JPH0789177B2 - Image forming optics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming optical system which improves image quality by relatively vibrating an object image and a fiber bundle in a direction perpendicular to an optical axis.

[Conventional technology]

In an optical device that receives an object image on one end surface of an image guide composed of a large number of fibers bundled like an endoscope and transmits this to the other end surface for observation, the relative relationship between the object image and the incident end surface of the image guide. If the position is changed minutely (about the thickness of the fiber) in a short period (to the extent that the afterimage effect of the eye can be used) in the direction perpendicular to the optical axis, the image of the image observed at the exit end face of the image guide is improved. Is known (for example, S.Kapany “Fibers Optics” ACA-DEMIC P
RESS 1967).

Conventionally, attempts have been made to improve the image quality of an endoscope (fiberscope) by utilizing this phenomenon. For example, the one disclosed in Japanese Patent Laid-Open No. 57-46211 has a permanent magnet fixed to the outer periphery of one of the objective lenses arranged in front of the entrance end face of the image guide, and this is used as an image guide. It is connected to a fixed AC solenoid via a cushion. Then, the lens is rotated around an axis perpendicular to the optical axis by the action of an AC magnetic field generated by applying an AC current to the AC solenoid, and the object image is vibrated on the incident end face of the image guide. Then
This improves the image quality.

On the other hand, the exit side of the image guide is also provided with the same structure to vibrate the image exiting the image guide in synchronization with the entrance side to prevent the observed image from being blurred due to the vibration of the lens. .

[Problems to be solved by the invention]

However, when the lens is rotated about an axis perpendicular to the optical axis, the ridge line portion of the outer peripheral portion of the lens travels in the outer diameter direction when the lens is tilted. There must be some extra space in the direction beforehand. For this reason, the distal end portion including the objective lens of the endoscope becomes thick, and this is a problem in the endoscope in which it is desirable to be as thin as possible.

In view of this, the present invention provides an image forming optical system in which the image quality is improved without making the distal end portion of the endoscope thick.

[Means and Actions for Solving Problems]

In the image forming optical system according to the present invention, a plurality of optical elements in which at least one of the entrance surface and the exit surface is inclined with respect to the optical axis are arranged in front of the entrance end surface of the image guide. Then, at least one of them is vibrated back and forth along the optical axis to change the distance between the adjacent optical elements. As a result, the height difference between the incident light and the emitted light to the optical system including the optical element having the inclined surface fluctuates, and the object image vibrates in the direction perpendicular to the optical axis on the incident end surface of the image guide. Become.

That is, the image forming optical system according to the present invention realizes the movement of the relative position between the object image and the image guide in the direction perpendicular to the optical axis only by moving the optical element in the optical axis direction.

〔Example〕

FIG. 1 shows the first embodiment, and a prism optical system including a vibrating prism 3 and a fixed prism 4 is arranged between the objective lens 1 and the incident end surface 2a of the image guide 2. The entrance surface 3a of the vibrating prism 3 is perpendicular to the optical axis, and the exit surface 3b is inclined. The exit surface 4b of the fixed prism 4 is perpendicular to the optical axis, and sandwiches the cover glass 5 to be joined to the entrance end surface 2a of the image guide 2,
The entrance surface 4a is inclined parallel to the exit surface 3b of the vibration prism 3. One end of a rod-shaped piezoelectric element actuator 6 is fixed to the outer peripheral portion of the vibration prism 3. The other end of the actuator 6 is fixed at an appropriate position on the endoscope body (not shown).

When an alternating voltage is applied to the piezoelectric element actuator 6 from a power source (not shown), the piezoelectric element actuator 6 expands and contracts according to the voltage change, and accordingly, the vibrating prism 3 vibrates back and forth along the optical axis.

FIG. 2 is a principle diagram of the first embodiment. As shown in FIG. 2, a light beam is refracted upward by the exit surface 3b of the vibrating prism 3 when it exits from the vibrating prism 3, and when it enters the fixed prism 4, its entrance surface.
It is refracted again at 4a and becomes parallel to the original light. Fixed prism 4
Inject. Due to this refraction effect, when the distance between the prisms 3 and 4 changes, the difference between the height of the incident light beam and the height of the emitted light beam of the prism system changes. The amplitude of vibration of the actuator 6 is Δx, the refractive index of both prisms is n, the tilt angle of the exit surface 3b of the vibrator prism 3 (= the tilt angle of the entrance surface 4a of the fixed prism 4) is θ, and the exit angle of the vibrator prism 3 is If θ ′, the amplitude Δy of the optical axis that exits the prism system (the amplitude of the image on the image guide entrance end face 2a), Given in. Therefore, the size of the piezoelectric element actuator 6, the refractive indexes of the prisms 3 and 4, and the inclination angle of the surface may be determined so that Δy has a desired value.

