DD243123A1 - ARRANGEMENT FOR INPUTING A LASER BEAM INTO A GLASS FIBER - Google Patents

Abstract

Arrangement for coupling a laser beam into a glass fiber. An easy-to-use, low-loss and accurate adjustment is realized in that all parts of the support of the optical fiber to the optical axis are rotationally symmetrical and between the focusing lens and glass fiber rotatable about the optical axis and tiltable about an axis perpendicular to the optical axis, for the laser light Passive adjustment plate is arranged. Fig. 2

Description

The adjusting plate is mounted in a rotatable drum 13 and is rotated by a set screw 10. Another set screw 11 realizes a horizontal deflection of a plate connected to the, equipped with a return spring 12 lever and thus a tilt about tilt axis 5. The screw 11 moves in a semi-circular expansion in the housing upon rotation of the screw 10 with. In Fig. 3, the vertical offset is shown to a plate piercing laser beam at an inclination of the plate against the beam. The divergence of z. B. for medical laser application usable Ar ion laser is Θ = 0.5mrad, the beam diameter at 1.5mm. With a focusing lens of focal length f = 20mm, the focus diameter d _f of

d, = f-0 = 10pm. (1)

The largest angle of the laser beam edge against its optical axis is f = 20 mm at 2.15 °. For longer focal lengths, it is even cheaper, d. H. the angle is smaller.

The core diameter of the fibers used for medical applications is 200 ... 600μιη, d. H. a low astigmatism does not interfere with the coupling, the inclination of the focused laser beams are safely within the acceptance angle of 11.5 ° ... 18 ° of the common fibers.

For small slopes, the beam displacement of a plane-parallel plate is given by the formula

r = ά · (1 - Vn) · d (2)

given.

Mean: α = inclination of the plate against the beam

η = refractive index of the plate

d = thickness of the plate

r = displacement of the beam, distance of the focus from the point of penetration of the fiber axis on the fiber entrance surface (see Fig. 3).

With a plate of quartz glass (n = 1.463), the thickness d = 6mm, the position of the focus can be run at plate inclination angles of α <9 ° over the entire fiber entrance surface (r <300 μ \ τ \) . Such large r-areas (and therefore angles) are generally not required because of the fine mechanical adjustment which is good from the outset.

Claims (3)

Claim: 1. Arrangement for coupling a laser beam into a glass fiber, consisting of a laser, a focusing lens, a glass fiber and a holder for the glass fiber, characterized in that all parts of the holder are rotationally symmetrical to the optical axis and between the focusing lens and a fiber to the optical axis rotatable and about an axis perpendicular to the optical axis tiltable, for the laser light-permeable adjustment plate is arranged. 2. Arrangement according to claim 1, characterized in that the adjusting plate is formed planparaliel. 3. Arrangement according to claim 1, characterized in that the adjusting plate is formed plankonkav. For this 1 page drawings Field of application of the invention The invention relates to an arrangement for coupling a laser beam in a glass fiber, consisting of a laser, a focusing lens, a glass fiber and a holder for the glass fiber. It is preferably applicable to the use of lasers in medicine such as laser surgery and laser endoscopy. Characteristic of the known technical solutions A laser beam is imaged on or near the entrance surface of the fiber by means of a focusing lens. It is important that the focus is placed exactly in the middle of the entrance surface. In the known technical solutions complex x-y shifts are used for this purpose. When using rotatable glass wedges (EP 57164) occur due to multiple optical interfaces increased losses and the adjustment is also complicated and cumbersome. Object of the invention The aim of the invention is an easy-to-use, low-loss and accurate adjustment of the laser focus on the glass fiber. Explanation of the essence of the invention The object of the invention is to realize the adjustment using only one optical part. The object is achieved in an arrangement. According to the preamble of the main claim according to the invention by the features of the characterizing part. Preferred developments are described in the subclaims. The use of only turned parts guarantees a high adjustment accuracy during assembly. The remaining adjustment is made by a more or less inclined adjustment plate, which may have a different cross-section as needed to compensate for the small astigmatism occurring due to the inclination. The adjustment plate should expediently be antireflected for the laser wavelength used. There is also the possibility of. to carry out an automatic optimization of the radiation coupling by means of the proposed adjustment. embodiment The invention will be explained in more detail below with reference to the schematic drawings. Show it: Fig. 1: The inventive arrangement Fig.2: A possible embodiment of a rotating and tilting adjustment plate Fig. 3: The course of the laser beam through the adjusting plate In Fig. 1, a laser 7 emits a laser beam 9 along an optical axis 8. At the laser centered on a laser 7 version 1 is provided. About this version 1, a housing 2 is connected to the laser, in which a glass fiber 3, in turn centered, is supported. Furthermore, a centered focusing lens 4 is provided in the housing 2. An adjustment plate 6, preferably a plane-parallel glass plate, is tiltably and rotatably mounted in the housing 2 so that the tilt axis 5 perpendicular pierces the optical axis and the axis of rotation coincides with the optical axis 8. A possible embodiment of the rotation and tilting of the adjusting plate 6 is shown in FIG. 2.