width as one cycle, and a right angle with respect to a slit in each window of the light-shielding plate. It comprises a movable means for moving the light shielding plate in a stepwise direction in a direction, and a cylindrical lens formed in a shape connected to the light shielding plate in the vertical direction and provided adjacent to the light shielding plate.

[Embodiment of the Invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

3 to 6 relate to the first embodiment of the present invention,
The drawing shows the entire structure of the first embodiment, FIG. 4 shows the rotationally driven filter used in FIG. 1, FIG. 5 shows the transmission characteristics of the filter, and FIG. It shows the amount of light transmitted to the.

As shown in FIG. 3, the endoscope 11 of the first embodiment has an objective lens 14 for image formation on a rigid tip (configuration) portion 13 formed on the tip side of a flexible and elongated insertion portion 12. The solid-state image sensor 15 is arranged so that the light receiving portion (light receiving surface) faces the image forming position of the objective lens 14. Adjacent to the image pickup means composed of the objective lens 14 and the solid-state image pickup element 15,
The emission end of the light guide 16 inserted through the insertion portion 12 is fixed to the tip portion 13, and the illumination light incident on the light-incident end of the light guide 16 on the near side is transmitted to the light distribution lens 17 from the emission end. The subject can be illuminated via the.

Light source device 1 to which the incident end of the light guide 16 is attached
Reference numeral 8 reflects the illumination light of the illumination lamp 19 by the concave reflecting mirror 20, further condenses it by the condenser lens 21, and irradiates the incident end of the light guide 16. Therefore, the filter 2 rotationally driven by the motor 22 is provided between the condenser lens 21 and the incident end of the light guide 16.
3 is provided, and the illumination light with which the incident end of the light guide 16 is irradiated is configured to be light in each wavelength range transmitted through the filter 23.

That is, the filter 23 is, as shown in FIG. 4, a cyan complementary color filter 23 that transmits light in the wavelength bands of green and blue, for example.
It is composed of a white complementary color filter 23W that transmits light in the C, red, green, and blue wavelength ranges, and a yellow complementary color filter 23Y that transmits light in the red and green wavelength ranges. In the present invention, a filter having a filter characteristic that allows light of two or more colors (wavelength regions) to pass is referred to as a complementary color filter, whereas a filter that allows light of each single color (wavelength region) of the three primary colors to pass. Call.

These complementary color filters 23C, 23W and 23Y are green, blue; red, green, blue; red and green 2 to 3 as shown in FIG.
Since it exhibits a transmission characteristic of transmitting in the wavelength range of, the object is frame-sequentially irradiated with the light of each wavelength in the wavelength range as shown in FIG. It is supposed to be illuminated.

Thus, the motor 22 is controlled by the motor control unit 24 so as to rotate at a constant speed. Further, the illumination light is shielded for a short period of time by the light shielding portion at the boundary between the complementary color filters 23C, 23W, 23Y, and during this period, it is detected by a photodetector such as a photodiode (not shown), and a synchronization signal is generated in synchronization with this timing. A signal read clock is applied to the solid-state image pickup device 15 of the line transfer system from the unit 25, the light is received with the illumination light before being shielded, and the photoelectrically converted signals are transferred and sequentially read out. 26 are written in the frame memory respectively. The signal taken into the video process unit 26 is subjected to signal processing and then separated into R, G and B color signals so that the subject image is displayed in color on the color TV monitor 27.

According to the first embodiment configured as described above, the filter used for illumination does not transmit only a single wavelength range but transmits light in a plurality of wavelength ranges to illuminate the subject. The illumination spectrum distribution of the white illumination lamp 19 can be efficiently illuminated with less loss than in the case of the conventional example. That is, the filter 23 in the first embodiment
In the case of using, it is possible to illuminate with the illumination light having the light transmission amount as shown in FIG. 6, so that the illumination light amount becomes 2 to 3 times as large as that in the conventional example shown in FIG. The S / N ratio of the signal is also improved as compared with the conventional example. Further, when illuminating the light through the filter 23, the illumination light including the green wavelength range is always performed, so that the green color signal G is always obtained, and the resolution is not deteriorated even for a subject having a large movement. A good color image can be obtained.

FIG. 7 shows a light source device according to a second embodiment of the present invention.
In the light source device 31 of this embodiment, the filter 32 is formed of stripe-shaped complementary color filters 32C, 32W, 32Y as shown in FIG.
A light-shielding plate 34 is provided adjacent to each of the slit-shaped transmission windows 33 having the width of the stripe and having three times the width of the stripe as one cycle. Each window 3 of this light shielding plate 34
Both ends in the direction perpendicular to the slit in 3 are fixed to the free end sides of the bimorph oscillators 35, 35 which are not fixed,
The other ends of these bimorph oscillators 35, 35 are fixed. Then, a stepwise wave drive signal is applied to the bimorph oscillators 35, 35 from the drive circuit 36, and the free end sides of both the bimorph oscillators 35, 35 can be vertically moved stepwise. Therefore, the light passing through the window 33 of the light shielding plate 34 is sequentially set to be in a state of being adjacent to the complementary color filters 32C, 32W, and 32Y in the state of being sequentially moved stepwise. The illumination lamp 19 is turned off for a short period of time when the light shielding plate 34 is moved stepwise, and signals are read from the solid-state image sensor during this period.

The lens 37 attached to the light shielding plate 34 adjacent to the light shielding plate 34 has a shape in which a cylindrical lens is connected in the up and down direction to be movable, collects the illumination light, and collects all of the illumination light. The window 33 is made transparent.