If the image vibrates on the incident end face 2a of the image guide 2 due to the vibration of the vibrating prism 3, the image observed on the eyepiece side also vibrates and becomes difficult to see if it is left as it is, so it is desirable to compensate for this. In the conventional example, the exit end of the image guide 2 is also provided with a vibrating mechanism having the same structure as the entrance end, and the vibration on the entrance side is canceled by vibrating with the same amplitude in synchronization with the entrance side. Also in the present invention, the vibration mechanism described above as shown in FIG. 3 may be provided between the exit end of the image guide 2 and the eyepiece lens 20. Moreover, since the exit side of the image guide 2 does not usually need to be downsized,
In this portion, not only the structure disclosed in the conventional example but also the image guide exit end may be directly vibrated perpendicularly to the optical axis. That is, it is possible to adopt various configurations as shown in FIG. 4 (a) is for rotating the prism 7 between the eyepiece 20 and the image guide 2 by the motor 8, gear 9, and support frame gear 10, and FIG. 4 (b) is for the eyepiece 20 and image. The inclined parallel flat glass plate 19 between the guide 2 and the guide 2 is rotated by the motor 8, the gear 9, and the support frame gear 10 or is eccentrically rotated, that is, vibrated. The part is eccentrically rotated, that is, vibrated by a motor 8, a gear 9, and an eccentric gear 11.

FIG. 5 shows a second embodiment, in which an objective lens 1 has a structure in which a vibrating prism 3'is sandwiched between two fixed prisms 4 ', 4. Fixed prism 4 '
The entrance surface 4'a is perpendicular to the optical axis and the exit surface 4'b is inclined, and the entrance surface 4a of the fixed prism 4 is tilted in the opposite direction to the exit surface 4'b with respect to the optical axis. And the exit surface 4b is vertical. The entrance surface 3'a of the vibrating prism 3'is inclined parallel to the exit surface 4'b of the fixed prism 4'and the exit surface 3'b is inclined parallel to the entrance surface 4a of the fixed prism 4.

FIG. 6 is a principle diagram of the second embodiment. As shown in the figure, the light beam is refracted upward when it emerges from the fixed prism 4 ',
When entering the vibrating prism 3 ', it is refracted at the incident surface 3'a and becomes parallel to the original light, and when it exits the vibrating prism 3', it is refracted downward, and when entering the fixed prism 4, its incident surface 4a. The light is refracted by and is again parallel to the original light and is emitted from the fixed prism 4. In this case, the relationship between the vibration amplitude Δx of the piezoelectric element actuator 6 and the amplitude Δy of the optical axis emitted from the prism system is Becomes However, n, θ and θ ′ are the same as in the first embodiment.

In the case of this example, the amplitude Δy is amplified by the magnification β in the optical system after the fixed prism 4, so that the amplitude of the image on the incident end face 2a of the image guide 2 is β · Δy. Therefore, the amount of movement of the image which is 2β times that in the case of the first embodiment can be obtained.
If the amplitudes of the images are the same, the amplitude of the piezoelectric element actuator 6 can be set to Δx / 2β, and as a result, it becomes possible to use a piezoelectric element actuator having a short length, and an endoscope having a short rigid portion can be realized.

FIGS. 7 (a) and 7 (b) respectively show the structure and principle of the third embodiment, which has a structure in which a vibrating prism 3'is sandwiched between two fixed prisms 4 ', 4. Exit surface 4'b of the fixed prism 4'and the entrance surface 3'a of the vibrating prism 3 '.
The exit surface 3'b of the vibrating prism 3'and the entrance surface 4a of the second fixed prism 4 are parallel to each other, but the normal line of the entrance surface 3'a of the vibrating prism 3'is The normals to the exit surface 3'b of the prism 3'are arranged in planes perpendicular to the paper surface.

In this case, the image vibration is Δy on the paper surface and Δz in the direction perpendicular to the paper surface. However, since Δy and Δz have the same phase, the image vibration is performed on a straight line having an inclination angle.

FIG. 8 shows a main part of a modification of the third embodiment, which is obtained by cutting the vibrating prism 3'into a plane perpendicular to the light beam and dividing it into two vibrating prisms 3'A and 3'B. is there. When the first vibrating prism 3'A is moved back and forth, the image moves up and down in the plane of the paper, and when the second moving prism 3'B is moved back and forth, the image moves in the direction perpendicular to the plane of the paper. If the angular frequency of vibration of the first vibrating prism 3′A is ω ₁ and the angular frequency of the second vibrating prism 3′B is ω ₂ , Δx ₁ sin (ω ₁
t + φ ₁ ), Δx ₂ sin (ω ₂ t + φ ₂ ), the angular frequencies ω ₁ and ω _{2 of} each vibration, and the initial phase (relative positional relationship between the two vibration prisms 3′A and 3′B) φ Depending on how ₁ and φ ₂ are decided, the movement locus of the light beam that exits the prism system is a straight line, a circle,
It may have various shapes such as an ellipse.

