JPH0738702B2 - Endoscope - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an endoscope including a solid-state image sensor of an interline transfer system at a tip portion thereof, and more particularly, to improvement of resolution improving means of the solid-state image sensor.

[Prior art]

The size of the solid-state imaging device used for an endoscope is limited. Therefore, the number of pixels of the solid-state image sensor is limited by itself, and there is a problem that sufficient resolution cannot be obtained.
As a means for improving the resolution, there is one in which the chip of the solid-state imaging device is vibrated in the frame direction in the optical axis direction, but the above is for improving the resolution of the image guide of the endoscope. The solid-state image sensor itself does not improve the resolution. Therefore, it cannot be applied to a type that does not use an image guide fiber, for example, a type that mounts a solid-state image sensor on the tip of an endoscope and transmits only an image pickup signal to the outside. Moreover, the vibration width,
There is a problem in that there is a problem in the accuracy of the cycle and the durability is also poor.

〔Purpose〕

The object of the present invention is to provide a small and lightweight solid-state image pickup device in which the resolution of the solid-state image pickup element is sufficiently high, there is no mechanical vibration part, there is no problem in accuracy and durability, and highly reliable operation can be expected. To provide an endoscope.

〔Overview〕

The present invention is characterized by having the following constitution in order to achieve the above object. The present invention relates to an endoscope having an interline transfer type solid-state image sensor in which pixels and transfer lines are alternately arranged in a horizontal direction at a distal end portion, and an electro-optical element is provided in front of a light incident side of the solid-state image sensor. , A predetermined control voltage is applied to this electro-optical element to variably control the refractive index, and the position of the optical image formed on the solid-state image sensor is set to 1/2 of the distance between pixels in the solid-state image sensor. It is characterized in that it is moved in the horizontal scanning direction.

〔Example〕

FIG. 1 is a diagram showing an embodiment in which the present invention is applied to an imaging device for an endoscope. In the figure, reference numeral 1 denotes an endoscope, and an objective lens 2 is attached to the tip of an insertion portion 1A of the endoscope 1. An image pickup body 4 is arranged so as to face the objective lens 2 via an electro-optical element 3 described later. A signal of an optical image photoelectrically converted by the image pickup body 4 is sent to a camera controller (not shown) via a signal transmission cable 5 to be a video signal. This video signal is guided to the eyepiece 1B by the signal transmission cable 6, and the CR provided in the eyepiece 1B
Projected by T7. Thus, the observed portion can be observed on the screen displayed on the CRT7.

On the other hand, a cover lens 8 is mounted on the side of the objective lens 2 at the tip of the insertion section 1A, and an illumination light guide fiber 9 is provided so that one end faces the cover lens 8. The other end of the light guide fiber 9 is led to a light source device for an endoscope (not shown).

FIG. 2 is a diagram showing in detail the objective lens 2, the electro-optical element 3, and the image pickup body 4 shown in FIG.

As shown in FIG. 2, the electro-optical element 3 is provided in front of the light-incident side of the image pickup unit 4 and inclined with respect to the optical axis. This electro-optical element 3 is a transparent dielectric flat plate having an electro-optical effect.
It has a structure in which transparent thin film electrodes 11 and 12 are vapor-deposited on both front and back surfaces of 10. The transparent dielectric flat plate 10 is made of, for example, lithium neobiate LiNbO ₃ , and titanium Ti is uniformly distributed and diffused. The transparent thin film electrodes 11 and 12 are made of, for example, SnO ₂ or InO ₃ . The transparent thin film electrodes 11 and 12 are lead wires 13 and 14.
Is connected to the output terminal of the DC voltage applying device 15 as the control voltage applying means.

On the other hand, the image pickup body 4 is a solid-state CCD composed of an interline transfer system, in which a plurality of photo-detecting elements are arranged in a matrix, an optical image is converted into an electric signal, and the electric signal is scanned and taken out. The image pickup device 16 and a mount 17 that holds the solid-state image pickup device 16 are included.

FIG. 3 is a diagram showing a specific configuration of the solid-state imaging device 16.
In FIG. 3, 18 is a photodiode group, 19 is a vertical CCD that vertically transfers the signal charges from the photodiode group 18, 20 is a horizontal CCD that horizontally transfers the charges transferred by the vertical CCD, and 21 is The output section sends out the electric charges transferred by the horizontal CCD as an output signal.

