JPH01319709A - Device for adjusting incident angle of light beam - Google Patents

Abstract

PURPOSE:To facilitate the angle adjustment at the time of casting a light beam through a condenser lens to a light transmission fiber by disposing a transparent rod to the incident side of the condenser lens, holding the rod in such a manner that the normal direction of the end face thereof is freely adjustable and adjusting the angle of inclination of the transparent rod. CONSTITUTION:Since both ends 16a, 16b of the transparent rod 16 are parallel planes, the transparent rod has no divergent and convergent properties and the main ray of the emitted light beam is parallel with the main ray of the incident light beam 10. Since the parallel exit light thereof is condensed by the condenser lens 12, the position of the focus thereof does not depends on the angle of inclination of the transparent rod 16 and is always at one point on the optical axis. The incident angle theta to the light transmission fiber 14, therefore, changes and can be easily adjusted to the optimum conditions by adjusting the angle alpha of inclination of the transparent rod 16 as far as the incident end face 14a of the fiber 14 exists in said position.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for using a light beam of a gas laser, a semiconductor laser, etc.
Regarding a device for efficiently inputting a light beam into an optical transmission fiber through a condensing lens, in more detail, it is an incident angle adjustment device in which a transparent rod whose end surfaces are parallel planes is arranged in a predetermined direction on the incident side of a condensing lens. It is related to the device.

[Prior Art] In the conventional art, as shown in FIG. 4, a light beam lO generated from a gas laser, a semiconductor laser, etc.
The light is focused and sent to the optical transmission fiber 14.

In order for the light beam 10 to enter the optical transmission fiber 14 efficiently, the condensing lens 12 and the optical transmission fiber 14 must be arranged with high accuracy with respect to the light beam 10, and the accuracy affects the incidence efficiency. I will do it.

One of the causes of deterioration of the incidence efficiency is that the principal ray of the light beam incident on the optical transmission fiber 14 is not perpendicular to the input end surface 14a of the optical transmission fiber 14.

Therefore, the optical transmission fiber 14 has an input end face 14a.
must be adjusted so that it is located on the optical axis and approximately at the focal point of the condensing lens 12, and the normal direction of the incident end surface 14a is parallel to the optical axis 0-o. 14 will be installed by moving the position and direction.

[Problems to be Solved by the Invention] Incidentally, the incident end surface 14a of the optical transmission fiber 14 is not necessarily cut completely at right angles to the central axis of the optical transmission fiber 14. Therefore, even if the optical transmission fiber 14 Even if it is installed along the optical axis 0--0, there is a possibility that the normal direction of the incident end surface 14a is inclined at a certain angle with respect to the optical axis 0-0.

There is a high possibility that the incidence efficiency into the optical transmission fiber will decrease due to this inclination. Especially when a single mode fiber is used as the optical transmission fiber 14, the aperture angle of the optical transmission fiber 14 is about 0.1. is very small, so the adjustment precision of the principal ray of the light beam incident on it must be higher.

As mentioned above, since the input end face 14a is not necessarily perpendicular to the central axis of the optical transmission fiber 14, an optimal coupling state can be obtained even if the central axis of the optical transmission fiber 14 is aligned with the optical axis. Not necessarily. On top of that,
In an optical system as shown in FIG. 4, it is very difficult to adjust the attachment of the optical transmission fiber 14 by changing the angle.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
An object of the present invention is to provide a light beam incident angle adjustment device that can easily adjust the angle when a light beam is incident on an optical transmission fiber through a condensing lens, thereby increasing the incidence efficiency.

[Means for Solving the Problems] As shown in FIG. 1, the present invention, which can achieve the above object,
This is an incident angle adjusting device for condensing the light with a condensing lens 12 and making it incident on the optical transmission fiber 14, and a transparent rod 16 is arranged on the incident side of the condensing lens 120.