FIG. 9 shows a fourth embodiment, which is mounted on the eyepiece of the endoscope 12 and is used before and after the image guide 14 of the viewing scope 13 used for viewing the same image by a plurality of people. The image vibrating mechanism as described above is provided. Viewing Scope 13
Has a beam splitter 15, and an imaging lens 16, a fixed prism 4, a vibrating prism 3, an image guide 14, a vibrating prism 3, a fixed prism 4, and an eyepiece lens 17 are sequentially arranged on the optical path branched by the beam splitter 15. It is set up. The exit end surface of the image guide 2 in the endoscope 12 is imaged on the entrance end surface of the image guide 14 by the eyepiece lens 18 and the imaging lens 16, so that the beam splitter 15 and the image guide 14 are incident on this imaging optical path. If the image vibrating mechanism is arranged between the end faces and the image is vibrated on the incident end face of the image guide 14, the image quality is improved. Moreover, since the mesh structure of the fiber on the end face of the image guide becomes invisible by applying the vibration, the respective mesh structures of the exit end face of the image guide 2 of the endoscope 12 and the entrance end face of the image guide 14 of the viewing scope 13 interfere with each other. It is also useful for removing moire that occurs as a result.

FIG. 10 shows a fifth embodiment, in which two vibrating prisms 3 are arranged between three fixed prisms 4 and both vibrating prisms 3 are moved synchronously in the same direction. As a result, the amount of movement of the image can be doubled, and the amplitude of the piezoelectric element actuator can be reduced.

In each of the above-mentioned embodiments, it is not necessary that the inclined surfaces of the prisms facing each other be parallel to each other. However, if the angle is changed too much, astigmatism will be generated in the air gap, so it may be appropriately determined in consideration of it. Also, for example, in the first embodiment, the moving prism 3
If the entrance surface 3a is not perpendicular to the optical axis, it becomes a perspective as shown in FIG. 11, so the angle of this surface may be variously tilted depending on the application. Of course, as shown in FIG. 12, the lens may be divided into two and used in place of the prism.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of an image forming optical system according to the present invention, FIG. 2 is a principle diagram of the first embodiment, and FIG. 3 is a schematic sectional view showing an application example of the first embodiment. 4 (a), (b),
(C) is a figure which shows various structures of the eyepiece part of the said application example, FIG. 5 is sectional drawing of 2nd Example, FIG. 6 is the principle figure of 2nd Example, FIG. 7 (a) and (B) is a sectional view showing the structure of the third embodiment and a perspective view showing the principal part of the principle, FIG. 8 is a perspective view showing the essential part of a modified example of the third embodiment, and FIG. 9 is a fourth embodiment. A schematic cross-sectional view of an example, FIG. 10 is a schematic cross-sectional view of a main part of the fifth embodiment,
FIG. 11 is a schematic sectional view of a modification of the first embodiment, and FIG. 12 is an explanatory view of another modification. 1 ... Objective lens, 2 ... Image guide, 3, 3 '...
Vibration prism, 4,4 '... Fixed prism, 5 ... Cover glass, 6 ... Piezoelectric actuator, 7 ... Prism, 8 ... Motor, 9 ... Gear, 10 ... Support frame gear, 11
…… Eccentric gear, 12 …… Endoscope, 13 …… Viewing scope,
14 …… Image guide, 15 …… Beam splitter, 16…
… Imaging lens, 17,18,20 …… Eyepiece, 19 …… Inclined parallel flat glass plate.

Claims (4)

[Claims] 1. An image forming optical system for forming an image of an object on an optical fiber bundle by an objective lens provided at a tip portion of an endoscope, a first prism having an exit surface inclined with respect to an optical axis, A prism system including at least a second prism having an incident surface inclined with respect to the optical axis is arranged on the optical axis, and at least one of the first prism and the second prism is inclined along the optical axis. An image forming optical system in which an image of an object on an optical fiber bundle is vibrated without being vibrated in a direction perpendicular to the optical axis. 2. The image forming optical system according to claim 1, wherein the exit surface of the first prism and the entrance surface of the second prism are parallel to each other. 3. The exit surface of the second prism is inclined with respect to the optical axis such that the normal line thereof is in the same plane as the normal line of the entrance surface of the second prism, and the exit surface of the second prism is on the exit side. The third prism having an incident surface parallel to the exit surface is arranged, and the third prism is arranged.
The image forming optical system described in 1. 4. The exit surface of the second prism is inclined with respect to the optical axis so that its normal line is not in the same plane as the normal line of the entrance surface of the second prism, and the exit surface side of the second prism. The image forming optical system according to claim (1) or (2), characterized in that a third prism having an entrance surface parallel to the exit surface is disposed in the image forming optical system.