Next, the operation of the present apparatus configured as described above will be described. In the state where the control voltage is not applied to the electro-optical element 3 from the DC voltage applying device 15, the refractive index of the electro-optical element 3 is relatively small, and the optical paths A and B are as shown by the solid line in FIG.
When a control voltage is applied to the electro-optical element 3 from the DC voltage applying device 15, an electric flux corresponding to the dielectric constant in the transparent dielectric plate 10 is generated, and the refractive index increases according to the magnitude of the electric flux density. , The optical paths A and B are as shown by the broken lines in FIG. If the applied voltage is increased, there is an electric flux density and the refractive index increases. Here, the solid-state imaging device 16 due to the deviation of the optical paths A and B
The positional deviation of the optical image formed above is L / 2 when the distance between the photodiodes in the horizontal scanning direction shown in FIG. 3 is L.
Is set to. Further, the voltage application from the DC voltage application device 15 to the electro-optical element 3 is alternately and periodically performed. It is assumed that this cycle is synchronized with the frame frequency at which one image is obtained. (30Hz in NTSC system) Therefore, when the voltage is not applied, light is incident on the solid-state image sensor 16, and the electric charges at that time are transferred vertically by the vertical signal transfer CCD 19 and further transferred horizontally by the horizontal signal transfer CCD 20. Then, when voltage is applied during the period of reading information from the output unit 21, light is incident on the position of the solid-state image sensor 16 which is shifted by L / 2 from that when no voltage is applied. Then, the charges at this time are read out in the same manner as above.
By doing so, in the image forming state at the position where the voltage is not applied for the first time, the image forming portion that is not received by the photodiode group 18 because it is located in the vertical signal transfer CCD 19 is L / It will be offset by 2 horizontally. As a result, the resolution is doubled in the horizontal direction.

In the device shown in the above embodiment, since the electro-optical element 3 is interposed between the objective lens 2 and the image pickup body 4, the optical system may have the same size as that of the conventional one, and it can be used as it is in the conventional image pickup device. Easy to apply.

In this embodiment, the resolving power can be increased only by providing a means for applying a control voltage to the electro-optical element 3, so there is no need to perform mechanical vibration as in the conventional case. Therefore, there is no problem in terms of accuracy and durability of vibration operation, and highly reliable operation can be expected.

FIG. 4 is a view corresponding to FIG. 2, showing the flow of the image pickup section of another embodiment of the present invention. In this embodiment, the electro-optical element 3 is arranged further in front of the objective lens 2. According to this embodiment, the optical system is slightly larger than that of the above embodiment, but the inclined surface of the electro-optical element 3 can be made smaller than that of the above embodiment.

That is, the angle between the incident ray and the outgoing ray in the objective lens 2 with respect to the optical axis is much larger in the latter case. Therefore, in the case of the above-mentioned embodiment, since the light beam incident on the electro-optical element 3 is the light beam emitted from the objective lens 2 having a large angle with respect to the optical axis, the image formation is predetermined unless the inclination angle of the electro-optical element 3 is increased. Does not move to position. In this respect, in the case of the present embodiment, the light beam incident on the electro-optical element 3 is the light beam incident on the objective lens 2 having a small angle with respect to the optical axis. Move to a predetermined position. It should be noted that this embodiment has an advantage that the defocusing of the image and the distortion of the image on the light receiving surface of the solid-state image sensor 16 are reduced. That is, there is an advantage that a clear image can be obtained with less astigmatism, spherical aberration and the like as compared with the above-mentioned embodiment.

〔The invention's effect〕

According to the present invention, the electro-optical element is provided in front of the light incident side of the solid-state image sensor, and a control voltage is applied to the electro-optical element to shift the image forming position of the light-receiving surface of the solid-state image sensor to a predetermined position. It is possible to provide a solid-state image pickup device which can make the resolution of the solid-state image pickup device sufficiently large, has no mechanical vibration portion, has no problem in terms of accuracy and durability, and can be expected to have reliable operation for a long period of time. .

[Brief description of drawings]

1 to 3 are views showing a first embodiment of the present invention, FIG. 1 is a side sectional view schematically showing the entire structure, and FIG. 2 is a view showing the structure of an imaging unit. FIG. 3 is a plan view showing a schematic structure of a solid-state image pickup device, and FIG. 4 is a view showing a structure of an image pickup section according to a second embodiment of the present invention. 1 ... Endoscope, 1A ... Insertion part, 1B ... Eyepiece part, 2 ... Objective lens, 3 ... Electro-optical element, 4 ... Imaging body, 5,6 ...
… Signal transmission cable, 7 …… CRT, 8 …… Cover lens, 9 …… Light guide fiber for illumination, 10 …… Transparent dielectric plate, 11,12 …… Transparent thin film electrode, 13,14… Lead wire, 15 ... DC voltage application device, 16 ... Solid-state image sensor, 17
...... Mount, 18 …… Photodiode group, 19 …… Vertical signal transfer CCD, 21 …… Output section,

Claims (1)

[Claims] 1. An interline transfer type solid-state imaging device in which pixels and transfer lines are alternately arranged in a horizontal direction, an endoscope insertion section having the solid-state imaging device at a tip, and a light incident side of the solid-state imaging device. The position of the optical image formed on the solid-state imaging device by changing the refractive index by applying a voltage in front of the optical axis is 1/1 / the distance between pixels in the solid-state imaging device. An endoscope comprising: a flat plate-shaped electro-optical element that moves by 2 in the horizontal scanning direction; and a control voltage applying unit that applies a control voltage to the electro-optical element.