Here, the transparent rod 16 is made of a material that is transparent to the wavelength of the incident light beam 10, and its both end surfaces 16
a and 16b are each flat and parallel to each other. This transparent rod 16 has its end surfaces 16a, 1
It is held adjustable so that the normal direction of 6b can be freely set. That is, if the oblique angle between this normal direction and the optical axis 0-0 is α, the angle α is held so as to be freely variable.

[Operation] When the transparent opening 7 and 16 are arranged at an angle α with respect to the light beam O, both end surfaces 16a and 16b of the transparent rod 16
are mutually parallel planes, so the chief ray of the emitted light beam becomes parallel to the chief ray of the original light beam 10 at a position separated by a distance δ from the original light beam 10. The amount of positional deviation δ of the principal ray of the light beam is expressed by the following equation, where a is the length of the transparent loft 16 and n is the refractive index.

, δ-=a-tan(α-5in-'(sin α/n)
)...(1) This light beam enters the condensing lens 12 in parallel at a distance δ from its center, and focuses at the incident end face 14a of the optical transmission fiber 14 on the optical axis 0-0. tie. Assuming that the focal length of the condensing lens 12 is 1, the angle of incidence θ on the optical transmission fiber 14 is expressed by the following equation.

θ=sin-'(δ/f)-(
2+ Therefore, from the +1i formula and the formula (2) above, it can be seen that by changing the inclination angle α of the transparent rod 16, the incident angle θ to the optical transmission fiber 14 can be changed.

In the present invention, since both end surfaces of the transparent rod 16 are parallel planes as described above, the transparent rod 16 does not have diverging or converging properties, and the principal ray of the emitted light beam is different from the principal ray of the incident light beam 10. become parallel. Since the parallel emitted light is condensed by the condenser lens 12, the position of its focal point is always at one point on the optical axis, regardless of the inclination angle of the transparent rod 16. Therefore, as long as the incident end face 14a of the optical transmission fiber 14 is at that position, the incident angle θ to the optical transmission fiber 14 can be changed by adjusting the inclination angle α of the transparent loft 16, and the angle of incidence θ to the optical transmission fiber 14 can be easily adjusted to the optimum condition. becomes possible.

[Example] How accurately the angle of incidence θ to the optical transmission fiber 14 can be adjusted depends on how accurately the inclination angle α of the transparent rod 16 can be adjusted. FIGS. 2 and 3 show an example of a specific support structure for the transparent rod 16. FIG.

The transparent rod 16 has a round rod shape as a whole, and has cutout portions 16c at right angles to each other on the outer periphery on the output side.

16d is formed. The transparent rod 16 is swingably held by a fulcrum 18 at its end on the incident side. This fulcrum 18 has a structure similar to, for example, a gyroscope, and holds the output side end so as to have degrees of freedom in the X-axis direction and the Y-axis direction.

An adjustment point is provided on the exit side of the transparent rod 16. This adjustment point is a three-point support mechanism consisting of adjustment screws 20a and 20b that abut the notches 16c and 16d, respectively, and a spring 22 located on the opposite side thereof. A fixing screw 24 is provided inside the spring 22.

For example, by rotating the adjustment screws 20a, they move forward or backward by a distance, and the end of the transparent rod 16 changes against the force of the spring 22 in the Y-axis direction. This allows the inclination angle α of the transparent rod 16 to be adjusted,
Once the adjustment is completed, the holding screw 24 can be rotated and brought into contact with the outer peripheral surface of the transparent rod 16 to fix it in that position.

Now, the distance C between the fulcrum 18 and the adjustment point at the transparent opening 7 door 16 is 80m5, and the screws 20a and 20 at the 11th node are
If the pitch of b is 0.5-1, and the rotation angle of the adjustment screw can be adjusted in 5 degree increments using a screwdriver, etc., then the resolution in the axial direction of the screw is:

is bc =0.5・(5/360) =6. The inclination angle α of the transparent rod 16 when the adjustment point changes by this resolution S, which is 94X10-1 (-1), is α(=jan-' (b c / c ) = tan-
'(6,94X 10-"/80)=4.97X1
0-3 (degrees). At that time, the amount of positional deviation δ of the principal ray of the light beam in FIG.
5. If the length a is 90Il#l, δc-2.65X
10-' (Ilm), where the angle of incidence θ on the optical transmission fiber 14 in FIG.
Then, it becomes as follows.