The operation and effect of the second embodiment are substantially the same as those of the first embodiment.

A magnet may be attached to the light shielding plate 34, and the magnet may be moved by a coil or an electromagnet so that it can function as in the second embodiment.

The filters 23 and 32 are not limited to the combination described above, and for example, instead of the white complementary color filter 23W, a magenta complementary color filter (referred to as 23M) that transmits light in the blue and red wavelength ranges is used. May be.

Complementary color filters 23C, 23M, 23 as the filter 23
The signal processing when C is used is performed as follows, for example. In the case of image pickup under the illumination of green and blue which has passed through the complementary color filter 23C, the image is written in the green and blue frame memories. The complementary color filter 23M is written in the blue and red frame memories. Further, in the case of illumination using the complementary color filter 23C, writing is performed in the red and green frame memories. However, focusing on the red frame memory, when writing in the illumination cycle for one frame (B + R)
Since the + (R + G) color signals are added, the red color signal 2R can be separated and output by subtracting the B + G signal and outputting.

Also by the above-mentioned signal processing, each color signal having a large S / N can be separated and output. In the process of subtracting and outputting B + G, B + G or the like may be written in another memory and then subtracted and output, or another method may be used. In the present invention, a green transmission filter may be used instead of the complementary color filter 23W.

Also, the types of filters are not limited to three types,
For example, in addition to the above 23C, 23W, and 23Y, four types such as a magenta complementary color filter may be used, or more types may be used. In short, a device using one or more complementary color filters belongs to the present invention.

In addition, the light-sensing characteristics of the solid-state image sensor 15 and the light guide 16
In terms of the transmission characteristics of (1), for example, when the illumination light in a specific wavelength range is weak, the illumination time may not be divided uniformly, but the ratio may be changed (the area of the filter may be used).

When the solid-state image pickup device 15 is arranged on the distal end side of the endoscope insertion portion, it is desirable to use the above-mentioned line transfer system that can be downsized, but the present invention is not limited to this, and frame transfer is also possible. Other types such as a system may be used. In this case, it is not necessary to turn off or shield the light during transfer.

Further, the present invention is not limited to one in which the solid-state image pickup device is arranged at the distal end side of the endoscope insertion portion, but can be applied to an image pickup tube or an endoscope having another built-in image pickup device. .
Further, the image pickup means is not limited to the one having the image pickup means built in the endoscope, and can be applied to an endoscope having an image guide formed of an optical fiber bundle and having the image pickup means attached to the eyepiece. It is a thing.

[Advantages of the Invention] As described above, according to the present invention, since the illumination light of three colors is sequentially illuminated to capture an image, the amount of light received by the image sensor can be increased and the S / N of each color signal output can be increased. In addition, since all the image pickup elements are used for each color, it is possible to obtain a bright, contrasted color image having excellent resolution.

In addition, a stripe-shaped three-color filter and a light-shielding plate in which transmitted light is formed with three times the stripe width as one cycle are used.
Since the light source device is configured to move the light shielding plate in small steps, it is possible to switch a plurality of colors having a large amount of light and to switch the filters within a video blanking period that is short in time. Further, the light source device can be downsized as compared with the rotary filter system and the multiple light source system, and it is mechanically strong.

[Brief description of drawings]

1 and 2 relate to a conventional example, FIG. 1 is a front view showing a filter in the conventional example, and FIG. 2 is an explanation showing an amount of light transmitted to the subject side when using FIG. FIGS. 3 to 6 relate to a first embodiment of the present invention,
FIG. 3 is an explanatory view showing the structure of the first embodiment, and FIG.
FIG. 5 is a front view showing a filter used in an embodiment, FIG. 5 is a characteristic view showing a transmission characteristic of the filter, FIG. 6 is an explanatory view showing a light transmission amount of the filter, and FIGS. FIG. 7 is an explanatory view showing a light source device in the second embodiment, FIG. 8 is a perspective view showing a filter in the second embodiment, and FIG. 9 is a bimorph oscillator moving a light shielding plate according to the second embodiment. It is a perspective view shown. 11 ... Endoscope, 13 ... Tip part 14 ... Objective lens, 15 ... Solid-state image sensor 16 ... Light guide, 18, 31 ... Light source device 19 ... Illumination lamp, 22 ... Motor 23, 32 ...... Filter 24 ...... Driving circuit 25 ...... Synchronization signal generator 26 ...... Video processing unit 27 ...... TV monitor 33 ...... Window 34 ...... Shading plate 35 ...... Bimorph vibrator 37 ...... Lens

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-51-65962 (JP, A) JP-A-55-38790 (JP, A) JP-A-58-46926 (JP, A) Actual development Sho-55- 53803 (JP, U) Actually open 55-151011 (JP, U) Special public 49-49379 (JP, B1) Actual public 46-460 (JP, Y1)

Claims (1)

[Scope of utility model registration request] 1. An endoscope in which an object is sequentially illuminated with illumination light of different wavelength ranges and an image is picked up by an image pickup means, and a filter main body formed of stripe-shaped three-color filters and a filter main body adjacent to the filter main body. And a light-shielding plate having slit-shaped transmission windows each having the stripe width of the filter body formed with three times the stripe width as one cycle, and the light-shielding plate in a direction perpendicular to the slits in each window of the light-shielding plate. An image pickup device comprising: a movable unit that moves the plate in a step shape; and a cylindrical lens that is formed in a shape in which the light shielding plate is vertically connected and that is adjacent to the light shielding plate. Endoscope using.