θc = sin-' (δc/f)-3,37X
10 bow (degrees) This value is s, ss x to-' when expressed in terms of the aperture angle, and is sufficiently small even for the aperture angle of 0.1 of the optical transmission fiber 14. Therefore, it can be adjusted with a sufficiently high precision by adjusting the adjustment screw. Adjustment is possible.

Although a preferred embodiment of the present invention has been described in detail above, the holding mechanism is not limited to the above-described holding mechanism as long as the transparent rod is held in an adjustable angle. Considering the actual production and use, the length of the transparent rod is 400 mm.
m5 or less, the focal length of the condenser lens is preferably 11 or more, and in the structure supported by the fulcrum and adjustment point as described above, it is desirable to set the interval between them to 10 mm or more. However, in order to produce a certain amount of positional deviation δ of the principal ray, the transparent rod must have a long distance between its both end faces and must not be in the form of a thin plate. In other words, the transparent rod only needs to have a certain distance between both end faces, and its cross-sectional shape is not limited to a cylindrical shape but may be a polygonal column or the like.

[Effects of the Invention] As described above, the present invention arranges the transparent rod on the incident side of the condensing lens and holds it so that the normal direction of the end face can be adjusted freely. Therefore, the inclination angle of the transparent rod can be adjusted. By doing so, the angle of incidence at the input end face of the optical transmission fiber can be aligned perpendicularly, which has the excellent effect of preventing deterioration of the incidence efficiency.

In the present invention, since both end surfaces of the transparent rod are flat, they can emit light and
Since it has no convergence and both end faces are arranged in parallel, the principal ray of the outgoing light beam is parallel to the principal ray of the incident light beam, so the position of the focal point by the condenser lens is always constant. Become. Therefore, as long as the position of the condensing lens and the input end face of the optical transmission fiber is precisely aligned, the maximum amount of incident light can be easily adjusted by simply adjusting the inclination of the transparent rod according to the angle of the input end face. can do.

In particular, as shown in the example, if a three-point support mechanism is adopted in which one end is swingably held by a fulcrum, and the other end is position-adjustable in two axes perpendicular to the optical axis using adjustment screws. The inclination angle of the transparent rod can be adjusted by moving the screw back and forth minutely, so all you have to do is measure the amount of light received by the optical transmission fiber and rotate the adjustment screw to obtain the maximum amount of light. This has the effect that even an unskilled person can easily and quickly adjust the angle of incidence without requiring any skill.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the basic configuration of a light beam incident angle adjusting device according to the present invention, FIG. 2 is a side view showing an example of the support structure of the transparent rod, and FIG. 3 is a front view thereof. FIG. 4 is an explanatory diagram showing the prior art. 10... Light beam, 12... Condensing lens, 14...
・Optical transmission fiber, 16...Transparent rod, 18...
-Fully point, 20a, 20b...adjustment screw, 22...spring. Patent applicant Nippon Sheet Glass Co., Ltd.

Claims (1)

[Claims] 1. A device for making a light beam enter an optical transmission fiber through a condensing lens, in which a transparent rod is arranged on the incident side of the condensing lens, and both end surfaces of the transparent rod are parallel planes. What is claimed is: 1. An incident angle adjusting device for a light beam, characterized in that the device is held so that the normal direction of its end face can be freely adjusted. 2. The transparent rod according to claim 1, wherein one end of the transparent rod is swingably held by a fulcrum, and the other end is supported by a three-point support mechanism adjustable in two directions perpendicular to the optical axis. Light beam incident angle adjustment device.